Not to be quoted without prior reference to the authors
© Crown Copyright 2008
Fisheries Research Services Internal Report No 14/08
SURVEY OF SOLWAY COCKLE GROUNDS 2007
T R W Howell, S E B Davis, N A Brown, J Drewery,
H A McLay, P Gibson, L Allen and A Tait
2007
Fisheries Research Services
Marine Laboratory
Victoria Road
Aberdeen AB11 9DB
Survey of Solway Cockle Grounds 2007
SURVEY OF SOLWAY COCKLE GROUNDS 2007
T R W Howell, S E B Davis, N A Brown, J Drewery,
H A McLay, P Gibson, L Allen, A Tait,
Fisheries Research Services, Marine Laboratory
375 Victoria Road, Aberdeen, AB11 9DB
INTRODUCTION
This report provides details of the 2007 survey of the cockle (Cerastoderma edule) stocks of
the Scottish Solway Firth. Although the survey continues a series conducted annually in the
Solway Firth by Fisheries Research Services (FRS) the 2007 survey differs from recent
surveys in the series in a number of respects. The differences are allied to the management
of the fishery and include changes to the timing, the species assessed, the grounds
surveyed. These changes required some modifications to the survey design. Details are
given below.
History of the Fishery and its Management
The present Solway cockle fishery originates from the late 1980s when it developed rapidly
in from small scale hand gathering activity, to a significant mechanised fishery producing in
excess of 4500 tonnes in 1991 (Table 1). During the period from 1990 to 1994 stock
surveys revealed substantial declines in cockle density and abundance, along with poor
recruitment of young cockles. This resulted in the closure of the fishery to vessels on
6 October 1992 and subsequently to tractor dredging from 1 November 1994. The decisions
to close the fishery to mechanical fishing methods were taken in the interests of long term
viability of the cockle stocks and populations of other organisms dependent on them for food.
At that time no action was required to prevent commercial hand gathering of cockles since
such activity was negligible during the early nineties. By 1997, however, the stocks had
recovered to the point where hand gathering became a viable commercial proposition on
some Solway grounds. A steady increase in hand gathering followed until about 1999; it
increased rapidly thereafter. During this period, official statistics were unavailable making
the exact level of hand extraction hard to establish, but in 2000 landings certainly exceeded
2000 tonnes (Howell et al., 2003).
The 2001 FRS survey showed a pronounced fall in the overall biomass since 2000, which
was associated with an increase in overall cockle mortality, including fishing mortality
(Howell et al., 2001b). Against a background of widespread decline in the cockle stocks on
the larger grounds, a possible escalation of unrestricted fishing activity (Howell et al., 2002),
and generally poor recruitment, the existing vessel and tractor dredge closure Orders were
amended by The Inshore Fishing (Prohibition of Fishing for Cockles) (Scotland) Amendment
Order 2001). This extended the prohibition of fishing for cockles within the Scottish Solway
Firth to cover fishing by any method and came into force on 1 January 2002. In 2005 a
further amendment to the Inshore Fishing (Prohibition on Fishing for Cockles) (Scotland)
was required to remove any doubt about the Scotland/England border and this came into
force on 9th March 2005 (Davis et al., 2005).
Since the late 1990s it was increasingly apparent that some form of locally based
management would be advantageous for the Solway cockle fishery, not least because of the
number of locally contentious issues involving the fishery and its partial coverage by Special
Protection Area (SPA) and Special Area of Conservation (SAC) designation. A fisheries
2
Survey of Solway Cockle Grounds 2007
Regulating Order (RO) was identified as the most suitable mechanism to provide the kind of
responsive local management envisioned. After a protracted consultation process involving
the formulation of a management plan a RO was granted under The Solway Firth Regulated
Fishery (Scotland) Order 2006 (SI 2206 No 57) on 13 March 2006. This delegated
responsibility for managing the cockle fishery to the Solway Shellfish Management
Association (SSMA), a local partnership established specifically for this purpose.
Management measures include the issuing of licences and the opening and closing of the
Fishery seasonally. An associated Order, The Inshore Fishing (Prohibition of Fishing for
Cockles) (Scotland) Order 2006, was made around the same time to lift the restrictions
which had been put in place previously. Under the Regulating, Order the SSMA initially
issued 100 licences to hand gatherers, 6 licences to fishing vessels and (on a trial basis) one
tractor dredging licence. A Total Allowable Catch (TAC) for the fishery, based on scientific
advice, was divided between licence holders with tonnage distributed amongst the three
main fishing methods in accordance with the agreed management plan. After a successful
period of fishing the fishery was closed by the SSMA on 28 April with the intention of
allowing new cockle spat to settle undisturbed. The fishery was reopened to licence holders
on 13 November 2006 using TACs calculated on updated scientific advice. For the first time
this advice took into account the feeding requirements of important shorebird populations
within the SPA, as determined by a simple ration model (West, 2006). The fishery closed on
15 April 2007.
Shore Based Surveys
Shore based surveys of Solway cockles continued after the 1992 closure so that fluctuations
in the stock could be monitored. Following a period of poor recruitment, the lowest biomass
of older cockles of exploitable size was recorded during the 1996 survey. However, the
same survey also showed signs of improved numbers of one-year-old pre-recruits (Howell
et al., 1996). These contributed to an increase in the biomass of commercially aged cockles
(two years and older) in 1997 when there were further signs of improving recruitment, with
one year-olds from the 1996 settlement accounting for about 79% of abundance. The 1996
year class went on to make a significant contribution to the exploitable stock in 1998 and
1999. Although there was poor settlement in 1997, an improved settlement in 1998 survived
to provide about two thirds of the overall Solway cockle abundance in 1999. By 2000,
despite some broadening of the age structure, the overall Solway biomass was largely
maintained through the continued survival of the 1996 and 1998 year classes on one
ground, and there was evidence of only modest recruitment in 1999.
As indicated above, the 2001 survey indicated limited recruitment from the 2000 year class
and declining stocks reliant on adult cockles remaining from the 1998 settlement. However,
during the winter of 2001/2002 the first indications of a large 2001 settlement emerged from
an independent survey, commissioned by the Solway Shellfish Hand Operators Federation
(SSHOF) and later confirmed by the 2002 FRS survey carried out in April/May. In 2003, the
FRS survey showed that the 2001 year class had continued to experience good survival and
growth contributing to a substantial increase in overall biomass. By 2004 the 2001 year
class experienced some mortality but this was offset by good growth so that there was a
negligible drop in the overall biomass in the Solway from 33926 tonnes to 33872 tonnes. In
2005 the still dominant 2001 year class experienced increased mortality which, although
partially offset by good growth, led to a decline in the total biomass from 33872 tonnes in
2004 to 19305 tonnes in 2005. On the grounds covered by the FRS surveys recruitment
was comparatively low between 2001 and 2006 which, along with further mortality of the
2001 year class, led a decline in the overall biomass to 8469 tonnes by 2006.
During 2006 the SSMA commissioned Marine Ecological Surveys Limited (MESL) to carry
out an additional survey of the reformed Carsethorn bank. This survey, carried out in
September, estimated 4559 tonnes of cockles (MESL, 2006) on Carsethorn which, assuming
3
Survey of Solway Cockle Grounds 2007
the FRS April/May estimate remained static, gave an overall biomass of 13028 tonnes. In
2007 the SSMA commissioned another survey by MESL, carried out between 29 May and 1
June, to assess the abundance bivalves, to estimate cockle mortality on the Carse Sands,
and to provide information for cockle growth rate calculations. This information was required
for the development of an individual-based shorebird interaction model which is being
developed by Dr. Richard Stillman of Bournemouth University. The model uses information
from the MESL survey along with cockle and other bivalve data from the 2007 FRS survey
described in this report.
The 2007 FRS Survey
As indicated above there were substantial changes to the FRS survey in 2007 driven largely
by the requirements of the individual-based shorebird interaction model which is used in
setting the TAC for the fishery. The changes were threefold: the timing of the survey, carried
out later in the year from 29 July to 7 August as compared with April/May; the survey would
include all bivalves; and Wigtown Bay would not be surveyed to allow time for surveys on
Carsethorn and also Arbigland – a previously un-surveyed area of the upper Firth where
cockles stocks have been reported. As in previous FRS shore-based surveys All Terrain
Vehicles (ATVs) were used to collect samples during periods of low tide. All bivalves were
sampled at each station using established FRS cockle survey methods therefore the
sampling strategy for all species was based on the distribution of cockles. Two stage
adaptive sampling (Bailey et al., 1998) was used again on the North Bank and Barnhourie
while stratified random surveys were used on all other grounds. The survey method for
targeting sampling effort on the North Bank area (Davis et al., 2004) was further modified for
2007.
SURVEY METHODS
General
The grounds surveyed in 2007 are shown in Figure 1. They were:
(A)
(B)
(C)
(D)
(E)
(F)
(G)
(P)
Barnhourie Bank
North Bank
Carsethorn
Auchencairn Bay
Orchardton Bay
Glenisle
Rough Island
Arbigland
The names used here are those used by cockle fishermen during the era of suction dredge
surveys in the early 1990s and have been retained in survey reports for continuity. The
"Barnhourie" or "Barnhourie Bank", (area A), includes the Barnhourie Bank and the
Mersehead Sands. Similarly, the area referred to collectively as the "North Bank", (area B),
includes the Blackshaw Bank, Priestside Bank, Middle Bank, and North Bank as shown
within the "unsurveyed" region on Admiralty Chart 1346 (2001 edition).
In order to gain safe access to Carsethorn and to transport staff and equipment a cockle
fishing vessel, The Second Degree, was arranged by SSMA. Samples from Glenisle were
collected on foot. Access to Arbigland was arranged through the Arbigland estate.
4
Survey of Solway Cockle Grounds 2007
Computed random sampling positions were fixed by GPS satellite navigation equipment
mounted on the ATVs, or carried by hand. The distribution of sampling stations is shown in
Figure 1 and sampling details for each ground are summarised in Table 2.
Stratified Random Survey Design
Carsethorn (C), Auchencairn (D), Orchardton Bay (E), Glenisle (F), Rough Island (G), and
Arbigland (P)
A conventional stratified random survey was carried out on areas (C), (D), (E), (F), (G), and
(P). For each area a notional grid of squares (strata) was constructed covering the extent of
the cockle ground. Within each stratum one quadrat sample was taken from each of two
randomly positioned stations, the positions were generated computationally prior to the
survey and then located using GPS navigation. All samples were taken using a 0.1 m2
quadrat frame, from which sediment was removed to a depth of up to 100 mm and passed
through a 5 mm mesh sieve. All cockles from the samples were aged, measured and
weighed and the results used in the estimates of abundance and biomass as described
below. All other bivalves from the samples were measured and weighed (age not
determined). The results and procedures used to estimate abundance and biomass are
described in Appendix 3.
Stratified Random Survey Design and Adaptive Procedure
Barnhourie Bank (A)
For Barnhourie Bank the two stage adaptive process employed since 1998 was used. The
first stage consisted of a conventional stratified random survey based on a grid of squares
as described above. The second stage involves allocating additional stations to strata based
on the mean square abundance of 2+ cockles (i.e. two years old and older) observed during
the first stage. This increases the number of samples taken in the areas of highest density.
The number of additional stations sampled in Stage 2 was set to about 25% of the total
number of stations. The cockles gathered in Stage 2 were then aged, measured and
weighed. A full description of these methods is given in the 1998 report (Bailey et al., 1998).
The estimates of abundance and biomass were calculated in the following manner. For
each stratum the mean density (number·m-2) of each age group, of 2 and over, and of all
ages, was raised to the area of the stratum and the stratum variance of the mean calculated.
The estimates were summed across the strata to give an overall estimate of abundance and
variance and the Standard Error (SE) was calculated. The choice of appropriate values of
the t statistic in order to apply confidence intervals is subject to the same caveats expressed
before (Bailey et al, 1998) but a value of two has been assumed throughout this report. The
calculations were repeated using sample weights (derived from the weight-length
relationship described below) to provide estimates of biomass. Again, a full description of
the method is available in the 1998 report.
Modified Stratified Random Survey Design and Adaptive Procedure
North Bank (B)
For 2007 the North Bank was split into 3 areas rather than the two equal halves used in
2006 (Figures 1 and 2c). The eastern area was the same as the eastern half used in 2006
(where abundance was low from 2002 to 2006). Here, strata four times the conventional
size applied to North Bank surveys before 2004 were used, with 2 random samples taken
from each. For 2007 these large strata were also used in the upper (north) western area but
5
Survey of Solway Cockle Grounds 2007
smaller conventionally sized strata were used in the lower (south) western area (Figure 2c).
Three random samples were taken from all accessible western strata, large or small. A
second adaptive stage was carried out in the smaller strata area where relatively high
abundances were found from 2002 to 2006. The rationale for this change in sampling
strategy is explained in the discussion section.
Weight- Length Relationships
The weight-length relationships of cockles from the grounds in the Solway in surveyed in
2007 were compared using analysis of covariance. The relationship for the North Bank was
found to be significantly different from that for the other grounds. Accordingly a separate
relationship was used for North Bank and a single combined relationship was used for the
other grounds:
Wt = 0.000479 Length2.93 (North Bank)
Wt = 0.000319 Length3.07 (All other areas)
RESULTS
General
The distribution of the 732 stations sampled in the 2007 survey is shown in Figure 1. For the
two adaptive surveys, 196 and 50 stations were sampled during stages 1 and 2 respectively
at Barnhourie Bank; and 144 and 50 stations respectively for stages 1 and 2 at North Bank
(West). The area of each sample taken was 0.1.m2. Samples at 386 stations yielded no
cockles and the remaining 346 stations yielded 9848 cockles (Table 2).
For comparative purposes, detailed information on the density, abundance, biomass and
age composition of cockles in each area is presented in Tables 6 and 7 while Figure 5
illustrates the age structure on different grounds. Summaries of the 2007 stock position in
each area and for all areas combined, in comparison with earlier results, are presented in
Tables 8 and 9 and Figures 6 and 7. Table 10 gives an indication of biomass (tonnes) at a
range hypothetical minimum landing sizes. The result tables and figures follow a similar
format to that used in previous reports. Historical biomass and density data are provided for
different grounds in appendices 1 and 2. Details of the other bivalves found on the 2007
survey are given in Appendix 3.
The numbers of cockles in the samples taken in the 2007 survey greatly exceeded those in
2006. However, it should be born in mind that the 2007 survey was conducted in
July/August after the majority of spat settlement is likely to have occurred appearing as
'0'-group cockles in the samples: previous surveys were carried out earlier in the year in
April/May, before any settlement was apparent (Bailey et al., 1998, Davis et al., 2004, 2006,
and Howell et al., 1994, 1995, 1996, 1997, 1999, 2001a, 2001b, 2002, 2003). Therefore this
year’s survey includes information about ‘0’-group cockles (Tables 3 to 7). The later timing
of the survey should also be born in mind when comparing abundance and biomass to
previous surveys.
Barnhourie Bank (A)
The survey of Barnhourie Bank was undertaken using the 2 stage adaptive technique. A
total of 246 stations were sampled overall (Figure 1) of which 124 contained cockles (Table
2). The maximum size of each of the 98 strata was 0.326 km2 and the total survey area was
31.23km2 (Table 2). Spacing between the stations was variable depending on the
6
Survey of Solway Cockle Grounds 2007
randomisation process and the addition of stations to some strata in Stage 2 of the adaptive
process (Bailey et al., 1998). The samples yielded 1400 cockles from 124 stations including
both stages (Table 2) - an average of 11.3 per station.
The distribution of samples in the Stage 1 process is shown in Figure 2a, grid squares with
no symbols indicate inaccessible areas. The symbols indicate presence (triangles) and
absence (crosses) of 2+ year old cockles across the ground and the size of the triangles
indicates the relative abundance of this commercial sized group. The distribution of areas of
higher abundance is clear.
On the basis of these data from the first stage, calculations were made to determine into
which strata the 50 Stage 2 samples should be allocated (Bailey et al., 1998). In the left half
of Table 4a, the calculated values of G are listed in descending order of magnitude for each
additional station, together with its position and the stratum into which it was placed. The
overall pattern of allocation in Stage 2 is shown in Figure 2b where the small numbers
indicate stratum labels and the large, bold figures indicate the number of additional samples
allocated. The right hand side of Table 4a shows the densities of cockles obtained during
Stage 2. The effectiveness of targeting sampling in this manner is illustrated by the fact that
70% of the 50 Stage 2 samples yielded 2 plus cockles, whereas only about 28% of the 196
Stage 1 samples did so.
The combined figures for Stages 1 and 2 provide the basis for the construction of contour
plots shown in Figure 4. Commercial aged (2+) cockles (Figure 4a) were most abundant in
two patches around the mid tide level, one central and the other to the west. Two smaller
low density patches can be seen to the east, also around mid tide level. Slightly further to
the east of this were two dense patches of ‘0’ group cockles. Another dense patch of ‘0’
group cockles was coincident with the central patch of 2+ cockles (Figure 4b).
Estimates of the overall abundance, variance and SE are provided in Table 5a for data from
Stage 1 alone and for both stages combined. The inclusion of second stage samples
reduces the abundance estimates for most ages and, more importantly, also reduces the
variance and SE. The estimate of overall abundance of 2+ cockles is 196.2 +/- 38.2 millions.
Biomass estimates, shown in the lower half of the Table 5a, behave in a similar way. Overall
biomass estimated from Stage 1 alone is 2550.5 tonnes with a confidence interval of +/643.0 tonnes whereas inclusion of Stage 2 samples reduced the estimate to 2070.0 tonnes
and reduced the confidence interval to +/- 446.6 tonnes.
For comparative purposes, data from this area were transferred to the standard format used
in previous surveys (Table 6). Numbers at age for the whole area summed and averaged
across the whole ground gave a higher overall density estimate of 39.8.m2 cockles,
compared to 15.3.m2 in 2006.
The remaining cockles from the 2001 settlement now appear in the 6 years and above (6+)
age group in tables 6 and 7. At a density of 1·m2 6+ cockles provide less than 3% of the
overall abundance and about 15% of the commercial aged cockles, indicating a further
decline in the 2001 year class (Table 6 and Figure 5). The most numerous year class is the
‘0’ group (i.e. the 2007 settlement) accounting for over 70% of the abundance. The 2005
and 2006 settlements, now 1 and 2 year olds, account for just over 20% of the total. The
overall biomass has increased slightly compared to the April/May 2006 survey, from 2840 to
2894 tonnes. One and two year olds provide over half of the biomass with the 6+ age group
providing about one sixth (Table 7).
7
Survey of Solway Cockle Grounds 2007
North Bank (B)
As described in the methods section, the North Bank was divided into three areas. The
lower western area, surveyed using the 2 stage adaptive process, used a stratum size of
0.618 km2; while the upper western and eastern areas were each surveyed with a stratified
random survey design using a stratum size 4 times larger at 2.472 km2. The 52 upper and
lower western strata along with the 11 eastern strata surveyed gave a combined survey area
of 65.55 km2 (Table 2). A total of 228 stations in the eastern, upper western, and both
stages of the lower western survey areas were sampled (Figure 2c). Of these, 113 stations
contained a total of 7063 cockles (Table 2).
The distribution of first stage samples in the lower western areas and the stratified random
surveys in the upper western and eastern areas are shown in Figure 2c. The strata with no
symbols indicate inaccessible areas. The symbols indicate presence (triangles) and
absence (crosses) of 2+ year old cockles across the ground with the area of the triangles
indicating the relative abundance of this commercial sized group. The distribution of areas
with higher abundance is clear.
The combined results for both stages of the lower western, and the single stage upper
western and eastern areas provide the basis for the construction of the contour plots shown
in Figure 4c and 4d. Commercial aged (2+) cockles were found in several patches at the
lower mid tide level to the south and west of the overall survey area (Figure 4c). These low
density patches were dispersed around and to the east of the area where a high density
patch of 2001 year class cockles was found on surveys from 2002 to 2005. Figure 4d shows
the distribution of ‘0’ group and one year olds from the 2006 and 2007 settlements; they
occur at high densities in the same general area as the 2+ cockles apart more dispersed
patches to east at the mid to upper tide level.
Estimates of the overall abundance, variance and SE for the lower western area adaptive
survey from Stage 1 alone and for both stages combined are provided in Table 5b. The
inclusion of second stage samples appears to reduce the abundance estimates for some
ages and reduces the variance and SE giving a 2+ cockle abundance estimate of 68.2 +/18.4 millions. No 2+ cockles were found in the upper western area of the survey (Table 3b).
The abundance estimates for the eastern area of the survey indicate 37.2 million 2+ cockles
with a wide confidence interval similar to the estimate (Table 3a). This has the effect of
widening the overall confidence interval when the abundance estimates for the three areas
are combined, giving overall 2+ abundance estimate of 105.4 +/- 46.6 (Table 5c). Biomass
estimates, shown in the lower half of the Tables 3a, 3b and 5b, behave in a similar way.
Using the revised weight-length relationship the overall two stage lower western biomass
estimate is 6007 tonnes with a confidence interval of +/- 854 tonnes. The addition of the
upper western and eastern biomass estimates (Table 3a) contributes a further 1724 tonnes
to the North Bank total, giving a combined overall biomass estimate of 7731 tonnes, with a
confidence interval of +/- 1453.2 tonnes (Table 5c).
For comparative purposes, the combined east and west survey data were transferred to the
standard format used in previous surveys. Numbers raised to the overall area gave an
overall density for the ground of 189.1 cockles·m-2 (Table 6) compared to 7.9 cockles·m-2 in
2006. This substantial increase in density is explained by very large numbers of ‘0’ group
cockles, which overshadow an improvement in numbers of 1 year olds compared to 2006
April/May survey. The previously dominant 2001 year class is now part of the 6 years and
above (6+) age group in tables 6 and 7 which, as a whole, contributes less than 1% of the 2+
abundance. The overall North Bank biomass has risen from 2207 in 2006 to 7731 tonnes in
2007. This is explained by the substantial increase in the biomass of cockles less that 2
8
Survey of Solway Cockle Grounds 2007
years old: ‘0’ group cockles account for more than 50% of the biomass while the growth of
surviving cockles from the 2006 settlement account for a further 30% of the total.
Auchencairn (D)
A stratified random survey using a maximum stratum size of 0.100 km2 for each pair of
random stations was carried out on grounds at Auchencairn. The extended coverage used
in 2006 was retained using strata of the same size. The survey area contained 37 strata
giving a survey area of 3.457 km2, taking part strata into account, compared to 3.19 km2 in
2006. (Table 2, Figure 1). The number of sampling stations was 74 of which 29 had cockles
(Table 2). Compared to the 2006 survey results, when the samples yielded 148 cockles from
36 stations, the 2007 results show a decrease to 76 cockles from 37 stations (Table 2). This
is an average of 2.1 cockles per station as compared to 4.1 in 2006.
The distribution of the Auchencairn survey samples, over the ground and within the
numbered strata, is shown in the lower left part of Figure 3a. The strata with no symbols
indicate inaccessible areas. The symbols indicate presence (triangles) and absence
(crosses) of 2+ year old cockles across the ground with the area of the triangles indicating
the relative abundance of this commercial sized group. Estimates of overall abundance,
variance and SE from the stratified random survey are provided for this ground and the
results are shown in Table 3d. The estimate of overall abundance of 2+ cockles is 22.8 +/9.2 millions. Biomass estimates, shown in the lower half of Table 3d, behave in a similar
way. Overall biomass estimated is 331 tonnes with a confidence interval of +/- 151 tonnes.
For comparative purposes, data from this area were transferred to the standard format used
in previous surveys. Numbers raised to the overall area gave an overall density for the
ground of 10.7 cockles·m-2 (Table 6) compared to 21.0 cockles.m-2 in 2006. This represents
a decrease in abundance with ‘0’ group and two year olds from the 2005 year class the most
numerous. These two year olds, along with 6+ cockles contributing most to the estimated
overall biomass which has fallen from 126.9 to 95.8 tonnes.km-2 giving a decrease in total
biomass of just over 30 tonnes for the slightly larger survey area (Table 7).
Orchardton (E)
A stratified random survey with a maximum stratum size of 0.242 km2 for each pair of
random stations was carried out at Orchardton. The total area of the 6 strata sampled was
1.032 km2; similar to the previous year. Eight of the 12 stations yielded a total of 17 cockles
(Table 2) compared to 16 from 8 stations in 2006, so the average number of cockles to
remains at about 2 per occupied station.
The distribution of stratified random survey samples over the ground and within the
numbered strata is shown in the left of centre area in Figure 3a. The strata with no symbols
indicate inaccessible areas. The symbols indicate presence (triangles) and absence
(crosses) of 2+ year old cockles across the ground with the area of the triangles indicating
the relative abundance of this commercial aged group.
Estimates of overall abundance, variance and SE from the stratified random survey are
provided for this ground and the results are shown in Table 3e. The overall abundance
estimate for 2+ cockles is 9.6 +/-7.7 millions. The overall biomass estimate, shown in the
lower half of the Table 3e, is 95.4 +/- 74.6 tonnes.
For comparative purposes, data from this area were transferred to the standard format used
in previous surveys. Numbers raised to the overall area gave an overall density for the
ground of cockles 12.6·m-2 (Table 6) compared to10.6 cockles.m-2 in 2006. Over 40% of the
cockles at Orchardton were two year olds which have grown sufficiently since the 2006
9
Survey of Solway Cockle Grounds 2007
April/May survey to offset the declining contribution of older year classes’ to the overall
biomass. This has risen from 58.3 to 102.1 tonnes.km-2 with two year olds contributing
almost half of the total biomass (Table 7).
Glenisle (F)
A stratified random survey was carried out at Glenisle, with a maximum stratum size of
0.165.km2 as introduced in 2006. Coverage of the ground was altered slightly allowing the
inclusion of two part strata to the north west of the area. This had the effect of increasing the
number of strata surveyed from 6 to 8 for each pair of random stations giving an overall area
of 0.659 km2, taking changes to the other part strata into account. Nine out of the sixteen
stations yielded cockles - a total of 33 - giving an average number of 3.7 per station (Table
2). This represents a decrease, compared to 2006, when four stations yielded a total of 78
cockles, 19.5 per station.
The distribution of the 16 stratified random survey samples over the ground and within the
numbered strata is shown in the hatched area in Figure 3a. The symbols indicate presence
(triangles) and absence (crosses) of 2+ year old cockles across the ground with the area of
the triangles indicating the relative abundance of this commercial sized group.
Estimates of overall abundance, variance and SE from the stratified random survey are
provided for this ground and the results are shown in Table 3f. The estimate of overall
abundance is 17.5 millions which should be viewed with caution because the confidence
interval appears to exceed the estimate. This also applies to the overall biomass estimate of
28.5 tonnes shown in the lower half of Table 3f.
For comparative purposes, data from this area were transferred to the standard format used
in previous surveys. The numbers raised to the total survey area give a density estimate for
the ground of about 26.6 cockles·m-2 (Table 6) compared to 65.6 cockles.m-2 found in 2006.
The April/May 2006 survey found high numbers from the 2005 settlement and 6+ year old
cockles. These age groups have both declined sharply and are now outnumbered by ‘0’
group and 1 year olds which together account for 85% of the abundance. The decline of 6+
cockles, in particular, explains the decrease in overall biomass from 439 to 28.5 tonnes
(Table 7).
Rough Island (G)
A stratified random survey with a maximum stratum size of 0.165 km2 for each pair of
random stations was carried out at Rough Island. The total area of the 16 strata sampled
was 1.859 km2, taking part strata into account. Ten of the 28 stations yielded a total of 57
cockles compared to 24 from 38 stations in 2006 (Table 2) and the average number per
station rose from 2.4 per station in 2006 to 5.7 per station in 2007.
The distribution of stratified random survey samples over the ground and within the
numbered strata is shown in the upper right area in Figure 3a. The strata with no symbols
indicate inaccessible areas. The symbols indicate presence (triangles) and absence
(crosses) of 2+ year old cockles across the ground with the area of the triangles indicating
the relative abundance of this commercial sized group. The hatched area relates to Glenisle
and was excluded from the Rough Island assessment.
Estimates of the overall abundance, variance and SE are provided for this ground and the
results are shown in Table 6 then the estimate of overall abundance of cockles is 14.9 +/12.4 millions. Biomass estimates, shown in the lower half of the Table 3g, behave in a
similar way giving an overall biomass estimate of 107.5 +/- 89 tonnes.
10
Survey of Solway Cockle Grounds 2007
Estimates of overall abundance, variance and SE from the stratified random survey are
provided for this ground and the results are shown in Table 3g. The overall abundance
estimate for 2+ cockles is 9.4 with a confidence interval close to the estimate. The overall
biomass estimate, shown in the lower half of the Table 3g, is 139.5 +/- 115.7 tonnes.
For comparative purposes, data from this area were transferred to the standard format used
in previous surveys. Numbers raised to the total survey area gave an increased overall
density for the ground of about 24.1 cockles·m-2 (Table 6) compared to 6.8 cockles.m-2 in
2006. Over 75% of the 2007 abundance were ’0’ group cockles with 3 and 6+ cockles
accounting for just under 75% of the commercial aged cockles. Because of the high
proportion of ‘0’ group cockles the large increase in numbers is not reflected in the increase
in the estimated biomass per unit area from 48.7 tonnes·km-2 in 2006 to 75.0 tonnes·km-2 in
2007 (Table 7).
Carsethorn (C)
The survey of Carsethorn was undertaken using a stratified random design limited to the
main bed to the west of the river Nith channel (Figure 1). A total of 70 stations were
sampled of which 44 contained cockles (Table 2). The maximum size of each of the
35 strata was 0.128 km2 giving a total survey area of 4.48 km2 (Table 2). The samples
yielded 1153 cockles from 44 stations (Table 2), an average of 26.2 per station.
The distribution of the Carsethorn stratified random survey samples over the ground and
within the numbered strata is shown in Figure 3b, grid squares with no symbols indicate
inaccessible areas. The symbols indicate presence (triangles) and absence (crosses) of 2+
year old cockles across the ground and the size of the triangles is indicative of relative
abundance of this commercial sized group.
The figures from the stratified random survey provide the basis for the construction of
contour plots shown in Figure 4e and 4f. Commercial aged (2+) cockles (Figure 4e) were
most abundant around the mid tide level in a dense patch, to the east and south of this were
two less dense patches. ‘0’ group and one year old cockles were widespread and
particularly dense at mid tide level in the middle and to the west of the ground.(Figure 4f).
Estimates of abundance, variance and SE are provided for this ground, and the results are
shown in Table 3c. The abundance estimate for 2+ cockles is 34.8 +/- 13.5 millions.
Biomass estimates are shown in the lower half of the Table 3c with an overall biomass
estimate for the area of 850.6 +/- 222.9 tonnes.
For comparative purposes, data from this area were transferred to the standard format used
in the other surveys (Table 6). Numbers at age for the survey area summed and averaged
across the ground gave an overall density estimate of 164.5 cockles·m-2 of which over 85%
were ‘0’ group and a further 10% were 1 year old. Of the remaining cockles those of six
years and older were the most prevalent accounting for nearly 60% of the 2+ numbers, and
over half of the 2+ biomass(Tables 6, 7, and Figure 5). One year old cockles accounted for
over a third of the total biomass.
Arbigland
A stratified random survey design was used at on the Arbigland ground situated to the south
of Carsethorn (Figure 1). The maximum size of the 29 strata sampled was 0.223 km2 giving
a total survey area of 5.284 km2, taking part strata into account (Table 2). A total of
58 stations were sampled of which 9 contained cockles. The samples yielded 9 cockles
from 58 stations (Table 2), about one cockle for every six stations.
11
Survey of Solway Cockle Grounds 2007
The distribution of the Arbigland stratified random survey samples over the ground and
within the numbered strata is shown in Figure 3b, grid squares with no symbols indicate
inaccessible areas. The symbols indicate presence (triangles) and absence (crosses) of 2+
year old cockles across the ground and the size of the triangles is indicative of relative
abundance of this commercial sized group.
Estimates of abundance, variance and SE are provided for this ground, and the results are
shown in Table 3h. The abundance estimate for 2+ cockles is 8.1 +/- 3.1 millions, shown in
the upper half of the table, while the overall biomass estimate of 148.6 +/- 60.8 tonnes for
the area is shown in the lower half of the Table.
For comparative purposes, data from this area were transferred to the standard format used
in the other surveys (Table 6). Numbers at age for the survey area summed and averaged
across the ground gave an overall density estimate of 3.6 cockles·m-2 of which 57% were ‘0’
group or 1 year old cockles. Just over 38% of the 2+ cockles were two years old. Over 90%
of the overall biomass was made up of 2, 4 and 6+ year old cockles. (Tables 6 and 7, and
Figure 5).
DISCUSSION AND CONCLUSIONS
Background
The decision to adopt a locally based management system for the Solway cockle fishery was
well-founded. Previously management, although well informed and intended, was remote
from the Solway and regulation was achieved largely by legislation under the Inshore Fishing
Act. This proved increasingly unwieldy given the fluctuations of the cockle stocks, their
potential commercial value to the various fishing interests, and an increasing need to
harmonize fishing activity with natural space development in the Solway. Locally based
management is delivered by a fishery Regulating Order (RO) made under section 1 of the
Sea Fisheries (Shellfish) Act 1967. A specially set up local partnership, the Solway Shellfish
Management Association (SSMA) applied for the RO. As part of the application process the
SSMA were required to submit a comprehensive management plan to the Scottish Executive
(as was) for evaluation. The management plan set out the justification for the Regulating
Order and included detailed proposals for managing the cockle fishery in the context of the
existing nature conservation interests in the area. Additionally, because part of the fishery is
subject SPA and SCA designation, SEERAD - now Scottish Government Marine Directorate
– were required to carry out an Appropriate Assessment (AA) under the Habitats Directive
(EEC, 1994). In 2006, after a thorough consultation process, a RO was granted to the
SSMA. The SSMA is a limited company (Company Number 211971) with a Board Directors
that includes representatives from Dumfries & Galloway Council, Scottish Natural Heritage,
RSPB Scotland, and local Fishermen’s Associations representing the different fishing
methods. The Board is therefore suitably constituted to provide a flexible responsive
management system able, and required, to comply with the Solway’s various nature
conservation designations. There are a number of these. The upper Solway is: a SPA and
a SAC; a Ramsar site; and a Site of Special Scientific Interest (SSSI). In addition, the
Wigtown Bay cockle grounds in the outer Solway are within the UK’s largest Local Nature
Reserve (LNR).
In March 2006 the fishery was reopened under the Regulating Order allowing fishermen with
a SSMA Regulating Order licence to fish for cockles. The SSMA initially issued 100 licences
to hand gatherers, 6 licences to fishing vessels and (on a trial basis) one tractor dredging
licence. A Total Allowable Catch (TAC) for the fishery, based on scientific advice, was
divided between licence holders with tonnage distributed amongst the three main fishing
methods in accordance with the agreed management plan. After a successful period of
12
Survey of Solway Cockle Grounds 2007
fishing the fishery was closed by the SSMA on 28 April to allow cockle spat to settle
undisturbed. In order to reopen the fishery an updated Appropriate Assessment was
required. The Appropriate Assessment concluded that the feeding requirements of
important shorebird populations should subsequently be taken into account when TACs for
cockle fishery are set. In 2006 this was accomplished by modelling oystercatcher,
Haematopus ostralegus (L), and knot, Calidris canutus (L) populations / food requirements,
against the availability of key food items, including cockles, using a simple ration model
(West, 2006). This made use of data from the 2006 FRS survey and other sources. The
fishery was reopened to licence holders for the period from 13 November 2006 to 15 April
2007. For future TAC calculations an individual-based shorebird interaction model is being
developed by Dr. Richard Stillman of Bournemouth University.
The later timing of the FRS survey in 2007 was a result of the importance placed by SGMD
and the SSMA on the shorebird interaction model in decisions to reopen the fishery and for
setting TACs. Previously the FRS survey results were used directly in these decisions, but
in 2007 the survey results were used as input data for the shorebird model as well. The data
required include “0” group cockles - an important food resource for some shorebirds - and it
was therefore necessary to assess “0” group availability before the winter. The preferred
timing of previous FRS surveys was in the spring before cockle settlement was apparent. It
had been found in the past that large numbers of “0” group cockles in the samples increased
handling time considerably, yet their presence had little predictive value proving unreliable
as an indicator of future year class strength and adult stock size. This was due to the
variability of first winter mortality which can be extremely high (Chapman et al, 1994) - and to
which shorebirds contribute. The shorebird model also requires data on other bivalve
species forming an important component of shorebird diet. Since little was known about the
distribution, abundance and biomass of other bivalve species present in the Scottish Solway
Firth these were also included in the FRS 2007 FRS survey.
A further requirement for the survey in 2007 was coverage of two additional areas. One
area was on the Carsethorn bank, reformed since the dramatic erosion of original beds
(Bailey et al, 1992) and upon which recent surveys by MESL in 2006 and 2007 have
confirmed the presence of cockle stocks. This area was not accessible from the shore so a
vessel to transport staff and equipment to the banks was required, and this had to be taken
into account in planning the 2007 survey. To gain as full a picture as possible of bivalve
stocks in the upper Firth the Arbigland area was also included and was accessible from the
shore. Because of the need to survey these additional areas within the restricted period of
spring tides and the large amount of sample material to process, it was decided to focus on
areas within or adjacent to the SPA in the upper Firth and a survey of Wigtown Bay was not
carried out in 2007. Although this has implications for FRS’ cockle survey as a whole it was
justified in relation to the shorebird model because Wigtown is considered to be beyond the
feeding range of the modelled shorebird populations (SNH pers com). Apart from its LNR
status, a number of factors make Wigtown Bay less attractive for cockling, including difficult
access from the shore and relatively poor cockle growth rates: it has not been legally fished
since the RO came into force. Its sediments do however, contain a substantial proportion of
the Scottish Solway cockle spawning stock biomass, about 30% in 2006 (Davis, 2006), and
for this reason it is important that Wigtown Bay is included in future surveys.
Additional modifications to the North Bank survey design were introduced with the aim of
improving sampling efficiency on this, the largest, survey area to free up time and resources
required for other aspects of the 2007 survey. The modifications involved sub-dividing the
western half of the North Bank area so that larger strata were used in the upper tidal reaches
where consistently low abundances have been found on previous surveys. This enabled
sampling effort to be concentrated on the remaining western sub division, where the second
adaptive phase of the survey was carried out. This strategy did not reduced the precision of
the overall North Bank abundance estimate when comparing the standard error of the 2006
13
Survey of Solway Cockle Grounds 2007
estimate ( 551.2 million cockles ± se 183.4) to the standard error of the much larger 2007
estimate (12399.4 ± se 3618.3). The substantial increase in abundance is explained by the
high numbers of “0” group cockles settling in 2007. The next survey of the North Bank
should consider modifications of the design to take account of the wider dispersion pattern
found in 2007 (Figures 4c and 4d). This will maintain the flexible approach to survey design
while using comparable methods which allow measures of precision to be attached to the
survey estimates.
Stock Trends
This series of annual cockle surveys in the Solway Firth extends back to 1990 and
constitutes an extensive data set that provides detailed information on spatial and temporal
stock changes of the cockle beds within the Solway area. Natural changes in the distribution
of sediment on the beds mean that the area surveyed can differ from year to year. To allow
comparison, estimates of the overall density and biomass.km2 have been included to provide
a comparative indicator of stock condition between grounds and between years. In 2007,
732 samples were collected from the grounds with a total survey area exceeding 113km2
(Table 2), a smaller area than the 121km2 of the grounds surveyed in 2006. Although the
reduction in the total area surveyed is not large it conceals notable changes to survey as a
whole. For the first time in this series Wigtown Bay was not surveyed whereas Carsethorn
Bank and Arbigland were. It is important that these changes are be born in mind when
looking at the most recent trends.
As in previous Solway cockle reports, the findings for 2007 are examined in the context of a
time series of data going back to 1990. Changes in the cockle stock within each area, and
for all grounds combined, are summarised in Tables 8 and 9 and illustrated in Figures 6 and
7. The three main Scottish grounds, were all showing signs of increasing biomass from a
low point in the 1990s. This process continued until the estimated biomass on the Wigtown
and North Bank grounds reached a peak in 1998 and began a decline that continued until
2001. At Barnhourie there was a sharp decline in biomass between 2000 and 2001. Since
the mid 1990s the stock on the smaller beds fluctuated much more but with a discernible
peak in 1999 followed by a decline that continued until 2001. In 2001 a very large cockle
settlement occurred in the Solway Firth. The strength of this exceptional year class became
apparent in 2002 when the FRS survey indicated a high density of under-aged cockles
(Table 9) distributed widely over the Scottish Solway grounds. The good growth and survival
of this year class between 2002 and 2003 were largely responsible for the increase in
biomass on all grounds, except Orchardton, and the substantial increase in overall biomass
in 2003. In 2004 the mortality of the 2001 year class was found to have varied over the
grounds but was highest on the North Bank where over 60% of the known Scottish Solway
cockle biomass was located. The mortality was offset by good growth rates with the result
that there was remarkably little change in the estimated biomass between 2003 and 2004:
33926 tonnes in 2003 compared to 33872 tonnes in 2004 (Table 9). In 2005 however,
despite continued growth, the overall biomass declined to 19305 tonnes which was
attributed largely to increased mortality of the 2001 cohort on Wigtown, Barnhourie, and
North Bank. The increased mortality was caused by a combination of natural mortality and
fishing mortality, which occurred despite the fishery being closed (Davis 2006). By the 2006
FRS survey indicated a further decline to 8469 tonnes of which 7740 tonnes consists of
cockles of 2 years old or more distributed on Barnhourie (34%), North Bank (24%), Wigtown
(30%), and the remaining 12% distributed over the smaller grounds. The decline was, again,
due to mortality of older cockles, particularly from the 2001 year class on the North Bank and
also on Barnhourie. In contrast the biomass on Wigtown remained fairly stable benefiting
from good settlement in 2004 and relatively low mortality of the 2001 year class compared to
the other grounds. A survey of the reformed Carsethorn Bank also took place in 2006. This
survey, commissioned by the SSMA was conducted by Marine Ecological Surveys Limited
(MESL) and carried out in September, estimated 4559 tonnes of cockles (Newell, 2006) on
14
Survey of Solway Cockle Grounds 2007
Carsethorn. The time elapsed since the 2006 FRS survey means that the overall biomass of
13028 tonnes, obtained by adding the two overall estimates together, should be viewed with
caution in the absence of information on growth and mortality rate in the intervening period.
The 2007 Survey
For the first time all bivalves species were included in FRS’ 2007 survey. In addition to
cockles, eight species were found: Thin tellin, Angulus tenuis (da Costa); Banded wedge
shell, Donax vittatus (da Costa); Bean-like tellins, Fabulina fibula (Gmelin); Macoma,
Macoma balthica (L); Sand gaper, Mya arenaria (L); Common mussel, Mytilus edulis (L);
Peppery furrow shell, Scrobicularia plana (da Costa); and Spisula subtruncata (da Costa).
Excluding cockles, the highest bivalve species diversity was found on Carsethorn where 6
other species were found; the lowest was at Rough Island with only two species in addition
to cockles recorded. Macoma (also know as the Baltic tellin), was by far the most abundant
‘other bivalve’ species accounting for 92% of the other bivalve species abundance over the
whole survey area. Mussels accounted for 6%, the thin tellin 1% and the remaining species
accounted for 1% in total. Macoma were found at 430 stations out of the 447 stations where
other bivalves were recorded and were more common than cockles, which were present at
346 stations. The overall abundance estimate for macoma was 15479 millions, slightly
higher than for cockles, with an estimated biomass of 7245 tonnes. Further details of
macoma and the other bivalve species can be found in appendix 3.
The overall biomass estimate for cockles the 2007 survey was 12225 tonnes, as compared
with 8469 tonnes in 2006. The 2007 commercial biomass (in the context of this report the
term “commercial” refers to cockles of 2 years old or more) was estimated as 4474 tonnes
compared to 7740 tonnes on the 2006 FRS survey which appears to suggest a sharp
decline. However, the later timing and the different areas covered in 2007 mean that the
figures are not directly comparable. For example, included in the 2007 commercial biomass
are 405 tonnes from Carsethorn and 138 tonnes from Arbigland; areas which were not
surveyed by FRS in 2006. Conversely, missing from 2007 are data from Wigtown Bay which
in April 2006 had an overall biomass of 2408 tonnes. Historically this area has tended to
have a more stable age structure and relatively slower growth compared to other Solway
grounds. Uniquely, in 2006 Wigtown Bay had a particularly strong 2004 year class which as
2 year olds accounted for nearly 40% of the 2006 Wigtown biomass with good potential for
further increase in 2006 and 2007, even allowing for slower growth. Additionally, one year
old cockles from the 2005 year class provided over a quarter of the overall Wigtown
abundance. Provided that the mortality of the 2004 and 2005 year classes have not been
unusually high in the intervening period, it is probable that the 2007 Wigtown Bay
contribution to the overall Solway biomass would be at least as high as in 2006.
In the areas that were surveyed in 2007 most of the commercial biomass was located on
Barnhourie with 2070 tonnes (46%) and North Bank with 1299 tonnes (29%) more widely
dispersed over this large ground than in previous years. Of the smaller areas Carsethorn
had 405 tonnes (9%), Auchencairn 323 tonnes (7%) with the remaining areas 377 tonnes
(8%) distributed between them. One of most striking results of the survey was the high
numbers of “0” group cockles present in August 2007 accounting for 91% of the overall
cockle abundance and 37% of the biomass. Most of these juveniles were found in very
dense patches distributed over the eastern and western areas of the North Bank. Although
less abundant than on the North Bank, substantial numbers of juveniles were also found on
the Carsethorn and Barnhourie grounds.
The changes to the timing of the survey and the inclusion of all bivalves provided useful new
information, notably the abundance “0” group cockles and macoma. The individuals were
small: “0” group cockles ranged in mean size from 7.60mm (± sd 1.44) to 8.98mm (± sd
1.80) while macoma (all ages) ranged from 8.74mm (± sd 2.52) to 11.91mm (± sd 2.10) in
15
Survey of Solway Cockle Grounds 2007
the areas surveyed. However, the abundance of both were high giving a biomass estimate
of 4486 tonnes for “0” group cockles and 7245 tonnes for macoma. These data were
considered to of particular importance to the shorebird interaction model. They were
arranged into a suitable format and made available for inclusion into the model being
developed by Dr. Richard Stillman of Bournemouth University. The results of this work are
reported elsewhere.
The 2006-7 Fishery
After consideration of scientific advice based on FRS and MES survey data along with the
shorebird feeding requirements as calculated using the West ration model, a maximum TAC
of 2,500 tonnes was set for a season lasting from 13 November 2006 to 15 April 2007. The
minimum landing size (mls) remained at 30mm for all areas except Carsethorn where it was
27mm. The SSMA regulated grounds fished previously reopened at the start of the season
and the Carsethorn Bank opened a week later, on 20 November. As before specific areas
were assigned to the three permitted fishing methods: hand gathering took place on
Carsethorn Bank and a designated area on the eastern part of Barnhourie; vessel dredging
took place on the North Bank and Glenisle; tractor dredging took place on a designated area
on the western part of Barnhourie. Hand gathering continued on Carsethorn until the end of
January 2007 and on Barnhourie until the last day of the season on 15 April. Dredging by
vessels using suction or elevator dredges continued on the North Bank until the SSMA
closed area on 15 February. The closure followed discussion with the vessel skippers and
was prompted by concerns about fishing intensity and confirmed by the Vessel Monitoring
System (VMS). Glenisle was fished by two vessels using elevator dredges during the
season. The single tractor dredge worked from the beginning of the season until the first
week in January. While the grounds were open a total 637 tonnes (live weight) were landed
by all methods. Hand gatherers landed 254 tonnes from Carsethorn Bank, 43 tonnes from
Barnhourie, and 6 tonnes from unspecified areas. Vessels landed 237 tonnes from North
Bank and 80 tonnes from Glenisle. The tractor dredger landed 16 tonnes from Barnhourie
(SSMA pers com).
Management Considerations
The 2007 FRS survey has provided a more complete picture of the bivalve distribution and
abundance on the Scottish side of the Solway Firth. However, management advice for the
commercial cockle fishery in the area is required to take into account the feeding
requirements of important shorebird populations within the SPA. Although much of the raw
data required to run the individual-based shorebird interaction model has been provided by
FRS, the scientific expertise required to run the model resides elsewhere. For this reason
the final management advice for this fishery is no longer provided in this report alone.
However, for consistency with earlier FRS cockle survey reports, we include below
comments made on the basis of single spices considerations.
The overall biomass of cockles of all ages has shown an increase from 8469 to 12225
tonnes (allowing for the changes in survey timing and areas covered) but a substantial
proportion of these are “0” group cockles overshadowing a reduction in commercial aged
cockles compared to 2006. Table 10a gives an indication of the biomass in August 2007
above a range of hypothetical minimum sizes. It is provided for comparison with the
presentation of previous years’ survey results with the figures calculated in a similar way
using the nominal strata area for each ground. As before, the table indicates the total
available biomass for a particular MLS for each ground. Note that these figures are not
cumulative for each size, thus, for example, an estimated 1,170 tonnes of cockles of 30mm
and larger were available on Barnhourie in August 2007.
16
Survey of Solway Cockle Grounds 2007
On the two major grounds surveyed the biomass of cockles at 30mm and above decreased
from 1625 to 1170 tonnes on Barnhourie and from 1344 to 1074 tonnes on North bank
between 2006 and 2007 (Table 10a). For these two areas the contour plots for 2+ cockles,
which include cockles of less than 30mm, suggest that 30mm cockles are more widely
dispersed in 2007 than in 2006, particularly on the North bank (Figures 4a and 4c). Table
10a also indicates that at 30mm and above, Auchencairn has a further 261 tonnes and
Carsethorn 262 tonnes of cockles and the remaining grounds 307 tonnes between them.
Table 10b gives an indication of 22.5% and 30% of available biomass above a hypothetical
25mm and 30mm minimum landing size for each ground surveyed which might previously
been available to the fuishery. Without taking the shorebird feeding requirements into
account, at present declining adult cockle stock levels a conservative strategy of removing
22.5% of cockles 30mm and larger would be recommended. Adopting this strategy on
Barnhourie, North Bank, Auchencairn and Carsethorn would give a biomass of 623 tonnes.
This approach would leave a larger spawning stock on the grounds while exploiting more
valuable cockles of 30mm and above. An additional consideration is that a high proportion
these 30mm plus cockles are already old, and are liable to increased natural mortality as
they grow older.
Regarding recruitment to the Solway cockle stocks the high abundance of “0” group cockles
found on the survey indicates the settlement of another substantial year class. However, its
presence as an indicator of future stock levels cannot be relied upon and it must again be
emphasised that subsequent natural mortality, particularly over the first winter, can be
extremely high. This is well illustrated by the large settlement of “0” group cockles detected
during a vessel-based survey in December 1992 which had little impact on the stocks
subsequently (Table 9a). To put the size of the 2007 year class into perspective the overall
density in August 2007 before their first winter is not quite as high the density of the 2001
year class as one year olds in April 2002 (Table 9a). Although attention is now focused on
the fate of the 2007 year class it should also be noted that one year old cockles were
reasonably abundant on Carsethorn and North Bank (Table 6, Figure 5).
FRS’ 2006 report highlighted the risk to the sustainability of cockle stocks caused by illegal
fishing. It was concluded that this could only be remedied by effective enforcement. Since
then the enforcement situation has been strengthened under the Police, Public Order and
Criminal Justice (Scotland) Act 2006 under which the Regulating Order grantee or the SFPA
or both can enforce a Regulating Order. This came into force 1 September 2006 clarifying
enforcement responsibilities and helping to provide more effective enforcement of the
Regulating Order.
SUMMARY
a)
A shore-based bivalve survey of Scottish Solway Firth cockle beds was carried out
during periods of low tide in July/August 2007. All bivalves species in the samples
were identified and included in the survey.
b)
Cockle grounds at Carsethorn and Arbigland were included in the survey. Wigtown
Bay was not surveyed.
c)
Quadrat samples of 0.1 m2 were collected at 732 stations within a total survey area
exceeding 113km2.
d)
Cockle stocks were assessed using a modified 2 stage adaptive design using varying
strata size and sample allocation was used on the North Bank. A two-stage adaptive
survey design was used at Barnhourie and stratified random sampling was carried
out on the other areas.
17
Survey of Solway Cockle Grounds 2007
e)
For the areas surveyed the overall biomass estimate for cockles was 12225 tonnes
and the commercial biomass estimate was 4474 tonnes.
f)
The commercial biomass was located on Barnhourie (46%), North Bank (29%),
Carsethorn (9%), and Auchencairn (7%). The remaining 8% was distributed between
other areas.
g)
Large numbers of “0” group cockles were present in August 2007 accounting for 91%
of the overall cockle abundance and 37% of the biomass.
h)
Excluding cockles, eight bivalve species were found on the cockle grounds. The
highest bivalve species diversity was found on Carsethorn where 6 other species
were found
i)
Excluding cockles the most abundant bivalve species was Macoma balthica
accounting for 92% of the other bivalve species abundance. The overall abundance
estimate for macoma was 15479 millions, slightly higher than for cockles, with a
biomass of 7245 tonnes.
j)
The later timing of the survey allowed the inclusion of “0” group cockle data. Cockle
and bivalve abundance and biomass estimates provided by this survey are being
used in an individual-based shorebird interaction model the results of which will be
used to inform management decisions and for setting total allowable catches.
k)
Without taking the shorebird feeding requirements into account and at present
declining adult stock levels a conservative strategy of removing 22.5% of cockles
30mm and larger is recommended.
ACKNOWLEDGEMENTS
The authors would like to thank Jim Smith, skipper of the Second Degree, James Blackett of
the Arbigland Estate, Craig Davis, Eric Armstrong of FRS, and Alex Watson, Tim Ewing and
Alan Cairns of the SSMA for providing their help experience and enthusiasm.
REFERENCES
Anon., Solway Shellfish Management Association Management Plan 2004.
Bailey, N., Howell, T.R.W., Chapman, C.J. and Thain, S. 1992. SOAFD Solway cockle
survey 1991. Scottish Fisheries Working Paper No 19/92, pp.1-7.
Bailey, N., Howell, T.R.W., Davis, S.E.B., Donald,J.W., Fryer,.R., Heine, S. and
Chapman, C.J. 1998. Survey of Solway Cockle Grounds 1998. Marine Laboratory
Aberdeen Report No 7/98.
Chapman, C.J., Howell, T.R.W., Bailey, N., and Thain, S. 1994. SOAFD Solway Cockle
Surveys 1992-1993. Scottish Fisheries Working Paper No 7/94, pp.1-8.
Davis, S.E.B., Howell, T.R.W., Donald, J.W., Drewery J., Tuck I., Ward B., Campbell R. J.,
and Fryer R. Survey of Solway Cockle Grounds 2004. Fisheries Research Services
Internal Report No 15/03
18
Survey of Solway Cockle Grounds 2007
Davis, S.E.B., Howell, T.R.W., Donald, J.W., Drewery J., Harding, M., Ward B., and
Campbell R. J. Survey of Solway Cockle Grounds 2005. Fisheries Research
Services Internal Report No 07/06
European Economic Community, Habitats Directive (92/43/EEC), Article 6(3), Regulation 48,
Habitats Regulations 1994
Howell, T.R.W., McKay, D.W., Chapman, C.J. and Thain, S. 1994. SOAFD Solway cockle
survey 1994. Scottish Fisheries Working Paper No 8/94, pp.1-7.
Howell, T.R.W., Chapman, C.J., Thain, S.E.B. and Hawkins, M. 1995. Survey of Solway
cockle grounds 1995. Scottish Fisheries Working Paper No 7/95, pp.1-8.
Howell, T.R.W., Chapman, C.J., Thain, S.E.B. and Hawkins, M. 1996. Survey of Solway
cockle grounds 1996. Scottish Fisheries Working Paper No 4/96, pp.1-7.
Howell, T.R.W., Davis, S.E.B., Donald, J.W., Bailey, N. and Chapman, C.J. 1997. Survey of
Solway Cockle Grounds 1997. Marine Laboratory Aberdeen Report No 8/97.
Howell, T.R.W., Bailey, N., Davis, S.E.B., Donald, J.W., Hawkins, M. and Chapman, C.J.
1999. Survey of Solway Cockle Grounds 1999. Marine Laboratory Aberdeen Report
No3/99.
Howell, T.R.W., Bailey, N., Davis, S.E.B. and Donald,J.W. 2001a. Survey of Solway Cockle
Grounds 2000. Marine Laboratory Aberdeen Report No 06/01.
Howell, T.R.W., Bailey, N., Davis, S.E.B. and Donald, J.W. 2001b.
Cockle Grounds 2001. Marine Laboratory Aberdeen Report No 16/01.
Survey of Solway
Howell, T.R.W., Davis, S.E.B., Donald, J.W., Weetman A., Drewery J., Martin J., and Bailey,
N., Survey of Solway Cockle Grounds 2002. Marine Laboratory, Aberdeen Report No 06/02
Howell, T.R.W., Davis, S.E.B., Donald, J.W., Drewery J., Martin J., and Ward B. Survey of
Solway Cockle Grounds 2003. Fisheries Research Services Internal Report No 15/03
Newell, R.C., Seiderer, L.J., Beer, N.A. 2006. Cockle Stock Assessment in the Scottish
Solway Firth. Marine Ecological Surveys Limited report.
West, A.D., The Impact of the Regulated Cockle Fishery on Key Bird Species in the Solway
Firth. Centre for Ecology and Hydrology Report to Solway Shellfish management
Association.
19
TABLE 1
a) Tonnes of cockles landed by UK vessels in Scotland from ICES statistical rectangles 38E5
and 38E6 (Solway Firth) (all gears) 1987 - 2001.
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997* 1998* 1999* 2000* 2001*
0
426
708
120
960
350
0
80
0
0
-
-
-
-
-
0
606
1037
629
883
582
0
0
0
0
-
-
-
-
-
0
1357
442
540
1041
1413
0
0
0
0
-
-
-
-
-
209
1159
649
792
1635
18
120
0
0
0
-
-
-
-
-
209
3548
2836
2081
4519
2363
120
80
0
0
550
1300
1500
2000
-
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Total
* Cockles landed during 1997-2001 by one faction of hand gatherers (figures provided by Solway Shellfish Hand Operators Federation)
but have not been recorded in the official statistics. See text. The Fishery was closed to all methods in January 2002
b) Tonnes of cockles landed by SSMA licensees while fishery was open between 13 March and
28 April 2006 by method.
Method
Tonnes landed by Licensees
Hand
255.0
Tractor
24.5
Vessel
204.3
c) Tonnes of cockles landed by SSMA licensees while fishery was open from 13 November 2006
to 15 April 2007 by method.
Method
Tonnes landed by Licensees
Hand
303
Tractor
16
Vessel
317
TABLE 2
Sampling details for the stratified random and adaptive surveys conducted in July/August 2007.
Information is given on the numbers of stations, area of coverage and the sampling levels of cockles,
for each ground. The survey was shore based and largely carried out using ATVs and quadrat
sampling.
Area
Date
May
Method
No
Stations
Grid sq.
area
(km ²)
Overall
Area**
(km ²)
Stations
with
cockles
Cockles
caught
Cockles
aged and
measured
A
B (West)
B (Top)
B (East)
C
D
E
F
G
P
30 Jul - 1 Aug
3,4,6 Aug
04-Aug
03-Aug
01-Aug
02-Aug
02-Aug
29-Jul
29-Jul
05-Aug
Quadrat*
Quadrat*
Quadrat
Quadrat
Quadrat
Quadrat
Quadrat
Quadrat
Quadrat
Quadrat
246
194
12
22
70
74
12
16
28
58
0.326
0.618
2.470
2.473
0.128
0.100
0.242
0.165
0.165
0.223
31.227
29.664
8.687
27.203
4.480
3.457
1.032
0.659
1.859
5.284
124
99
1
13
44
29
8
9
10
9
1400
6800
2
261
1153
76
17
33
57
49
1400
6800
2
261
1153
76
17
33
57
49
113.552
346
9848
9848
Total
A
B
C
D
E
F
G
P
732
Barnhourie
North Bank
Carsethorn
Auchencairn Bay
Orchardton Bay
Glenisle
Rough Island
Arbigland
* Adaptive survey
** Based on the combined area of the strata sampled in a stratified random survey or the combined area of the
strata sampled in the first phase of an adaptive survey.
TABLE 3
Results of stratified random surveys for North Bank (East), North Bank (Top), Carsethorn,
Auchencairn, Orchardton, Glenisle Rough Island and Arbigland. The upper part of each table
shows abundance estimates, variance and standard error (SE) by age group, the lower part
shows the same calculations for biomass (tonnes).
(a) North Bank (East)
0
3078.9
1
111.3
2
24.8
Age
3
12.4
4
0.0
5
0.0
6+
0.0
All ages
3227.4
2+ ages
37.2
2524725.8
2293.4
305.8
152.9
0.0
0.0
0.0
2562031.8
458.7
SE
1588.9
47.9
17.5
0.0
0.0
0.0
1600.6
21.4
Weight (tonnes)
Overall Weight
0
889.2
1
362.1
2
261.7
12.4
Age
3
206.4
4
0.0
5
0.0
6+
0.0
All ages
1719.4
2+ ages
468.1
Overall Variance
193373.2
27052.0
38005.0
42598.8
0.0
0.0
0.0
345815.7
80603.8
439.7
164.5
194.9
206.4
0.0
0.0
0.0
588.1
283.9
0
15.7
1
0.0
2
0.0
Age
3
0.0
4
0.0
5
0.0
6+
0.0
All ages
15.7
2+ ages
0.0
258.4
0.0
0.0
0.0
0.0
0.0
0.0
258.4
0.0
SE
16.1
0.0
0.0
0.0
0.0
0.0
16.1
0.0
Weight (tonnes)
Overall Weight
0
4.8
1
0.0
2
0.0
0.0
Age
3
0.0
4
0.0
5
0.0
6+
0.0
All ages
4.8
2+ ages
0.0
Overall Variance
23.6
0.0
0.0
0.0
0.0
0.0
0.0
23.6
0.0
SE
4.9
0.0
0.0
0.0
0.0
0.0
0.0
4.9
0.0
Abundance
(millions)
Overall Abundance
Overall Variance
SE
(b) North Bank (Top)
Abundance
(millions)
Overall Abundance
Overall Variance
(c)
Carsethorn
0
630.0
1
72.2
2
4.4
Age
3
3.7
4
3.0
5
3.8
6+
19.9
All ages
737.0
2+ ages
34.8
20018.4
138.9
4.5
1.6
2.0
0.8
29.1
22341.6
45.5
SE
141.5
11.8
2.1
1.4
0.9
5.4
149.5
6.7
Weight (tonnes)
Overall Weight
0
140.7
1
305.4
2
54.9
1.3
Age
3
55.9
4
45.2
5
38.0
6+
210.5
All ages
850.6
2+ ages
404.5
Overall Variance
1006.1
3275.1
690.1
403.4
499.7
181.7
3278.7
12425.3
5999.9
31.7
57.2
26.3
20.1
22.4
13.5
57.3
111.5
77.5
Abundance
(millions)
Overall Abundance
0
13.2
1
1.0
2
11.1
Age
3
2.0
4
3.0
5
2.5
6+
4.2
All ages
37.0
2+ ages
22.8
Overall Variance
12.2
0.5
7.5
0.5
2.0
1.8
3.1
40.1
21.0
SE
3.5
0.7
2.7
1.4
1.3
1.8
6.3
4.6
Weight (tonnes)
Overall Weight
0
3.2
1
5.2
2
107.4
0.7
Age
3
28.8
4
43.4
5
44.8
6+
98.5
All ages
331.3
2+ ages
322.9
Overall Variance
0.7
13.7
697.5
185.9
427.4
670.7
1924.0
5666.4
5599.1
SE
0.8
3.7
26.4
13.6
20.7
25.9
43.9
75.3
74.8
(e) Orchardton
Abundance
(millions)
Overall Abundance
0
1.3
1
2.1
2
5.7
Age
3
1.2
4
2.0
5
0.0
6+
0.7
All ages
13.0
2+ ages
9.6
Overall Variance
0.7
2.6
5.4
1.4
2.5
0.0
0.9
26.0
14.9
SE
0.8
1.6
2.3
1.6
0.0
0.9
5.1
3.9
Weight (tonnes)
Overall Weight
0
0.7
1
6.1
2
49.9
1.2
Age
3
12.4
4
25.4
5
0.0
6+
7.7
All ages
102.1
2+ ages
95.4
Overall Variance
0.7
21.0
287.0
155.0
402.9
0.0
96.2
1391.2
1203.5
SE
0.9
4.6
16.9
12.4
20.1
0.0
9.8
37.3
34.7
Abundance
(millions)
Overall Abundance
Overall Variance
SE
(d)
Auchencairn
(f)
Glenisle
Abundance
(millions)
Overall Abundance
0
11.7
1
3.2
2
1.3
Age
3
0.8
4
0.2
5
0.2
6+
0.2
All ages
17.5
2+ ages
2.7
Overall Variance
75.2
3.5
1.1
0.6
0.3
0.1
0.2
110.4
1.5
SE
8.7
1.9
1.1
0.6
0.4
0.4
10.5
1.2
Weight (tonnes)
Overall Weight
0
1.5
1
5.5
2
6.6
0.8
Age
3
6.6
4
1.4
5
3.0
6+
4.0
All ages
28.5
2+ ages
21.5
Overall Variance
1.4
8.5
28.1
45.4
15.1
42.2
60.3
174.0
136.3
SE
1.2
2.9
5.3
6.7
3.9
6.5
7.8
13.2
11.7
0
33.7
1
1.7
2
2.4
Age
3
4.0
4
0.0
5
0.0
6+
3.0
All ages
44.8
2+ ages
9.4
673.2
0.4
0.6
11.5
0.0
0.0
2.5
746.9
21.2
SE
25.9
0.6
0.8
0.0
0.0
1.6
27.3
4.6
Weight (tonnes)
Overall Weight
0
9.8
1
7.0
2
23.4
3.4
Age
3
38.1
4
0.0
5
0.0
6+
61.3
All ages
139.5
2+ ages
122.8
Overall Variance
67.7
5.3
54.1
873.2
0.0
0.0
1211.8
3347.8
2966.1
SE
8.2
2.3
7.4
29.5
0.0
0.0
34.8
57.9
54.5
Abundance
(millions)
Overall Abundance
0
8.6
1
2.3
2
3.1
Age
3
0.0
4
2.4
5
0.3
6+
2.4
All ages
19.1
2+ ages
8.1
Overall Variance
29.7
18.2
2.8
0.0
0.4
0.4
0.4
61.8
2.4
SE
5.5
4.3
1.7
0.6
0.6
0.6
7.9
1.5
Weight (tonnes)
Overall Weight
0
2.2
1
8.2
2
38.9
0.0
Age
3
0.0
4
49.9
5
3.0
6+
46.4
All ages
148.6
2+ ages
138.2
Overall Variance
2.2
218.2
556.4
0.0
128.9
31.5
98.0
925.6
729.4
SE
1.5
14.8
23.6
0.0
11.4
5.6
9.9
30.4
27.0
(g)
Rough Island
Abundance
(millions)
Overall Abundance
Overall Variance
(h)
Arbigland
TABLE 4
Calculated G values for each extra station used in Stage 2 of the Barnhourie and North Bank (West)
adaptive surveys, together with position and stratum in which it was located. Densities of cockles
(numbers.m2) are shown on the right.
a) Barnhourie
Long.
Lat
Number at age (number. m-2)
Extra
Located
G
Station
In
Number
Stratum
1
72
-3.6787
54.8645
0.8679
150
50
0
0
0
0
2
57
-3.6719
54.862
0.7484
0
0
0
0
0
0
3
73
-3.6699
54.8648
0.5358
110
0
0
0
0
0
4
69
-3.7086
54.8654
0.4428
120
0
10
0
0
0
0
130
10
5
72
-3.6811
54.866
0.434
110
40
90
10
0
0
0
250
100
6
57
-3.6778
54.8635
0.3742
80
50
0
0
0
0
0
130
0
7
39
-3.6881
54.8582
0.3587
290
20
30
0
0
0
0
340
30
8
77
-3.6369
54.8649
0.2834
150
0
10
0
0
0
0
160
10
9
73
-3.676
54.8673
0.2679
20
60
30
0
0
0
0
110
30
10
72
-3.6794
54.8667
0.2604
20
60
20
0
10
20
20
150
70
11
57
-3.6712
54.8591
0.2245
0
0
0
0
0
0
0
0
0
12
69
-3.7087
54.8655
0.2214
90
40
0
10
0
0
0
140
10
13
71
-3.6897
54.8643
0.217
120
10
0
0
0
0
20
150
20
14
39
-3.6902
54.8569
0.1793
0
0
0
0
0
0
0
0
0
15
72
-3.681
54.8662
0.1736
110
70
10
10
0
0
10
210
30
16
73
-3.6698
54.8642
0.1607
140
10
0
0
0
0
0
150
0
17
83
-3.7323
54.8712
0.1594
0
50
20
10
10
0
0
90
40
18
85
-3.7157
54.8704
0.1594
0
0
0
0
0
0
0
0
0
19
57
-3.6722
54.8603
0.1497
200
10
20
10
0
0
10
250
40
20
77
-3.6355
54.8684
0.1417
60
20
0
0
0
0
10
90
10
21
69
-3.7074
54.8666
0.1328
50
10
0
0
10
0
10
80
20
22
72
-3.6783
54.8655
0.124
40
10
0
0
0
0
0
50
0
23
50
-3.7446
54.8606
0.1107
0
0
10
10
10
10
10
50
50
24
60
-3.6412
54.8629
0.1107
20
0
10
10
0
0
0
40
20
25
89
-3.6692
54.8731
0.1107
0
0
0
0
0
0
0
0
0
26
71
-3.696
54.8662
0.1085
30
90
0
0
0
0
10
130
10
27
39
-3.6929
54.8581
0.1076
0
0
0
0
0
0
10
10
10
28
73
-3.6718
54.8644
0.1072
170
10
10
10
0
0
0
200
20
29
57
-3.6743
54.8607
0.1069
240
0
10
0
0
0
0
250
10
30
72
-3.6811
54.8675
0.093
20
40
0
10
0
10
20
100
40
31
69
-3.7087
54.866
0.0886
30
20
20
0
0
10
20
100
50
32
77
-3.6353
54.8684
0.085
140
20
10
10
0
0
0
180
20
33
57
-3.6751
54.8629
0.0802
140
40
70
10
0
0
30
290
110
statistic
0
1
2
3
4
5
All
Ages
ages
2+
0
200
0
0
0
0
0
110
0
6
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
83
85
73
72
39
53
55
61
84
71
69
57
72
73
77
50
60
-3.7343
-3.7096
-3.6772
-3.6866
-3.6909
-3.7152
-3.6915
-3.637
-3.7194
-3.6908
-3.7152
-3.673
-3.6807
-3.6731
-3.6294
-3.7384
-3.6402
54.8711
54.8718
54.8684
54.8647
54.8572
54.8594
54.8636
54.8624
54.8695
54.8639
54.8678
54.8616
54.8669
54.8667
54.8663
54.8617
54.8622
0.0797
0.0797
0.0765
0.0723
0.0717
0.0709
0.0709
0.0709
0.0709
0.0651
0.0633
0.0624
0.0579
0.0574
0.0567
0.0554
0.0554
30
0
90
110
0
0
40
20
40
40
20
0
50
100
230
0
0
10
60
30
50
0
0
10
0
0
30
0
0
20
0
20
0
10
20
10
70
0
0
0
30
10
0
20
30
0
10
10
0
10
0
10
0
20
0
0
0
10
0
0
10
30
0
0
0
0
10
0
0
0
0
0
0
0
0
0
0
0
0
0
10
0
0
10
0
0
10
20
0
0
0
0
0
0
20
0
0
0
0
0
0
0
0
0
20
10
0
0
10
0
0
20
0
0
10
0
10
0
0
70
80
250
170
0
0
100
30
40
140
80
0
100
110
260
30
10
30
20
130
10
0
0
50
10
0
70
60
0
30
10
10
30
0
b) North Bank (West)
Extra
Located
Station
Number
In
Stratum
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
19
19
3
4
6
8
13
26
27
31
19
19
3
4
6
8
13
26
27
Long.
-3.5126
-3.5115
-3.5224
-3.5108
-3.4758
-3.4585
-3.4861
-3.5251
-3.5238
-3.4629
-3.5154
-3.5195
-3.523
-3.5099
-3.4785
-3.4479
-3.4854
-3.5324
-3.5129
Lat
54.9337
54.9335
54.9187
54.9155
54.9205
54.9183
54.9252
54.9388
54.9357
54.9365
54.9332
54.9315
54.9166
54.916
54.9208
54.916
54.9234
54.9366
54.9405
Number at age (number. m-2)
G
statistic
0
1
2
3
4
5
6
All
ages
Ages
2+
0.0318
0.0191
0.0141
0.0141
0.0141
0.0141
0.0141
0.0141
0.0141
0.0141
0.0127
0.0091
0.0085
0.0085
0.0085
0.0085
0.0085
0.0085
0.0085
2430
2260
0
0
920
710
100
1120
520
590
500
800
0
0
1280
200
50
10
460
30
20
0
0
10
30
0
0
50
70
20
60
0
0
20
0
20
20
10
0
0
0
0
10
10
30
0
10
0
0
0
0
10
0
0
10
20
10
0
0
0
0
10
0
0
0
0
0
0
0
0
0
10
0
20
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
10
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2460
2290
0
0
950
750
130
1120
580
660
520
860
0
10
1310
200
100
50
480
0
10
0
0
20
10
30
0
10
0
0
0
0
10
10
0
30
20
10
North Bank (West) continued
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
31
19
3
4
6
8
13
26
27
31
19
19
3
4
6
8
13
26
27
31
10
11
12
15
22
24
34
42
19
3
4
-3.4662
-3.5208
-3.5207
-3.5086
-3.4739
-3.4545
-3.4869
-3.5329
-3.5185
-3.4604
-3.5147
-3.5217
-3.5172
-3.5047
-3.485
-3.4567
-3.4946
-3.5345
-3.5226
-3.4622
-3.5314
-3.5191
-3.4991
-3.4653
-3.4772
-3.4479
-3.5356
-3.5345
-3.5187
-3.5232
-3.5043
54.9417
54.9309
54.9215
54.9158
54.9164
54.9169
54.9244
54.9392
54.9393
54.936
54.9322
54.9338
54.918
54.9181
54.92
54.9159
54.9272
54.9398
54.9371
54.9409
54.9282
54.9254
54.9265
54.926
54.9294
54.9352
54.9438
54.9499
54.9339
54.9214
54.9163
0.0085
0.0068
0.0057
0.0057
0.0057
0.0057
0.0057
0.0057
0.0057
0.0057
0.0053
0.0042
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.004
0.0035
0.0035
0.0035
0.0035
0.0035
0.0035
0.0035
0.0035
0.0035
0.003
0.003
40
890
0
0
140
210
70
0
1200
510
2790
600
0
0
50
230
30
0
70
170
0
450
0
2600
310
200
0
80
1270
20
0
0
50
0
0
30
10
10
40
50
40
40
20
0
0
60
20
10
20
10
30
30
10
20
30
30
10
0
110
80
10
0
0
10
0
10
0
20
10
0
0
10
10
0
0
0
0
30
0
30
10
0
10
10
10
10
0
0
0
0
0
0
0
0
0
0
0
0
0
0
10
0
0
0
0
0
0
0
0
10
0
0
0
0
0
0
0
0
0
0
0
20
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
10
0
0
0
0
0
20
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
40
950
0
10
170
240
90
50
1250
560
2840
620
0
0
110
280
50
60
90
200
40
470
30
2660
340
210
0
190
1370
30
0
0
10
0
10
0
20
10
10
0
10
10
0
0
0
0
30
10
40
10
0
10
10
10
30
0
0
0
0
20
0
0
TABLE 5
Results of adaptive surveys on a) Barnhourie and b) North Bank for 2007. Upper part of each
table shows abundance estimates, variance and standard error (SE) by age group derived from
Stage 1 of survey and from Stage 1 and 2 combined. Lower part of each table shows the same
calculations for biomass (tonnes). Table c) shows the overall results for the North Bank
(combined west and east).
a) Barnhourie
Abundance
Age
(millions)
0
1
2
3
4
5
6+
All ages
2+ ages
975.9
138.7
151.1
35.7
17.9
16.2
27.5
1363.0
248.4
18584.4
604.0
433.9
79.7
23.9
15.9
66.3
21727.7
848.3
SE
136.3
24.6
20.8
8.9
4.9
4.0
8.1
147.4
29.1
First and
Overall
Abundance
901.0
146.5
110.0
27.9
12.6
15.8
29.9
1243.6
196.2
second
Overall
Variance
18116.6
498.9
182.1
28.1
12.1
13.8
37.3
21320.8
365.6
combined
SE
134.6
22.3
13.5
5.3
3.5
3.7
6.1
146.0
19.1
First
Weight
288.4
550.4
1291.4
369.8
211.4
196.8
481.2
3389.3
2550.5
Stage
Variance
2518.5
8767.0
26863.6
8242.3
4069.7
2941.9
20502.5
137666.0
103347.0
SE
50.2
93.6
163.9
90.8
63.8
54.2
143.2
371.0
321.5
First and
Overall Weight
270.6
553.2
951.5
284.5
156.4
196.1
481.4
2893.8
2070.0
second
Overall
Variance
2458.7
5756.5
14892.3
2833.2
2027.5
2719.0
12477.1
70388.8
49878.2
combined
SE
49.6
75.9
122.0
53.2
45.0
52.1
111.7
265.3
223.3
First
Abundance
Stage
Variance
Weight
(tonnes)
b) North Bank (west)
Abundance
Age
(millions)
0
1
2
3
4
5
6+
All ages
2+ ages
8176.4
533.9
55.8
2.1
0.0
0.0
4.2
8772.4
62.1
787365.9
5003.1
207.9
4.2
0.0
0.0
8.5
827030.9
212.1
SE
887.3
70.7
14.4
2.1
0.0
0.0
2.9
909.4
14.6
First and
Overall Abundance
8567.2
520.9
53.9
7.9
4
0
2.4
9156.3
68.2
second
Overall Variance
688799.2
4407.4
62.2
9.1
10.3
0.0
1.9
710706.8
84.4
combined
SE
829.9
66.4
7.9
3.0
3.2
0.0
1.4
843.0
9.2
First
Weight
2889.3
2103.4
615.4
37.3
0.0
0.0
68.9
5714.3
721.6
Stage
Variance
100733.6
51860.2
24004.1
1391.4
0.0
0.0
2391.4
238228.9
26541.6
SE
317.4
227.7
154.9
37.3
0.0
0.0
48.9
488.1
162.9
First and
Overall Weight
3163.0
2013.0
613.9
129.3
46.8
0.0
40.6
6006.6
830.6
second
Overall Variance
100703.4
36828.5
8544.7
2478.8
1248.5
0.0
560.5
182095.5
12644.4
combined
SE
317.3
191.9
92.4
49.8
35.3
0.0
23.7
426.7
112.4
First
Abundance
Stage
Variance
Weight
(tonnes)
c) North Bank (combined west and east)
Abundance
(millions)
Age
0
1
2
3
4
5
6+
All ages
2+ ages
11661.8
632.2
78.7
20.3
4.0
0.0
2.4
12399.4
105.4
3213783.4
6700.8
368.0
162.0
10.3
0.0
1.9
3272996.9
543.1
SE
1792.7
81.9
19.2
12.7
3.2
0.0
1.4
1809.1
23.3
Combined
Overall Weight
4057.0
2375.1
875.6
335.7
46.8
0.0
40.6
7730.8
1298.7
West +
Overall Variance
294100.3
63880.5
46549.7
45077.6
1248.5
0.0
560.5
527934.9
93248.2
East
SE
542.3
252.7
215.8
212.3
35.3
0.0
23.7
726.6
305.4
Combined
Overall Abundance
West +
Overall Variance
East
TABLE 6
Abundance (No, millions) and density (No.m-2) of cockles on each ground during July / August
2007 shore survey. Figures given by age and overall. For comparison with previous surveys
North Bank east and west estimates have been combined.
Overall
Ages
Area
A
B
C
D
E
F
G
P
Total
0
1
2
3
4
5
6+
No
901.0
146.5
110.0
27.9
12.6
15.8
29.9
No / m2
28.9
4.7
3.5
0.9
0.4
0.5
1.0
No
11661.8
632.2
78.7
20.3
4.0
0.0
2.4
No / m2
177.8
9.6
1.2
0.3
0.1
0.0
0.0
No
630.0
72.2
4.4
3.7
3.0
3.8
19.9
No / m2
140.6
16.1
1.0
0.8
0.7
0.8
4.4
No
13.2
1.0
11.1
2.0
3.0
2.5
4.2
No / m2
3.8
0.3
3.2
0.6
0.9
0.7
1.2
No
1.3
2.1
5.7
1.2
2.0
0.0
0.7
No / m2
1.2
2.1
5.5
1.1
2.0
0.0
0.7
No
11.7
3.2
1.3
0.8
0.2
0.2
0.2
No / m2
17.7
4.9
2.0
1.2
0.3
0.3
0.3
No
33.7
1.7
2.4
4.0
0.0
0.0
3.0
No / m2
18.1
0.9
1.3
2.1
0.0
0.0
1.6
No
8.6
2.3
3.1
0.0
2.4
0.3
2.4
No / m2
1.6
0.4
0.6
0.0
0.4
0.1
0.4
A Barnhourie
B North Bank
C Carsethorn
D Auchencairn Bay
E Orchardton Bay
F Glenisle
G Rough Island
P Arbigland
Density
No/m ²
1243.6
39.8
12399.4
189.1
737.0
164.5
37.0
10.7
13.0
12.6
17.5
26.6
44.8
24.1
19.1
3.6
TABLE 7
Biomass (tonnes) and biomass per unit area (tonnes.km-2, tonnes) by age group and overall on
each ground surveyed in July / August 2007. For comparison with previous surveys North Bank
east and west estimates have been combined.
Overall
Ages
Area
A
B
C
D
E
F
G
P
Total
0
1
2
3
4
5
6+
Biomass
270.6
553.2
951.5
284.5
156.4
196.1
481.4
tonnes.km -2
8.7
17.7
30.5
9.1
5.0
6.3
15.4
Biomass
4057.0
2375.1
875.6
335.7
46.8
0.0
40.6
tonnes.km -2
61.9
36.2
13.4
5.1
0.7
0.0
0.6
Biomass
140.7
305.4
54.9
55.9
45.2
38.0
210.5
tonnes.km -2
31.4
68.2
12.3
12.5
10.1
8.5
47.0
Biomass
3.2
5.2
107.4
28.8
43.4
44.8
98.5
tonnes.km -2
0.9
1.5
31.1
8.3
12.6
13.0
28.5
Biomass
0.7
6.1
49.9
12.4
25.4
0.0
7.7
tonnes.km -2
0.6
5.9
48.4
12.0
24.6
0.0
7.4
Biomass
1.5
5.5
6.6
6.6
1.4
3.0
4.0
tonnes.km -2
2.3
8.3
9.9
10.0
2.1
4.6
6.1
Biomass
9.8
7.0
23.4
38.1
0.0
0.0
61.3
tonnes.km -2
5.3
3.7
12.6
20.5
0.0
0.0
32.9
Biomass
2.2
8.2
38.9
0.0
49.9
3.0
46.4
tonnes.km -2
0.4
1.6
7.4
0.0
9.4
0.6
8.8
A Barnhourie
B North Bank
C Carsethorn
D Auchencairn Bay
E Orchardton Bay
F Glenisle
G Rough Island
P Arbigland
Biomass
per Km-2
2893.8
92.7
7730.8
117.9
850.6
189.9
331.3
95.8
102.1
99.0
28.5
43.2
139.5
75.0
148.6
28.1
TABLE 8
Comparison of overall biomass estimates (tonnes), area surveyed (km2) and biomass per unit
area (t.km-2) for each ground in annual surveys, 1990 -2007.
1990
1991
1992
1993
Ground
tonnes
km ²
t.km-2
tonnes
km ²
t.km-2
tonnes
km ²
t.km-2
tonnes
km ²
t.km-2
A
5879
38.36
153.3
1028
25.04
41.0
1309
24.59
53.2
251
16.80
14.9
B
2427
15.28
158.8
1070
19.40
55.2
781
27.24
28.7
273
24.14
11.3
C
2105
2.22
948.2
2
2.22
0.9
0
0.79
0.4
D
214
0.58
369.0
22
0.58
37.9
103
0.58
177.8
11
0.70
15.9
E
146
0.36
405.6
6
0.36
16.7
53
0.36
147.0
4
0.36
11.3
F
47
0.29
162.1
66
0.39
169.2
122
0.49
248.8
59
0.49
120.1
G
55
0.27
207.7
23
0.27
85.2
341
0.27
1261.1
4
0.27
13.5
I
1822
7.16
254.5
850
5.74
148.1
1068
7.65
139.6
1496
8.84
169.3
18
0.02
1178.0
3794
61.99
61.2
2098
51.60
40.7
K
Total
A-K
12695
64.52
196.8
3067
1994
54.00
56.8
1995
1996
1997
Ground
tonnes
km ²
t.km-2
tonnes
km ²
t.km-2
tonnes
km ²
t.km-2
tonnes
km ²
t.km-2
A
498
29.21
17.1
264
33.07
8.0
531
30.65
17.3
1525
30.81
49.5
B
24
8.60
2.8
123
40.02
3.1
447
39.94
11.2
2249
59.88
37.6
D
203
0.58
349.8
37
1.11
33.7
392
2.14
182.8
304
1.99
153.4
E
61
0.36
169.5
34
0.84
40.3
112
1.08
103.5
52
0.96
54.6
F
38
0.49
77.3
58
0.49
119.2
-
-
-
1
0.49
1.4
G
240
0.34
706.3
283
0.31
924.2
86
0.31
280.8
108
0.31
354.5
I
847
7.41
114.3
1600
12.20
131.1
957
10.49
91.2
1741
11.68
149.1
K
17
0.02
1144.0
7
0.02
462.0
6
0.02
422.0
1
0.02
82.0
Total
A-K
1929
47.01
41.0
2406
88.06
27.3
2531
84.62
29.9
5983
106.12
82.0
England
N
-
-
-
91
12.08
7.6
319
13.62
23.4
238
12.99
18.3
O
-
-
-
25
1.90
13.3
53
2.38
22.5
138
2.89
47.6
Total
N+O
-
-
-
117
13.98
8.3
373
16
46
375
16
66
1998
1999
2000
2001
Ground
tonnes
km ²
t.km-2
tonnes
km ²
t.km-2
tonnes
km ²
t.km-2
tonnes
km ²
t.km-2
A
3010
30.97
97.2
3598
27.38
131.4
6065
31.95
189.8
3458
30.60
113.0
B
7442
53.22
139.8
5359
55.12
97
3853
65.51
58.8
206
62.40
3.3
D
625
1.83
342.3
1105
1.99
555
784
1.99
394.9
1258
3.00
419.2
E
249
1.08
230.4
307
0.96
320
62
0.84
73.8
93
0.96
97.1
G
17
0.31
55.2
205
0.31
661
105
0.31
343.1
159
0.31
520.2
I
2413
10.73
224.9
2383
10.73
222
2546
13.51
188.4
1293
12.46
103.8
K
0
0.02
0.0
-
-
-
-
-
-
-
-
-
Total
A-K
13756
98.15
140.2
12957
96.49
134.2
117.5
6467
109.73
58.94
13415 114.10
England
N
834
15.68
53.2
154
12.32
12.5
134
17.06
7.8
-
-
-
O
130
2.38
54.8
203
2.46
82.5
124
2.61
47.4
-
-
-
Total
N+O
965
18.06
53.4
357
14.80
24.2
258
19.67
13.1
-
-
-
2002
2003
2004
2005
Ground
tonnes
Km ²
t.km-2
tonnes
Km ²
t.km-2
tonnes
Km ²
t.km-2
tonnes
Km ²
t.km-2
A
3201.1
29.7
107.9
6941
30.0
231.1
7560.6
29.2
258.9
4493.4
30.9
145.4
B
7306.3
68.0
107.5
22650
70.5
321.5 21457.1
67.9
315.8 11366.8
69.9
162.6
D
651.4
3.2
203.6
844
3.1
275.7
391.7
3.1
126.4
424.7
3.2
132.7
E
158
1.5
108.8
148
0.9
169.2
115.2
0.9
128
249.8
1.1
227.1
F
204.1
0.5
449.6
251
0.5
551.8
234.2
0.5
468.4
407.3
0.9
519.3
G
549.2
1.3
417.9
711
2.0
347.2
243.9
2.0
122
229.1
2.0
114.6
I
2066.3
12.8
161.2
2381
11.6
205.2
3868.8
12.7
304.6
2133.4
12.0
177.8
14136.4 117.3
120.7
33926
118.5
286.2 33871.5 116.4
291.0 19304.5 119.7
161.3
Total
A-I
2006
2007
-2
t.km-2
Ground
tonnes
km ²
t.km
tonnes
A
2840.3
31.2
90.9
2893.8
31.2
92.7
B
2206.8
69.9
31.6
7730.8
65.6
117.9
850.6
4.5
189.9
405.4
3.2
126.9
331.3
3.5
95.8
E
61.6
1.1
58.3
102.1
1
99
F
439.2
0.8
558.8
28.5
0.7
43.2
G
107.5
2.2
48.7
139.5
1.9
75
I
2408.3
13
184.8
148.6
5.3
28.1
12225.2
113.7
107.5
C
D
P
km ²
Total
A-P
A
K
B
C
D
E
F
8469.1
Barnhourie
Balcary Bay
North Bank
Carsethorn
Auchencairn Bay
Orchardton Bay
Glenisle
121.4
69.8
I
G
P
Wigtown Bay
Rough Island
Arbigland
N
O
England
Cardurnock
Beckfoot
TABLE 9
Comparative summary of survey results for the Solway Firth, 1990-2007, showing
densities (a) and biomass (b) of under- ages and commercial- aged cockles. The minimum
commercial length is assumed (historically) to be 22 mm which is normally attained after one full
year in most parts of the Solway. Surveys from 1995 to 2000 include English grounds.
a) Densities of under aged cockles and Commercial-aged Cockles
Survey Year
Total survey Area (km2)
1990(Dec)
1991(Dec)
1992(Dec)
1993(May)*
1994(Apr)*
1995(Apr)*
1996 (Apr)*
1997(Apr)*
1998(Apr)*
1999(Apr)*
2000(May)*
2001(May)*
2002(April)*
2003(May)*
2004(May)*
2005(May)*
2006(April)*
2007(Aug)
64.52
54.00
61.99
51.63
47.01
102.03
100.62
121.77
116.21
111.28
133.77
109.73
117.16
118.52
116.4
119.73
Under-aged
15.36
26.11
47.69
9.82
1.43
4.96
15.23
21.28
11.64
20.35
7.19
4.64
127.49
5.87
11.0
5.70
Cockle density (No/m2)
Commercial
41.18
7.11
5.03
5.86
4.92
1.98
2.43
5.62
15.44
9.84
10.18
5.61
5.69
39.55
29.2
13.80
121.35
113.55
6.97
124.37
7.43
3.43
All ages
56.54
33.22
52.72
15.68
6.35
6.94
17.67
26.90
27.08
30.19
17.37
10.25
133.18
45.42
40.2
19.50
14.39
127.80
b) Biomass of under aged cockles and Commercial-aged Cockles
Survey year
1990
1991
1992
1993*
1994*
1995*
1996*
1997*
1998*
1999*
2000*
2001*
2002*
2003*
2004*
2005*
2006*
2007
Under-aged
8.8
10.4
29.3
3.8
0.9
3.2
10.9
10.4
12.1
17.4
7.9
4.3
70.2
7.4
11.7
5.9
Biomass (t/km ²)
Commercial
187.9
46.3
31.9
36.8
40.2
21.6
18.0
41.8
114.6
102.2
94.3
54.6
50.4
278.8
279.3
155.3
All ages
196.7
56.7
61.2
40.6
41.0
24.8
28.9
52.2
126.7
119.6
102.2
58.9
120.7
286.2
291.0
161.2
Under-aged
571
563
1815
196
41
323
1092
1263
1401
1940
1062
476
8228
876
1357
706
Biomass (tonnes)
Commercial
12123
2501
1979
1902
1888
2199
1811
5094
13318
11372
12610
5991
5908
33049
32515
18598
All ages
12694
3064
3794
2098
1929
2522
2903
6357
14721
13312
13672
6467
14136
33926
33872
19304
6.0
68.3
63.8
39.4
69.8
107.7
729
7751
7740
4474
8469
12225
*At the time of these surveys "under aged" cockles had one growth ring but had not reached commercial size, and
the "0" group of the year had not yet settled.
TABLE 10
a) Estimated available biomass (tonnes) available in July/August 2007 by area at hypothetical
minimum landing sizes (MLS) ranging from 25mm to 35mm, based on maximum stratum size. The
total biomass for each MLS is given which includes the biomass available at that size and above so, for
example, the biomass for an MLS of 30mm on Barnhourie would be 1,170 tonnes (not 4,513 tonnes).
MLS
mm.
25*
26
27
28
29
30*
31
32
33
34
35
Barnhourie
2079
1963
1826
1651
1356
1170
950
776
666
541
411
North Bank Auchencairn Orchardton
1805
1635
1444
1288
1146
1074
939
786
691
459
379
325
322
314
289
266
261
232
200
179
156
131
121
121
112
81
70
32
19
19
19
0
0
Glenisle
Rough Is.
Carsthorn
Arbigland
42
42
36
29
29
29
29
29
29
29
15
128
123
117
96
96
87
87
56
56
43
43
438
409
370
333
315
262
218
120
93
74
63
194
187
179
169
159
159
159
145
129
112
93
*The highlighted figures show the available biomass at the SSMA proposed lowest permissible MLS (25mm) and their
suggested initial precautionary MLS of 30mm
b) Indication of 22.5% and 30% of available biomass at 25mm and 30mm minimum landing sizes based
on table above.
Barnhourie
North Bank Auchencairn Orchardton
Glenisle
Rough Is.
Carsthorn
Arbigland
25mm Landing Size
Available
2079
1805
325
121
42
128
438
194
22.5%
468
406
73
27
9
29
99
44
30%
624
541
97
36
13
38
132
58
30mm Landing Size
Available
1170
1074
261
32
29
87
262
159
22.5%
263
242
59
7
7
20
59
36
30%
351
322
78
10
9
26
79
48
Figure 1. Chart of Solway Firth showing cockle grounds and 2007 station sampling positions on each ground.
55.0
B
A
B
C
D
E
F
G
I
P
54.9
I
Barhourie/Mersehead
North Bank (Top, E and W)
Carsethorn
Auchencairn Bay
Orchardton Bay
Glenisle
Rough Island
Wigtown Bay
Arbigland
C
P
A
D,E,F + G
54.8
54.7
-4.4
-4.3
-4.2
-4.1
-4.0
-3.9
-3.8
-3.7
-3.6
-3.5
-3.4
Figure 2a. Sampling stations on Barnhourie in 2007. Size of the triangles indicate abundance
of commercial sized 2+ cockles (Crosses show stations with zero 2+ cockles).
54.89
= 100.m-2
54.88
54.87
54.86
54.85
-3.76
-3.74
-3.72
-3.70
-3.68
-3.66
-3.64
-3.62
-3.60
Figure 2b. Shaded boxes indicate strata in which additional stations were allocated during stage
two. The large bold figures show the numbers of extra stations allocated to each stratum.
54.89
54.88
2
54.87
54.86
1
2
2
1
5
3
1
1
8
6
4
7
2
1
4
54.85
-3.76
-3.74
-3.72
-3.70
-3.68
-3.66
-3.64
-3.62
-3.60
Figure 2c. Sampling stations on North Bank 2007 is shown by distribution of all symbols. The size of the
triangles indicate abundance of 2+ cockles (Crosses show stations with zero 2+ cockles).
= 50.m
-2
54.97
54.96
54.95
54.94
54.93
54.92
54.91
-3.54
-3.52
-3.50
-3.48
-3.46
-3.44
-3.42
-3.40
-3.38
-3.36
-3.34
Figure 2d. Shaded boxes indicate strata in which additional stations were allocated during stage two.
The large bold figures show the numbers of extra stations allocated to each stratum.
54.97
54.96
54.95
1
1
54.94
4
54.93
4
4
8
1
1
1
1
5
5
4
1
1
54.92
4
4
54.91
-3.54
-3.52
-3.50
-3.48
-3.46
-3.44
-3.42
-3.40
-3.38
-3.36
-3.34
Figure 3a. Sampling stations for Auchencairn, Orchardton, Glenisle, and Rough Island in 2007 are shown by the
distribution of symbols. Size of triangles indicates abundance of 2+ cockles (Crosses show stations
with zero 2+ cockles). Strata are numbered separately for each sub area. Glenisle strata are indicated
by hatched area.
54.88
43
44
45
46
47 Rough
48Island 49
36
37
38
39
40
41
42
29
30
31
32
33
34
35
22
23
24
25
26
27
28
15
16
17
18
19
20
21
8
9
10
11
12
13
14
1
2
3
4
5
6
7
-2
=50.m
54.87
Glenisle
54.86
54.86
7
Orchardton
8
54.85
5
6
3
54.85
4
1
2
54.84
54.84
41
42
43
44
45
46
47
48
49
50
31
32
33
34
35
36
37
38
39
40
22
23
24
25
26
27
28
29
30
21
Auchencairn
54.84
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
8
9
10
54.83
-3.86
-3.85
-3.84
-3.83
-3.82
-3.81
-3.80
-3.79
Figure 3b. Sampling stations on Carsethorn in 2007 . Size of the triangles indicate abundance
of commercial sized 2+ cockles (Crosses show stations with zero 2+ cockles).
=50.m-2
54.95
54.94
54.93
-3.59
-3.58
-3.57
-3.56
-3.55
-3.54
Figure 3c. Sampling stations on Arbigland in 2007 . Size of the triangles indicate abundance
of commercial sized 2+ cockles (Crosses show stations with zero 2+ cockles).
54.92
-2
=50.m
54.91
54.90
54.89
54.88
-3.61
-3.60
-3.59
-3.58
-3.57
-3.56
-3.55
-3.54
Figure 4a. Contour map to show distribution of 2+ year old cockles at Barnhourie in 2007 based on two
stage adaptive survey results. Values are numbers.m-2
54.89
120
54.88
100
80
54.87
60
54.86
40
20
54.85
0
-3.76
-3.74
-3.72
-3.70
-3.68
-3.66
-3.64
-3.62
-3.60
Figure 4b. Contour map to show distribution of 0 and 1 year old cockles at Barnhourie in 2007 based
on two stage adaptive survey results. Values are numbers.m-2
54.89
800
750
700
54.88
650
600
550
500
54.87
450
400
350
300
54.86
250
200
150
100
54.85
50
0
-3.76
-3.74
-3.72
-3.70
-3.68
-3.66
-3.64
-3.62
-3.60
Figure 4c. Contour map to show distribution of 2+ year old cockles at North Bank in 2007, based
on survey results. Values are numbers.m-2
54.97
40
54.96
35
30
54.95
25
54.94
20
54.93
15
10
54.92
5
54.91
0
-3.54
-3.52
-3.50
-3.48
-3.46
-3.44
-3.42
-3.40
-3.38
-3.36
-3.34
Figure 4d. Contour map to show distribution of 0 and 1 year old cockles at North Bank in 2007, based
on survey results. Values are numbers.m-2 .
54.97
2600
2400
54.96
2200
2000
1800
54.95
1600
1400
54.94
1200
1000
54.93
800
600
54.92
400
200
54.91
0
-3.54
-3.52
-3.50
-3.48
-3.46
-3.44
-3.42
-3.40
-3.38
-3.36
-3.34
Figure 4e. Contour map to show distribution of 2+ year old cockles on Carsethorn in 2007
based on stratified random survey results. Values are numbers.m-2
130
120
110
54.95
100
90
80
70
60
54.93
50
40
30
20
54.92
10
0
-3.59
-3.58
-3.57
-3.56
-3.55
-3.54
Figure 4f. Contour map to show distribution of 0 and 1 year old cockles on Carsethorn in 2007
based on stratified random survey results. Values are numbers.m-2
1400
1300
1200
1100
54.95
1000
900
800
700
54.93
600
500
400
300
200
54.92
100
0
-3.59
-3.58
-3.57
-3.56
-3.55
-3.54
-2
Figure 5 Age compositon by Area. Numbers.m at each age
Barnhourie/Mersehead
North Bank
29
178
20
Numbers m2
Numbers m2
20.0
10.0
0.0
0
0
1
2
3
4
5
6+
0
1
2
Age
Auchencairn
Orchardton
4
5
6+
4
5
6+
4
5
6+
4
5
6+
Numbers m2
20.0
10.0
0.0
10.0
0.0
0
1
2
3
4
5
6+
0
1
2
Age
3
Age
Glenisle
Rough Island
20.0
20.0
Numbers m2
Numbers m2
3
Age
20.0
Numbers m2
10
10.0
0.0
10.0
0.0
0
1
2
3
4
5
6+
0
1
2
Age
3
Age
Arbigland
Carsthorn
141
20.0
Numbers m2
Numbers m2
20.0
10.0
0.0
10.0
0.0
0
1
2
3
Age
4
5
6+
0
1
2
3
Age
Figure 6 Biomass density estimates 1990 - 2007
1000
Barnhourie
750
tonnes/k-2
tonnes/k-2
1000
500
250
North Bank
750
500
250
0
0
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
1000
1000
Auchencairn
Orchardton
750
tonnes/k-2
tonnes/k-2
750
500
250
500
250
0
0
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
1000
1000
Glenisle
500
250
500
250
0
0
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
1000
Carsethorne
750
tonnes/k-2
Rough Island
750
tonnes/k-2
tonnes/k-2
750
1261
500
250
0
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Figure 7
140
Time series plot of table 9(a)
120
100
No/m
2
80
60
40
20
0
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Commercial
Under-aged
Time series plot of table 9(b)
300
250
Tonnes/Km2
200
150
100
50
0
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Commercial
Under-aged
APPENDIX 1
Historical abundance by age for each ground surveyed since 1990 showing numbers and
density.
Year
Area (km2)
A Barnhourie
1990
32.5
No.
-2
No.m
1991
25.0
No.
-2
No.m
1992
24.6
No.
-2
No.m
1993
16.8
No.
-2
No.m
1994
29.2
No.
-2
No.m
1995
33.1
No.
-2
No.m
1996
30.7
No.
-2
No.m
1997
30.8
No.
-2
No.m
1998
31.0
No.
-2
No.m
1999
27.4
No.
-2
No.m
2000
32.0
No.
-2
No.m
2001
30.6
No.
-2
No.m
2002
29.7
No.
-2
No.m
2003
30.0
No
No m ²
2004
29.2
No
No m ²
2005
30.9
No
No m ²
2006
31.2
No
No m ²
2007
31.23
No
No m ²
B North Bank
1990
15.3
1991
11.0
1992
9.6
1993
13.6
1994
1995
40.0
1996
39.9
1997
59.9
1998
53.2
1999
55.1
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
0
1
2
3
4
5
6+
Total
74.0
2.3
234.0
9.3
1040.0
42.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
901.0
28.9
950.0
29.2
35.7
1.4
43.7
1.8
125.9
7.5
18.0
0.6
51.0
1.5
401.6
13.1
440.0
14.3
229.2
7.4
871.8
31.8
182.5
5.7
240.4
7.9
1389.0
46.8
237.1
7.9
189.4
6.5
113.4
3.7
225.7
7.2
146.5
4.7
150.0
4.6
80.3
3.2
3.6
0.1
14.5
0.9
40.0
1.4
4.8
0.1
29.0
0.9
180.0
5.8
255.0
8.2
124.7
4.6
304.9
9.5
59.9
2.0
96.6
3.3
673.6
22.4
116.0
4.0
82.8
2.7
56.8
1.8
110.0
3.5
52.0
1.6
15.5
0.6
24.2
1.0
4.8
0.3
0.0
0.0
9.5
0.3
7.9
0.3
1.6
0.1
92.5
3.0
120.5
4.4
84.5
2.6
143.3
4.7
29.5
1.0
58.7
2.0
448.4
15.4
40.1
1.3
48.2
1.5
27.9
0.9
69.0
2.1
2.8
0.1
2.1
0.1
8.2
0.5
0.0
0.0
0.0
0.0
1.6
0.1
3.2
0.1
20.0
0.6
55.4
2.0
117.3
3.7
44.1
1.4
65.2
2.2
24
0.8
122.1
4.2
236.3
7.6
22.1
0.7
12.6
0.4
13.0
0.4
1.2
0.1
0.5
0.0
0.5
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
2.8
0.1
13.7
0.5
87.6
2.7
21.9
0.7
26.7
0.9
23.9
0.8
41.3
1.4
26.1
0.8
102.5
3.3
15.8
0.5
0.3
0.0
0.3
0.0
0.3
0.0
1.5
0.1
1.6
0.0
0.0
0.0
1.6
0.1
1.6
0.1
2.9
0.1
21.1
0.7
11.8
0.4
9.8
0.3
46.4
1.5
18.9
0.6
4.7
0.2
23.1
0.7
29.9
1.0
1308.0
40.2
369.8
14.8
1114.3
45.3
154.2
9.2
47.5
1.6
66.9
2.0
440.1
14.4
626.4
20.3
601.1
19.4
1189.0
43.4
797.9
25.0
521.4
17.0
1616.8
54.4
1063.7
35.4
936.1
32.1
503.4
16.3
478.5
15.3
1243.6
39.8
39.2
2.6
800.0
72.8
434.3
45.4
0.0
0.0
393.3
25.7
14.0
1.3
32.3
3.4
163.6
12.0
8.8
0.6
55.2
5.0
2.7
0.3
9.0
0.7
3.2
0.2
5.9
0.5
14.8
1.5
4.3
0.3
3.6
0.2
0.6
0.1
0.8
0.1
7.6
0.6
0.4
0.0
0.5
0.0
0.1
0.0
0.5
0.0
0.1
0.0
0.2
0.0
0.1
0.0
0.1
0.0
448.7
29.4
876.3
79.7
485.0
50.7
185.1
13.6
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
199.0
5.0
228.3
5.7
1300.0
21.7
680.0
12.8
430.0
0.0
0.0
41.2
1.0
120.0
2.0
590.0
11.1
110.0
0.0
0.0
3.2
0.1
35.0
0.6
79.0
1.5
230.0
0.0
0.0
0.0
0.0
0.0
0.0
16.0
0.3
25.0
0.0
0.0
0.0
0.0
0.0
0.0
6.3
0.1
3.2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
199.0
5.0
272.7
6.8
1455.0
24.3
1371.3
25.8
798.2
i
-2
2000
65.5
2001
62.4
2002
68.0
2003
70.5
2004
68.0
2005
69.9
2006
69.8
2007
65.6
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No
No m ²
No
No m ²
No
No m ²
No
No m ²
No
No m ²
D Auchencairn
1990
0.6
No.
-2
No.m
1991
0.6
No.
-2
No.m
1992
0.6
No.
-2
No.m
1993
0.7
No.
-2
No.m
1994
0.6
No.
-2
No.m
1995
1.1
No.
-2
No.m
1996
2.1
No.
-2
No.m
1997
2.0
No.
-2
No.m
1998
1.8
No.
-2
No.m
1999
2.0
No.
-2
No.m
2000
2.0
No.
-2
No.m
2001
3.0
No.
-2
No.m
2002
3.2
No.
-2
No.m
2003
3.1
No
No m ²
2004
3.1
No
No m ²
2005
3.2
No
No m ²
2006
3.2
No
No m ²
2007
3.5
No
No m ²
E Orchardton
1990
0.4
1991
0.4
1992
0.4
1993
0.4
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
11661.8
177.9
7.8
371.0
5.7
182.8
2.9
12270.3
180.4
316.4
4.5
858.4
12.6
167.3
2.4
411.2
5.9
632.2
9.6
2.0
69.7
1.1
3.2
0.1
77.5
1.1
3159.5
44.8
181.3
2.7
81.0
1.2
41.3
0.6
78.7
1.2
4.2
62.0
0.9
1.6
0.0
3.1
0.0
77
1.1
1628.8
24.0
166.6
2.4
10.6
0.2
20.3
0.3
0.5
49.5
0.8
0.0
0.0
0.0
0.0
4
0.1
110.9
1.6
590.6
8.4
6.7
0.1
4.0
0.1
0.1
34.1
0.5
0.0
0.0
3.1
0.0
0.9
0.0
12.1
0.2
22.7
0.3
61.9
0.9
0.0
0.0
0.0
12.4
0.2
0.0
0.0
3.1
0.0
0
0.0
2.1
0.0
4.7
0.1
19.5
0.3
2.4
0.0
14.5
598.7
9.1
187.6
3.0
12357.1
181.7
3557.8
50.5
2793.6
41.1
1032.9
14.8
551.2
7.9
12399.4
120.5
12.0
20.7
5.3
9.1
61.6
106.2
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
13.2
3.8
33.4
57.6
0.4
0.6
3.3
5.8
3.0
4.3
3.5
6.0
18.0
16.2
50.0
23.4
44.0
22.1
7.1
3.9
200.0
100.5
12.0
6.0
32.0
10.7
15.5
4.8
11.4
3.7
11.5
3.7
0.5
0.2
38.5
12.1
1.0
0.3
2.2
3.8
1.1
1.9
0.2
0.3
0.2
0.3
9.3
16.0
0.0
0.0
14.0
6.5
25.0
12.6
56.0
30.6
15.0
7.5
88.0
44.2
16.0
5.3
16.5
5.2
11.4
3.7
4.0
1.3
26.1
8.2
7.6
2.4
11.1
3.2
1.8
3.1
0.1
0.2
0.7
1.1
0.1
0.1
2.3
4.0
0.0
0.0
3.2
1.5
8.7
4.4
17.0
9.3
32.0
16.1
16.0
8.0
83.0
27.7
8.5
2.7
4.3
1.4
6.8
2.2
2.9
0.9
7.8
2.4
2.0
0.6
11.0
19.0
0.1
0.2
0.2
0.4
0.3
0.4
0.0
0.0
0.0
0.0
10.0
4.7
1.6
0.8
13.0
7.1
18.0
9.0
4.0
2.0
9.0
3.0
31.5
9.8
2.9
0.9
6.1
2.0
4.1
1.3
1.0
0.3
3.0
0.9
1.1
1.9
0.7
1.2
0.4
0.6
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.6
0.8
3.2
1.7
1.0
0.5
4.8
2.4
9.5
3.2
1.5
0.5
4.1
1.3
1.0
0.3
2.1
0.7
5.8
1.8
2.5
0.7
0.1
0.1
0.3
0.5
0.0
0.1
4.6
7.9
0.0
0.0
0.0
0.0
1.6
0.8
3.2
1.7
1.6
0.8
1.6
0.8
2.5
0.8
0.5
0.2
29.4
9.6
9.5
3.1
9.2
2.9
6.4
2.0
4.2
1.2
61.5
106.0
7.8
13.4
66.6
114.9
3.7
5.3
19.7
34.0
18.0
16.2
77.2
36.1
82.5
41.4
99.5
54.4
267.6
134.5
126.4
63.5
152.0
50.7
74.0
23.1
63.6
20.8
38.9
12.6
45.0
14.1
67.1
21.0
37.0
10.7
5.7
15.8
4.5
12.4
33.6
93.3
0.0
0.0
27.5
76.4
0.1
0.2
1.8
5.1
0.9
2.4
1.7
4.8
0.2
0.6
0.3
0.7
0.1
0.3
0.3
0.9
0.0
0.0
0.9
2.5
0.0
0.1
4.0
11.1
0.1
0.3
0.0
0.1
0.1
0.2
0.0
0.0
ii
0.0
0.1
0.2
0.1
0.4
0.0
0.1
0.4
0.0
0.1
39.3
109.3
4.8
13.3
36.8
102.3
1.2
3.3
1994
0.4
1995
0.8
1996
1.1
1997
1.0
1998
1.1
1999
1.0
2000
0.8
2001
1.0
2002
1.1
2003
0.9
2004
0.9
2005
1.1
2006
1.1
2007
1.03
F Glen Isle
1990
0.3
1991
0.4
1992
0.5
1993
0.5
1994
0.5
1995
0.5
1996
1997
0.5
1998
1999
2000
2001
2002
0.5
2003
0.5
2004
0.5
2005
0.6
2006
0.8
2007
0.66
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No
No m ²
No
No m ²
No
No m ²
No
No m ²
No
No m ²
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.3
1.2
0.0
0.0
3.6
4.3
14.0
13.0
19.0
19.8
6.0
5.6
40.0
41.7
1.2
1.4
8.4
8.8
22.7
19.9
0
0.0
1.2
1.3
17.1
15.6
4.3
4.1
2.1
2.1
2.4
6.7
2.4
2.9
2.4
2.2
2.4
2.5
31.0
28.7
6.0
6.3
4.8
5.7
1.2
1.3
4.0
3.5
1.2
1.4
9.7
10.8
5.2
4.7
2.5
2.3
5.7
5.5
1.2
3.3
0.0
0.0
1.2
1.1
2.4
2.5
9.6
8.9
9.6
10.0
1.2
1.4
7.2
7.5
5.3
4.6
6
6.9
1.2
1.3
1.9
1.8
1.4
1.4
1.2
1.1
0.0
0.0
1.2
1.4
2.4
2.2
0.0
0.0
9.6
8.9
6.0
6.3
1.2
1.4
1.2
1.3
5.8
5.1
0
0.0
2.4
2.7
5.0
4.6
0.5
0.5
2.0
2.0
0.0
0.0
0.0
0.0
1.2
1.1
0.0
0.0
0.0
0.0
2.4
2.5
0.0
0.0
0.0
0.0
2.5
2.2
0
0.0
0.0
0.0
3.6
3.3
1.3
1.2
0.0
0.0
1.2
3.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
0.9
2.4
2.7
0.7
0.8
4.2
3.8
1.2
1.1
0.7
0.7
4.8
13.3
7.2
8.6
21.2
19.6
23.8
24.8
56.2
52.0
64.0
66.7
8.4
10.0
18.0
18.8
41.4
36.3
9.6
11.0
15.2
16.9
37.1
33.7
11.2
10.6
13.0
12.6
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No
No m ²
No
No m ²
No
No m ²
No
No m ²
No
6.0
20.7
3.2
8.2
6.4
13.1
0.0
0.0
0.0
0.0
0.0
0.0
9.4
32.6
0.5
1.2
4.3
8.8
6.0
12.3
0.0
0.0
0.0
0.0
1.1
3.7
0.6
1.6
2.5
5.1
5.9
12.0
0.0
0.0
1.0
2.0
0.3
1.0
0.1
0.1
7.2
14.7
1.9
3.8
0.0
0.0
0.0
0.0
0.3
1.1
0.0
0.0
1.3
2.7
1.9
3.8
1.0
2.0
1.0
2.0
0.0
0.1
0.0
0.1
0.5
1.0
0.6
1.3
0.0
0.0
1.0
2.0
0.0
0.0
0.0
0.4
0.8
0.5
0.9
1.0
2.0
0.0
0.0
17.1
59.0
4.4
11.3
22.6
46.2
16.7
34.1
1.9
4.0
2.9
5.9
0.0
0.0
2.9
5.9
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
2.9
5.9
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
11.7
5.7
12.6
22.7
50.0
1.1
2.2
3.4
5.5
12.2
15.6
3.2
1.1
2.4
19.3
42.5
8.0
16
0.0
0.0
2.7
3.4
1.3
0.0
0.0
2.2
4.8
11.4
22.8
19.3
31.1
1.3
1.7
0.8
1.1
2.4
1.1
2.4
1.1
2.2
13.8
22.3
3.9
4.9
0.2
4.5
9.9
2.3
5.1
2.3
4.6
6.8
11.0
6.4
8.2
0.2
19.3
42.5
7.9
17.4
2.2
4.4
5.3
8.5
25.0
31.8
0.2
31.7
69.8
55.5
122.2
26.1
52.2
48.6
78.4
51.6
65.6
17.5
iii
No m ²
17.7
4.9
2.0
1.2
0.3
0.3
0.3
26.6
G Rough Island
1990
0.3
No.
-2
No.m
1991
0.3
No.
-2
No.m
1992
0.3
No.
-2
No.m
1993
0.3
No.
-2
No.m
1994
0.3
No.
-2
No.m
1995
0.3
No.
-2
No.m
1996
0.3
No.
-2
No.m
1997
0.3
No.
-2
No.m
1998
0.3
No.
-2
No.m
1999
0.3
No.
-2
No.m
2000
0.3
No.
-2
No.m
2001
0.3
No.
-2
No.m
2002
1.3
No.
-2
No.m
2003
2.0
No
No m ²
2004
2.0
No
No m ²
2005
2.0
No
No m ²
2006
2.2
No
No m ²
2007
1.9
No
No m ²
5.6
20.7
5.5
20.4
262.4
971.9
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
33.7
18.1
13.4
49.4
0.7
2.5
10.6
39.4
3.5
13.0
2.4
6.9
6.1
19.7
11.0
35.5
32.0
103.2
0.0
0.0
21.0
67.7
0.0
0.0
0.0
0.0
55.2
42.0
22.4
10.9
16.3
8.2
8.9
4.4
5.8
2.6
1.7
0.9
2.1
7.6
1.4
5.3
1.2
4.3
0.1
0.3
23.1
67.9
3.6
11.6
1.5
4.8
10.0
32.3
4.1
13.2
1.5
4.8
1.0
3.2
0.5
1.6
15.8
12.0
25.6
12.5
14.1
7.0
1.1
0.5
4.5
2.0
2.4
1.3
0.1
0.4
0.2
0.7
2.9
10.6
0.0
0.1
7.4
21.8
15.0
48.4
3.1
10.0
1.5
4.8
0.0
0.0
19.0
61.3
1.5
4.8
4.1
13.4
3.0
2.3
6.8
3.3
15.4
7.7
8.7
4.3
1.9
0.9
4.0
2.1
0.8
2.8
0.1
0.2
0.4
1.5
0.0
0.1
2.0
5.9
6.1
19.7
2.0
6.5
0.5
1.6
0.0
0.0
2.0
6.5
3.6
11.6
2.0
6.5
13.3
10.1
2
1.0
1.7
0.8
4.3
2.1
1.0
0.4
0.0
0.0
0.2
0.6
0.1
0.4
0.1
0.4
0.0
0.0
0.0
0.0
0.5
1.6
0.5
1.6
0.5
1.6
0.0
0.0
0.5
1.6
2.6
8.4
9.2
30.1
16.1
12.3
8.4
4.1
0.0
0.0
5.7
2.8
1.0
0.4
0.0
0.0
5.8
21.5
0.0
0.0
0.1
0.5
0.0
0.0
1.3
3.9
0.0
0.0
0.0
0.0
0.5
1.6
0.0
0.0
0.0
0.0
2.0
6.5
0.0
0.0
14.2
10.8
31.3
15.3
2.3
1.2
1.1
0.5
0.7
0.3
3.0
1.6
27.8
103.1
8.0
29.6
277.7
1028.6
3.6
13.5
36.2
106.4
31.3
101.0
18.1
58.4
45.0
145.3
4.1
13.2
44.0
142.0
10.7
34.6
15.8
51.7
117.5
89.4
96.5
47.1
49.8
24.9
29.7
14.7
14.9
6.8
44.8
24.1
736.0
102.8
352.0
61.3
976.0
151.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
216.0
30.2
76.8
13.4
27.6
4.3
167.8
21.9
22.0
3.0
94.3
7.7
430.0
41.0
510.0
43.7
120.0
11.2
570.0
53.1
337.1
24.9
45.4
3.6
94.0
13.1
47.2
8.2
25.8
4.0
21.6
2.8
81.0
10.9
32.2
2.6
33.0
3.1
170.0
14.6
360.0
33.6
64.0
6.0
237.9
17.6
94.2
7.5
4.0
0.6
29.0
5.1
31.9
4.9
40.7
5.3
9.6
1.3
57.4
4.7
12.0
1.1
45.0
3.9
62.0
5.8
130.0
12.1
21.3
1.6
54.8
4.4
7.0
1.0
2.6
0.5
14.7
2.3
81.5
10.7
14.0
1.9
12.0
1.0
21.0
2.0
12.0
1.0
4.8
0.4
62.0
5.8
74.1
5.5
9.6
0.8
7.0
1.0
0.9
0.2
1.4
0.2
64.8
8.5
7.2
1.0
29.0
2.4
0.0
0.0
12.0
1.0
9.5
0.9
12.0
1.1
22.3
1.6
18.8
1.5
3.0
0.4
2.1
0.4
29.8
4.6
3.9
0.5
16.4
2.2
17.0
1.4
9.6
0.9
9.6
0.8
12.0
1.1
0.0
0.0
9.5
0.7
6.7
0.5
1067.0
149.0
510.6
89.0
1107.1
171.6
380.3
49.7
150.2
20.3
241.9
19.8
505.6
48.2
758.6
64.9
568.3
53.0
838.0
78.1
702.2
51.9
229.5
18.4
I Wigtown
1990
7.2
1991
5.7
1992
6.5
1993
7.7
1994
7.4
1995
12.2
1996
10.5
1997
11.7
1998
10.7
1999
10.7
2000
13.5
2001
12.5
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
No.
-2
No.m
iv
2002
12.8
2003
11.6
2004
12.7
2005
12.0
2006
No.
-2
No.m
No
No m ²
No
No m ²
No
No m ²
No
No m ²
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1177.5
92.0
85.3
7.3
205.7
16.2
370.9
31.0
147.5
11.3
25.9
2.0
355.7
30.6
92.7
7.3
71.0
5.9
238.9
18.3
2007
v
69.3
5.4
26.7
2.3
392.1
30.9
34.7
2.9
68.1
5.2
52.7
4.1
31
2.7
81.7
6.4
101.3
8.5
22.8
1.7
8.9
0.7
19.7
1.7
20.2
1.6
33.5
2.8
55.9
4.3
30.1
2.4
18.2
1.6
33.5
2.6
30.1
2.5
38.9
3.0
1364.4
106.6
536.5
46.2
825.9
65.0
641.6
53.6
572.0
43.9
APPENDIX 2
Historical biomass by age for each ground surveyed since 1990
Year
Area
(km2)
A Barnhourie
1990
32.52
1991
25.04
1992
24.59
1993
16.84
1994
29.21
1995
33.07
1996
30.65
1997
30.81
1998
30.97
1999
27.38
2000
31.95
2001
30.6
2002
29.7
2003
30.0
2004
29.2
2005
30.9
2006
31.2
2007
31.23
0
1
2
3
4
5
6+
Total
71.7
107.5
755.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
270.6
3521.3
102.8
247.5
66.3
13.6
42.3
291.6
192.2
244.7
748.1
362.4
236.6
808.7
322.4
200.7
159.4
197.3
553.2
788.0
622.9
22.7
54.3
451.4
25.5
160.9
1225.6
1501.7
748.2
2145.6
471.0
564.4
4461.8
577.9
397.1
286.0
951.5
481.0
127.0
237.4
37.0
0.0
157.1
71.4
11.7
887.8
1123.5
906.0
1698.1
384.3
645.8
4178.1
383.1
389.6
284.5
854.9
37.4
30.4
79.3
0.0
0.0
7.2
67.7
289.5
711.0
1229.7
571.3
867.0
304.6
1597.8
2977.2
228.1
156.4
162.1
21.8
7.6
8.1
0.0
0.0
0.0
0.0
58.4
224.1
1150.2
300.3
416.5
399.3
640.3
499.4
1358.9
196.1
7.2
0.3
6.1
33.4
38.7
0.0
27.9
27.9
42.5
271.3
181.0
160.2
806.7
365.8
77.2
380.4
481.4
5879.0
1026.5
1301.2
251.1
498.5
263.6
531.1
1525.0
3010.0
3597.4
6065.2
3458.3
3201.1
6940.6
7560.6
4493.4
2840.3
2070.0
B North Bank
1990
15.28
1991
10.99
1992
9.56
1993
13.62
1994
1995
40.02
1996
39.94
1997
59.88
1998
53.22
1999
55.12
2000
65.51
2001
62.4
2002
68.0
2003
70.5
2004
68.0
2005
69.9
2006
69.8
2007
65.6
19.0
327.7
270.6
0.0
2235.0
92.4
210.0
67.2
64.5
565.5
37.4
59.3
40.8
67.3
243.2
43.4
57.1
8.6
15.6
93.8
8.3
7.7
1.4
7.4
2.6
0.3
2.4
1.9
2427.2
1069.5
780.6
273.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
3163.0
123.4
207.4
776.0
807.7
445.1
397.8
144.5
6753.0
344.9
936.5
239.8
363.2
2013.0
0.0
205.8
995.3
5157.8
955.7
633.0
27.7
419.3
21453.5
1106.8
582.5
315.2
613.9
0.0
33.9
477.9
1148.8
3428.1
951.6
33.7
31.3
814.5
17646.4
1922.5
172.1
129.3
0.0
0.0
0.0
211.4
469.7
856.3
0.0
0.0
30.1
1517.2
8129.6
100.1
46.8
0.0
0.0
0.0
116.5
60.4
738.0
0.0
49.2
7.4
197.9
399.4
958.6
0.0
0.0
0.0
0.0
0.0
0.0
276.3
0.0
53.5
0
52.3
93.0
297.6
40.6
123.4
447.0
2249.1
7442.3
5358.9
3853.0
206.0
7306.3
22650.4
21457.1
11366.8
2206.8
830.6
D Auchencairn
1990
0.58
1991
0.58
1992
0.58
1993
0.7
1994
0.58
1995
1.11
1996
2.14
1997
1.99
1998
1.83
1999
1.99
2000
1.99
2001
3
2002
3.2
2003
3.1
2004
3.1
10.4
5.0
77.9
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
118.2
1.7
11.0
4.5
2.0
37.5
41.9
19.2
9.6
276.1
13.8
30.8
13.4
31.4
22.7
8.7
7.6
1.2
1.3
88.4
0.0
108.1
124.3
235.9
94.8
521.5
87.9
75.1
97.1
22.0
9.5
0.9
5.9
0.8
28.8
0.0
37.0
84.8
129.9
332.9
114.2
875.3
91.3
49.9
73.6
61.8
1.1
1.7
3.6
0.0
0.0
204.9
27.1
144.9
209.9
39.7
107.5
436.8
33.9
85.4
5.4
5.2
2.8
0.3
0.0
0.0
0.0
24.6
43.9
163.6
70.9
115.2
28.6
69.5
17.5
0.6
2.5
0.6
83.6
0.0
0.0
24.6
60.8
28.1
23.5
41.0
6.2
561.9
170.5
214.0
22.0
103.1
11.0
202.9
37.5
391.9
304.4
625.1
1105.4
784.0
1258.0
651.4
843.6
391.7
vi
2005
3.2
2006
3.2
2007
3.5
E Orchardton
1990
0.36
1991
0.36
1992
0.36
1993
0.36
1994
0.36
1995
0.84
1996
1.08
1997
0.96
1998
1.08
1999
0.96
2000
0.84
2001
0.96
2002
1.14
2003
0.873
2004
0.9
2005
1.1
2006
1.1
2007
1.03
0.0
0.0
3.2
1.3
43.6
5.2
99.2
52.7
107.4
30.7
80.9
28.8
60.1
13.4
43.4
31.3
88.6
44.8
202.2
126.3
98.5
424.7
405.4
322.9
4.1
3.2
27.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.7
95.4
0.4
8.2
1.2
0.0
5.4
11.3
18.5
2.7
42.6
0.2
3.9
9.7
0
0.3
16.0
4.5
6.1
10.0
2.2
2.6
0.4
20.8
21.1
22.9
13.1
104.5
31.0
35.5
6.2
6.5
9.9
54.0
18.7
8.4
49.9
2.7
0.1
11.1
0.4
11.6
0.0
17.2
20.8
80.5
98.5
8.8
68.4
23.0
85.6
12.8
23.0
8.8
12.4
32.3
-
1.0
1.6
0.0
7.3
51.1
0.0
61.1
86.3
17.7
14.8
59.5
0
36.5
59.6
3.8
25.4
1.1
0.4
0.9
0.1
0.0
0.0
9.3
0.0
0.0
48.2
0.0
0.0
16.9
0
0.0
37.7
13.3
0.0
1.9
0.4
28.7
0.0
0.0
0.0
0.0
0.0
0.0
0.0
42.3
52.2
11.6
94.8
22.9
7.7
145.5
6.3
52.9
4.1
61.0
33.9
111.8
52.5
248.9
306.5
62.0
93.0
158.0
147.7
115.2
249.8
61.6
95.4
9.0
3.8
4.5
0.0
0.0
0.0
27.7
6.3
16.3
2.8
0.0
0.0
5.7
34.6
18.9
17.0
0.0
16.7
1.8
10.3
59.9
11.7
0.0
0.0
2.4
5.5
12.6
15.3
18.2
19.7
0.2
5.0
5.5
6.6
0.0
21.4
0.0
0.0
4.2
5.4
19.7
0.0
46.8
65.6
121.9
58.9
37.9
57.8
F Glen Isle
1990
0.29
1991
0.39
1992
0.49
1993
0.49
1994
0.49
1995
0.49
1996
1997
0.49
1998
1999
2000
2001
2002
0.45
2003
0.454
2004
0.454
2005
0.62
2006
0.79
2007
0.66
0.0
0.7
0.0
0.0
0.0
0.0
0.0
0.7
0.0
0.0
0.0
0.0
0.0
1.5
5.5
22
0.4
4.0
6.5
5.5
2.4
73.9
35.5
0.0
8.8
6.6
0.0
18.9
100.6
151.7
7.1
6.6
7.4
5.8
16.3
118.5
31.9
1.4
30.9
17.8
39.4
68.4
62.9
3.0
157.9
112.1
42.0
64.7
322.0
4.0
204.1
250.5
234.2
407.3
439.2
21.5
G Rough Island
1990
0.27
1991
0.27
1992
0.27
1993
0.27
1994
0.34
1995
0.31
1996
0.31
1997
0.31
1998
0.31
1999
0.31
2000
0.31
2001
0.31
2002
1.31
2003
2.0
2004
2.0
2005
2.0
2006
2.2
2007
1.9
3.6
2.7
247.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
9.8
36.1
3.8
48.1
2.6
2.9
7.2
7.6
14.1
0.0
17.8
0.0
0.0
34.4
38.6
12.6
16.4
8.0
7.0
7.7
12.6
10.6
0.4
160.5
30.1
5.6
52.0
16.9
9.1
5.9
1.3
50.9
110
62.1
5.2
26.7
23.4
0.8
1.7
28.2
0.2
47.9
169.5
37.1
16.6
0.0
143.6
14.1
31.7
23.5
58.3
121.9
74.8
24.0
38.1
5.3
0.6
4.1
0.3
16.3
68.7
28.4
9.7
0.0
26.1
31.2
17.3
109.9
21.2
28.0
62.0
14.2
0.0
1.2
1.3
1.2
0.0
0.0
7.3
7.3
9.7
0.0
8.0
29.8
108.9
161.9
57.9
0.0
54.9
25.2
0.0
0.0
1.4
0.0
12.5
0.0
0.0
6.3
0.0
0.0
23.6
0.0
168.6
425.5
19.3
15.9
9.4
61.3
54.7
22.7
340.5
3.6
240.1
282.8
85.9
108.5
16.9
204.6
105.0
159.0
549.2
711.5
243.9
229.1
107.5
122.8
vii
I Wigtown
1990
7.16
1991
5.74
1992
6.45
1993
7.65
1994
7.41
1995
12.2
1996
10.49
1997
11.68
1998
10.73
1999
10.73
2000
13.53
2001
12.5
2002
12.8
2003
11.607
2004
12.7
2005
12.0
2006
13.0
2007
272.0
112.8
424.8
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
788.0
240.9
86.8
51.0
12.4
52.3
333.8
134.0
110.9
309.1
223.3
60.1
603.7
117.1
183.3
269.2
106.2
527.0
242.4
157.6
72.2
358.2
219.2
181.6
839.1
1370.1
288.6
1028.4
470.9
96.7
1404.3
338.4
258.4
909.5
36.0
187.8
245.2
228.7
73.4
581.1
117.8
318.4
564.6
899.2
150.7
439.9
526.2
184.4
2152.4
181.3
363.3
viii
81.0
23.4
129.3
613.3
124.2
136.7
201.7
98.8
50.9
709.4
680.4
83.9
458.0
262.4
619.3
811.6
166.6
81.0
11.7
14.6
488.0
63.5
419.4
0.0
207.2
116.4
176.4
303.0
167.6
69.9
207.2
179.2
309.7
479.2
37.0
30.8
9.4
43.1
215.2
190.9
121.8
143.8
200.2
0.0
159.7
70.5
311.8
205.8
396.2
303.2
383.5
1822.0
849.8
1067.6
1496.4
846.8
1599.6
956.7
1741.3
2413.1
2382.7
2546.0
1293.0
2066.3
2381.3
3868.8
2133.4
2408.3
APPENDIX 3
Other Bivalve Species
General
During the FRS 2007 Solway survey all bivalves were retained from each cockle quadrat
sample at each sampling station. For that reason the distribution of the 732 stations, shown
in Figure 1 of the main report, applies equally to the bivalve samples. This also applies to
the two adaptive surveys but it should be noted that the second stages were targeted on the
basis of first stage cockle distribution, and not on the distribution of other bivalve species.
The samples were taken using a 0.1 m2 quadrat frame, from which sediment was removed
to a depth of up to 100 mm and passed through a 5 mm mesh sieve. All bivalves were kept
for analysis. The cockles were later removed from each sample, to be assessed separately,
and the remaining bivalves weighed and measured but no attempt was made to age them.
Apart from cockles eight species were found: Thin tellin, Angulus tenuis (da Costa); Banded
wedge shell, Donax vittatus (da Costa); Bean-like tellins, Fabulina fibula (Gmelin); Macoma,
Macoma balthica (L); Sand gaper, Mya arenaria (L); Common mussel, Mytilus edulis (L);
Peppery furrow shell, Scrobicularia plana (da Costa); and Spisula subtruncata (da Costa).
By far the most abundant and widespread other bivalve species was macoma (also know as
the Baltic tellin), which accounted for 92% of the abundance of other bivalve species.
Mussels, found on two of the grounds, accounted for 6%, the thin tellin 1% and the
remaining species accounted for 1% in total.
Of the 732 sample stations other bivalves were recorded at 447 and of these macoma were
present at 430. A total of 6918 macoma were found in the survey samples. From these the
abundance and biomass of macoma was calculated along with the occurrence of the other
far less numerous species. The overall abundance estimate for macoma was 15479
millions, with a biomass of 7245 tonnes. Further details of macoma and the other species
on the different grounds can be found in the following sections
Barnhourie Bank (A)
The survey of Barnhourie Bank was undertaken using the 2 stage adaptive technique. A
total of 246 stations, including both stages of the survey, were sampled overall (Figure 1 of
the main report) of which 128 contained macoma. The maximum size of each of the
98 strata was 0.326 km2 and the total survey area was 31.23km2. Spacing between the
stations was variable depending on the randomisation process and the addition of stations to
some strata in Stage 2 of the adaptive process. The samples yielded 961 macoma from the
128 stations including both stages - an average of 7.5 per station. The macoma abundance
estimate, after the inclusion of the stage 2 samples was 942.7 +/- 172.1 millions giving an
mean density of 30.2.m2 over the whole ground. The macoma biomass estimate was 455.0
tonnes +/- 84.0 tonnes.
Other bivalve species found were:
Angulus tenuis
Donax vittatus
Fabulina fabula
Macoma balthica
ix
North Bank (B)
The North Bank was divided into three areas. The lower western area, surveyed using the
2 stage adaptive process, used a stratum size of 0.618 km2; while the upper western and
eastern areas were each surveyed with a stratified random survey design using a stratum
size 4 times larger at 2.472 km2. The 52 upper and lower western strata along with the
11 eastern strata surveyed gave a combined survey area of 65.55 km2. A total of
228 stations in the eastern, upper western, and both stages of the lower western survey
areas were sampled (Figure 2c). Of these, 184 stations contained a total of 4825 macoma,
an average of 37.7 per station.
The macoma abundance estimate, after the inclusion of both stages of the lower western
area, the upper western and eastern areas was 7240.0 +/- 2291.2 millions giving an mean
density of 211.0.m2 over the whole ground. The macoma biomass estimate was 6420.8 +/1066.7 tonnes
Other bivalve species found were:
Angulus tenuis
Donax vittatus
Fabulina fabula
Macoma balthica
Mya arenaria
Auchencairn (D)
A stratified random survey using a maximum stratum size of 0.100 km2 for each pair of
random stations was carried out at Auchencairn. The survey area contained 37 strata giving
a survey area of 3.457 km2, taking part strata into account. The number of sampling stations
was 74 of which 18 had a total of 75 macoma, an average of 4.2 per station.
The abundance estimate of macoma is 35.4 +/- 19.2 millions giving an mean density of
10.3.m2 over the whole ground. Biomass estimates, shown in the lower half of Table 3d,
behave in a similar way. The macoma biomass estimate is 15.3 +/- 6.5 tonnes.
Other bivalve species found were:
Angulus tenuis
Donax vittatus
Fabulina fabula
Macoma balthica
Orchardton (E)
A stratified random survey with a maximum stratum size of 0.242 km2 for each pair of
random stations was carried out at Orchardton. The survey area contained 6 strata giving a
survey area of 1.032 km2, taking part strata into account. Four of the 12 stations yielded a
total of 41 macoma an average of 10.3 per occupied station. The abundance estimate for
macoma is 26.1 +/-3.9 millions giving an mean density of 25.3.m2 over the whole ground.
The macoma biomass estimate is is 12.5 +/- 18.8 tonnes.
x
Other bivalve species found were:
Angulus tenuis
Donax vittatus
Fabulina fabula
Macoma balthica
Glenisle (F)
A stratified random survey was carried out at Glenisle, with a maximum stratum size of
0.165.km2. Eight strata giving an overall area of 0.659 km2, taking part strata into account.
Eleven out of the sixteen stations yielded a total of 57 macoma giving an average of 5.2 per
station. The abundance estimate for macoma is 28.1+/-9.0 giving an mean density 42.6 m-2
of over the whole ground. The macoma biomass estimate is 9.1+/- 3.4 tonnes.
Other bivalve species found were:
Macoma balthica
Scrobicularia plana
Rough Island (G)
A stratified random survey with a maximum stratum size of 0.165 km2 for each pair of
random stations was carried out at Rough Island. The total area of the 16 strata sampled
was 1.859 km2, taking part strata into account. Nine of the 28 stations yielded a total of 16
macoma giving an average of 1.8 per station. The abundance estimate for macoma is 11.0
+/-8.5 millions giving an mean density of 5.9.m2 over the whole ground. The macoma
biomass estimate is 4.1 +/- 3.6 tonnes.
Other bivalve species found were:
Macoma balthica
Scrobicularia plana
Carsethorn (C)
The survey of Carsethorn was undertaken using a stratified random design limited to the
main bed to the west of the river Nith channel. The maximum size of each of the 35 strata
was 0.128 km2 giving a total survey area of 4.48 km2. A total of 70 stations were sampled
of which 46 contained 860 macoma an average of 18.7 per station. The abundance
estimate for macoma is 550.4 +/- 210.6 millions giving an mean density of 122.9 macoma
·m-2. The macoma biomass estimate for the area of 305.6 +/- 141.5 tonnes.
Other bivalve species found were:
Angulus tenuis
Donax vittatus
Fabulina fabula
Macoma balthica
Mya arenaria
Mytilus edulis
Scrobicularia plana
xi
Arbigland
A stratified random survey design was used at on the Arbigland ground situated to the south
of Carsethorn. The maximum size of the 29 strata sampled was 0.223 km2 giving a total
survey area of 5.284 km2, taking part strata into account. A total of 58 stations were
sampled of which 30 contained 83 macoma an average of 2.8 per station. The abundance
estimate for macoma is 51.0 +/- 22.0 millions giving an mean density of 9.56 macoma ·m-2.
The macoma biomass estimate for the area is 22.8 +/- 13.2 tonnes.
Other bivalve species found were:
Angulus tenuis
Macoma balthica
Mytilus edulis
xii