Biocide Treatment of the Ballachulish Quarry Ponds to
Eradicate American Signal Crayfish
Final Project Report
Lochaber Fisheries Trust
October 2012
Diane Baum, Lucy Ballantyne ‫ ׀‬Lochaber Fisheries Trust Ltd
Torlundy Training Centre ‫׀‬Torlundy ‫׀‬Fort William ‫ ׀‬PH33 6SW
01397 703728 ‫׀‬lochaberfisheriestrust@gmail.com ‫׀‬www.lochaberfish.org.uk
Summary
American signal crayfish were discovered at a pond in Ballachulish Quarry, Lochaber, in
July 2011. This was the only confirmed population in the West Highlands of Scotland
and the spread of this species into neighbouring watercourses could have had devastating
consequences for the region’s freshwater habitats. In June 2012 the pond was treated
with biocide in an attempt to eradicate the crayfish population. The initial results from
post-treatment monitoring suggest the treatment has been effective, but further years of
trapping effort will be required to confirm eradication.
Acknowledgements
Funding for the project was provided by SEPA, SNH and the Highland Council. The
LFT is greatly indebted to all those who gave their time to assist with this eradication
attempt. Without their efforts it would not have been possible. Thanks go to Stuart
Brabbs, Meryl Norris and Gordon MacDermid from the Ayrshire Rivers Trust, Nick
Chisolm and Chris Stones from the Annan Fisheries Trust, Jackie Graham from the
Galloway Fisheries Trust, Kenneth Knott, Henry Dobson, Pete Madden and Jim from
Forestry Commission Scotland, Simon McKelvey and Jill from the Conon DSFB, Keith
Williams and Julie from the Ness and Beauly Fisheries Trust and Niall McLean and
Seymour McLeod from Geo-Rope Ltd for braving the midgies and working like troopers
for no reward. Lucy Ballantyne from LFT, Stephanie Peay and Paul Bryden from SPB
Environmental, Ann Hackett, Nick Aitken, Francie McDade, Eilidh-Ann Madden,
Michelle Melville and Fiona from the Highland Council, Corrina Mertens from SNH and
Kjersti Birkeland from SEPA all worked beyond the call of duty. Forestry Commission
Scotland arrived with a boat, water tank, sprayers and batteries, without which progress
would have been considerably slower. Mel MacAskill and the Ballachulish Community
Council were supportive throughout this project and kindly lent their fencing and allowed
us to take over their shed. Andrew at Loch Ken went to great effort to get us crayfish for
the monitoring. Jon Gibb generously allowed us to use his boat for the duration of the
project. Diane would personally like to thank Lucy for her unfailing support and Niall
for his help with the pumps.
Background
American signal crayfish (Pacifastacus leniusculus) are an invasive non-native species of
freshwater habitats. They were first recorded in Scotland in 1995 and have now been
found in a number of river catchments, mainly south of the central belt. Crayfish are able
to move relatively short distances overland and spread between waterbodies, but most
populations are believed to originate from human introductions. Once the species is
present in a river it can quickly colonise the entire catchment.
The impact of crayfish on aquatic ecosystems can be devastating as they can quickly
become the most numerous species in a waterbody. At high densities they consume large
quantities of aquatic invertebrates and plants, reducing food availability for native species
and altering the ecology of watercourses. They compete with juvenile salmonids for
overwinter shelters and can consume salmonid eggs and fry. In addition, their burrows
can affect the morphology of rivers by exacerbating bank erosion.
There are now tight legal controls on the movement and trapping of American signal
crayfish. The entry of signal crayfish into Scotland is restricted by the Import of Live
Fish (Scotland) Act 1978, Wildlife & Countryside Act 1981, as amended, Conservation
of Native Freshwater Fish Stocks: The Prohibition of Keeping or Release of Live Fish
(Specified Species) (Scotland) Order 2003 and the Nature Conservation (Scotland) Act
2004. Once established in a catchment, it is exceptionally difficult and costly to remove
crayfish. However, small isolated populations have been successfully eradicated by
biocide treatment in Scotland and other parts of the UK (Peay et al. 2006).
In July 2011 American signal crayfish were discovered in the large pond at Ballachulish
Quarry during a pond dipping activity run by Highland Council Rangers. Subsequent
trapping undertaken by the Highland Council in October 2011 confirmed the presence of
crayfish in the large pond, but no crayfish were found in the smaller pond in the quarry.
The Ballachulish population was the only confirmed record of signal crayfish from the
West Highlands. It was later discovered that the source of the population was a
deliberate release of about a dozen crayfish into the pond by a local resident
approximately 12 years ago.
Site Characteristics
The infected pond is in a disused slate quarry in the village of Ballachulish, Lochaber
(NN08523 58252, Figure 1). It is an artificial waterbody that formed when quarrying
ceased at the site in 1955. After the quarry closed the pits were partially filled with
unconsolidated slate before being allowed to fill with water creating two ponds on the
site. The infected pond is the larger of the two ponds on the quarry site.
The volume of the infected pond was estimated in January 2012. The surface area of the
pond was approximately 19 500m2 based on measurements taken from aerial
photographs. Pond depth was measured at 100 points along transects across the pond
using a plumbline (Figure 2). The average depth was 2.35m. The margins of the pond are
relatively shallow, with the deepest part towards the southeast end where the water
reaches a maximum of 12m in depth (Figure 2). From these measurements, the volume
of the infected pond was estimated to be 46 000m3, and it is this figure that was used to
calculate the amount of biocide needed to treat the pond. However, the depth
measurements were taken during a period of heavy rainfall. When the biocide treatment
occurred in June, the depth of the pond was up to 0.5m lower than in January, and the
volume of the pond was probably closer to 35 000m3.
The infected pond has no surface connection to any other waterbody. The nearest
waterbody is a second, smaller pond within the quarry site, approximately 50m from the
infected pond. The small pond has a surface area of 4 250m2 and an average depth of
2.05m (measured by the same method described above). The nearest natural freshwater
waterbody to the infected pond is the River Laroch, 400m away (Figure 1). Loch Leven,
a narrow, sheltered sea loch is approximately 300m north of the quarry (Figure 1).
Small pond
Infected pond
Loch Leven
Storm drain outfall
Small pond
Infected pond
River Laroch
Figure 1. Photograph and map showing the position of the infected pond in relation to
the small pond, River Laroch and Loch Leven.
1
2
3
4
5
6
7
8
9
11
10
12
Legend
1
Survey transect
Approximate depths
0-1m
50m
1-2m
2-3m
3-12m
Figure 2. Approximate bathymetric profile of the infected pond. Produced from depth
sampling with a plumbline along transects rowed by LFT staff 19/1/2012.
The infected pond is surrounded on three sides by steep-sided quarry walls Figure 3).
The unconsolidated slate that makes up much of the bed and banks of the south and east
ends of the pond provides excellent refuge habitat for crayfish. The northeast side of the
pond is more open, and gently sloping banks covered in grass and scrub rise to at least
1.5m above the level of the pond. There is less cover available for crayfish on this side of
the pond as the substrate and banks are generally composed of silt or small pebbles. On
the west side of the pond there is a small fringe of sedges along the water margin and
there is a stand of pondweed in the centre of the pond. However, the large pond and its
margin are largely devoid of vegetation. The small pond has much lower banks covered
in grass and scrub vegetation. There is abundant growth of submerged vegetation in the
small pond.
Figure 3. The infected pond viewed from the gently sloping northeast bank looking
towards the steep quarry faces on the south and west sides.
The catchment of the quarry extends to approximately 0.5km2 covering open hillside and
some planted forestry (Figure 4). There are no permanent inflow channels entering either
pond. For most of the year a small waterfall flows down the southeast wall of the quarry
and into the large pond. This is the result of drains dug to prevent water entering the
quarry that were subsequently dammed to stop flooding at Tigh-phuirt and diverted back
into the quarry. During dry periods this inflow dries up completely. Following high
rainfall water drains into the large pond from numerous temporary channels on the steep
quarry walls on three sides of the pond.
Figure 4. The catchment of the quarry ponds with the village of Ballachulish in the
foreground.
There is no history of the infected pond or the small pond flooding. There is likely to be
some seepage from the infected pond as the slate substrate is porous. However, it appears
that seepage between the infected and the small pond is minimal as the water level of the
small pond is higher following heavy rain. A storm drain links the small pond with Loch
Leven (Figure 1). At low water levels the small pond is below the level of the drain, but
it does flow during periods of high rainfall.
Ballachulish Quarry is owned by The Highland Council and managed by the Ballachulish
Community Council. The quarry site is used by the local community and visitors to the
area. There are paths, interpretation panels and a picnic site in the quarry. Canoe groups
regularly use the pond for practice sessions.
Pre-treatment Monitoring
Kick sampling carried out by Highland Council Rangers has indicated that relatively few
species are present in the pond, possibly reflecting the short length of time the pond has
been in existence (Table 1). Brown trout and European eel have historically been stocked
into the ponds, but high summer temperatures have caused periodic mortality of these
species in the past preventing the establishment of a self-sustaining population.
Table 1. Species recorded from the infected pond during kick sampling surveys.
Group
Fish
Common name
Brown trout
European eel
Three-spined stickleback
Scientific name
Salmo trutta
Anguilla anguilla
Gasterosteus aculeatus
Amphibians
Palmate newt
Common frog
Triturus helveticus
Rana temporaria
Insects
Lesser water boatman
Whirligig beetle
Corixa spp.
Gyrinus substriatus
Mollusc
Pond snail
Lymnaea spp.
Crustacea
American signal crayfish
Pacifastacus leniusculus
In September 2011 the Highland Council carried out trapping under licence from Marine
Scotland to assess the presence and relative abundance of crayfish in the two quarry
ponds and the River Laroch. The results of the trapping are presented in table 2. No
crayfish were found in the small pond or River Laroch, though the trapping effort was
insufficient to conclusively rule out their presence. Crayfish were present in the large
pond. Densities were low relative to well-established populations such as those on Loch
Ken.
Table 2. Results of crayfish trapping undertaken in the Ballachulish area in September
2011.
Number of crayfish caught
Date
7/9/2011
8/9/2011
9/9/2011
20/9/2011
21/9/2011
22/9/2011
23/9/2011
27/9/2011
28/9/2011
29/9/2011
30/9/2011
Total
CPUE (crayfish/trap/day)
Big pond
Small pond River Laroch
(6 traps)
(4 traps)
(4 traps)
3
2
No trapping
2
1
6
0
No trapping
No trapping
No trapping
No trapping
14
0.39
0
0
0
0
0
0
0
No trapping
No trapping
No trapping
No trapping
0
0
No trapping
No trapping
No trapping
No trapping
No trapping
No trapping
No trapping
0
0
0
0
0
0
Eradication method
Permissions
Permissions to carry out the biocide treatment were obtained from the relevant
authorities.
The biocide application was carried out under CAR Registration
CAR/R/1102118 issued by the SEPA office in Fort William. The biocide used (Pyblast)
is not licenced in the UK for use in the aquatic environment. Therefore an Automatic
Experimental Permit was obtained from the HSE Biocide Unit. All trapping, transport,
holding and release of live crayfish was carried out under licences obtained from Marine
Scotland.
Site Preparation
The storm drain linking the small pond at the quarry and Loch Leven was temporarily
blocked on 7th June. It remained blocked throughout the treatment period and until 9th
July when the toxicity of the large pond had declined significantly.
The inflow into the large pond was diverted on 9th June and restored on the 16th following
application of the biocide. Old drainage ditches were dug on the hill above the pond to
prevent water entering the quarry. A large earth dam was subsequently installed on the
main ditch to prevent flooding of Tigh-phuirt and create the waterfall flowing into the
quarry. This dam was not removed, but small plastic and earth dams were installed
upstream of it and the water diverted through six inch drainage pipe away from the
quarry catchment.
Pre-treatment Monitoring
There is no chemical test to allow the concentration of Pyblast in the pond to be
measured. Instead a bioassay was used to estimate the Pyblast concentration. This
requires the Lc50 (concentration at which 50% mortality is recorded) for Pyblast to be
established for a test species. The bioassay involves exposing the test species to various
dilutions of the pond water and using the mortality rate to back-calculate the Pyblast
concentration. In past eradication attempts, the freshwater shrimp Gammarus pulex has
been used for the bioassays. This species is not present in the Ballachulish ponds and is
rare throughout Lochaber due to the naturally low pH of the water. Attempts were made
to establish a dose response curve and Lc50 for the freshwater hoglouse, Asellus
aquaticus, which is present at the small pond in Ballachulish Quarry and at sites across
Lochaber. Three attempts were made between 8th May and 4th June but all Asellus died
even at 0.01ųgl-1, the lowest concentration of pyrethroid tested. No other invertebrate
species was present at the quarry in sufficient numbers to make them suitable for the
bioassay. Instead Gammarus were sourced from Ayrshire and Yorkshire for the dose
response test and post-treatment bioassays. The results of the preliminary dose response
test are presented in appendix 3. The Lc50 for Gammarus was approximately 5ųgl-1.
A total of 300 crayfish were required to test the efficacy of the biocide treatment (see
later monitoring section) and for preliminary tests to ensure the proposed dose rate of
Pyblast would be sufficient to kill them under local conditions. The density of crayfish at
the Ballachulish ponds was too low to allow this number of crayfish to be caught over a
short period of time. Loch Ken in Dumfrieshire has a long-established and dense
population of American signal crayfish and the test crayfish for this project were sourced
from there. Four barrel traps were set in Loch Ken on 4th June and lifted on 8th June. The
crayfish were transported to the Ballachulish Community Council shed on 8th June in
secure containers and held here until needed under licence from Marine Scotland.
Pre-treatment tests of the response of American signal crayfish to varying concentrations
of Pyblast in water and substrate taken from the Ballachulish ponds were conducted on
9th June. Six 30l tanks were lined with rocks and silt taken from the large quarry pond
and filled to 20l with pond water and sufficient Pyblast to achieve 0, 0.1, 0.2, 0.3, 0.5 and
1mgl-1 of pyrethroids. 10 crayfish from Loch Ken were placed in each tank at 18:00 on
9th June. Mortality of the crayfish was checked 24 hours later. All crayfish in the control
tank survived. All crayfish exposed to Pyblast in concentrations from 0.1 to 1mgl-1 died
within 24 hours.
Fencing was erected around the ponds on the 11th June to deter members of the public
from entering the ponds during the treatment. Signs were displayed on site to provide
information about the purpose of the treatment.
Biocide Treatment
The large pond at Ballachulish Quarry was treated with Pyblast, a natural pyrethroid
derived from chrysanthemums. The formulation of Pyblast contains 3% w/w natural
pyrethrins that act as a powerful neurotoxin. Pyblast is highly toxic to crayfish and has
been used in previous successful eradication attempts in Scotland (Peay et al. 2006) and
England. It has low toxicity to mammals and birds and does not bioaccumulate in these
taxa. Based on previous eradication attempts and the dose tests carried out prior to the
Ballachulish treatment (see above), a target dose rate of 0.3mgl-1 was set for the large
pond. This required a total of 460l of Pyblast (1.38kg pyrethrin) to be applied to the
pond. Pyblast was diluted in the ratio 1:7 with pond water to allow it to be sprayed onto
the pond.
Pyblast was applied to the large pond by boat-mounted sprayers with battery powered
pumps (Figure 5). Three boats were used on the large pond on 12th June, two with 98l
Figure 5. Pyblast being applied to the large pond from boat-mounted sprayers.
spray tanks and the third with a 60l tank. Tanks were connected to lances fitted with anvil
nozzles. The pond was divided into three zones of approximately equal water volume
and one boat was allocated to each zone (Figure 6). A minimum of two people were
present on each boat: one oarsman and at least one person operating the sprayer. The aim
was to achieve good coverage of the entire pond surface, with more Pyblast applied on
areas of deep water. Pyblast is denser than water and should sink to the bottom of the
pond where the crayfish are present. The spraying lasted approximately 8 hours from
10am in the morning to 6pm in the evening. Refilling of the tanks took place on the
shore and a record was kept of the refills to ensure each zone received the correct amount
of Pyblast.
Legend
2” pump
Fuel bowser
4” pump
Pyblast refilling site
Zone 1
Zone 3
Zone 2
Figure 6. Division of large pond into zones for Pyblast treatment and position of pumps
and refilling stations.
In addition to the boast sprayers, backpack sprayers were used to treat a 1m band around
the edge of the pond and the shallow margins of the pond that were inaccessible to the
boats (Figure 7). This was easily achieved on the north and east sides of the pond where
the bank is shallow, but the steep walls on the south, and to a lesser extent, west sides of
the pond made walking difficult. To ensure the banks were covered, the boats in these
zones sprayed onto the shore and into the bank wall.
Figure 7. Pyblast being applied to the pond margin from a backpack sprayer.
To ensure water-filled crevices in the slate along the south and west banks were flooded
with Pyblast, buckets were used to douse the banks with treated pond water. Dead
crayfish were visible at the margins of the pond within an hour of the treatment
commencing (Figure 8).
Figure 8. Dead crayfish at the pond margin following Pyblast application.
At the end of the spraying, a boat with a 60hp outboard engine supplied by Geo-Rope Ltd
was driven around the pond to aid mixing of the Pyblast and create waves forcing water
into the vertical banks on the south side of the pond.
Test cages of crayfish (see below) were lifted from the large pond at about 7:30pm on
12th June after the biocide had been applied. All crayfish in the shallow cages were dead
or torpid. However, crayfish from cages 7 and 13, which were positioned in water
greater than 4m deep contained crayfish that were still self-righting. The Pyblast had not
sunk to the bottom in the deep parts of the pond. The LFT took the decision to use the
Pyblast intended for treatment of the small pond to instead increase the dose rate in the
deeper part of the large pond. Pyblast was diluted with pond water in the ratio 2:1 and
sprayed down 6m rigid hoses held vertically from the boat. There was some drag on the
hoses but the rowing speed was moderated to ensure Pyblast was delivered at least 4m
below the surface of the water. A total of 20l of Pyblast was applied to the deepest area
of the pond before darkness fell.
On the 13th June treatment of the deep areas resumed using the same method as the night
before, but with two boats spraying in each of the two deep zones in the pond (Figure 2).
Prior to the application, an underwater camera was used to locate the deepest trenches in
the pond and these were marked with floats to aid the boats. A total of 120l of Pyblast
was applied to the deep areas, 70l in the southeast hole and 50l in the southwest hole.
There was no clear thermocline present in the pond that could account for the Pyblast not
sinking to depth. Temperature recordings taken from the pond on the 13th June showed
no distinct change in temperature other than at the very surface, which the Pyblast
penetrated successfully. Instead it is likely that the Pyblast simply dissipates as it sinks
through the water column, and below 3-4m most fails to reach the bottom.
The decision to use the remaining Pyblast to treat the deep parts of the large pond meant
the small pond was not treated. The results of subsequent intensive trapping (see below)
indicated crayfish were not present in the small pond and it remains untreated.
Post-treatment site management
Once the Pyblast application had finished, pumps were run to circulate treated water in
the large pond. Access difficulties limited the size and position of pumps used. A 4”
pump was placed on the north shore of the pond and two 2” pumps were positioned as
shown in figure 6. The size of the pond and restricted vehicle access precluded effective
circulation of the entire pond. The pumps were run for 3 hours on the afternoon of the
13th and for 8 hours a day on the 14th and 15th of June.
The toxicity of the pond had declined significantly by the 15th June and the pond water
was probably no longer lethal to crayfish. On 16th June the emphasis switched from
circulating the biocide to pumping the pond water onto the ground to speed up the
breakdown of the Pyblast and hence the recovery of the pond. The pumps were left in
their original positions, but the hoses were changed to lengthen the intake hoses and
repositioning the outflow so that it discharged onto vegetated ground. Contact with
sediment should speed the breakdown of the Pyblast. The pumps were run in this
configuration from 16th to the 22nd June.
Bioassays were run on the pond water to monitor its toxicity. By 11th July the
concentration of Pyblast in the pond was estimated to be 10μgl-1 (one hundredth of the
concentration achieved on the day of treatment) and it was judged safe to remove the
fences from the quarry and re-open the ponds to the public.
Monitoring
The effectiveness of the treatment was monitored by placing cages of Loch Ken crayfish
into the pond prior to the treatment and monitoring their mortality once the biocide had
been applied. 13 cages each containing 10 crayfish were placed around the large pond on
11th June (Figure 9). The cages were weighted and sat on the pond bed at various depths
depending on their position in the pond.
Figure 9. Cages containing crayfish from Loch Ken used to test the efficacy of the
biocide treatment. Photo courtesy of S. Peay.
Some cages were inspected at 19:30 on 12th June approximately 1.5hrs after the treatment
of the large pond had finished. The condition of these crayfish was not systematically
recorded, but the crayfish that had been held at depth were seen to be sufficiently active
to trigger further treatment of the deep areas of the large pond (see above). The test cages
were returned to their original locations prior to the additional Pyblast application on the
evening of 12th June and an additional test cage (cage 19) containing 10 crayfish was
introduced to the deepest part of the pond at 23:30 on 12th June. All crayfish cages were
lifted at 09:00 on 13th June and the activity of the crayfish was examined on the shore and
categorised according to the definitions in table 3.
Table 3. Definitions used to assess the condition of test crayfish
Condition
Self-righting
Slow self-righting
Not self-righting
Torpid
Dead
Description
Normal condition, no apparent effect
Movement slow and often stiff, may take 1 minute or more to
turn over if placed on back even in water
Significantly affected, lying on back, but still making voluntary
movements of limbs in water or air
No voluntary movement, lying on back, will show slight
movement of limbs when touched, but in more advanced stages
moribund animals may show minimal response or just
movement of mouthparts
No response to touching. No eye-stalk response
The condition of the test crayfish is presented in table 4. Most crayfish were torpid or
dead. The cages positioned in the deep part of the southeast corner of the pond that had
been found to contain active crayfish on the evening of 12th (cage 13) contained mainly
torpid or dead crayfish on the morning of the 13th June following the additional Pyblast
application to this area of the pond. The crayfish in cages in the deep area of the
southwest part of the pond (cages 3, 7) were still very active on the morning of the 13th.
All crayfish that were still alive at 09:30 on 13th were exposed to untreated pondwater
from the small pond to test their ability to recover from the dose they had received.
These crayfish were rechecked at 16:45 on the 13th and all but three were found to be
dead. The other three were torpid and did not recover.
The exception were the very active crayfish in tank 7 that were not put in untreated pond
water, but were returned to their original position in the large pond at 16:00 on the 13th.
In addition another 11 traps each containing 10 crayfish that had not previously been
exposed to treated water were placed in the pond at 16:00 on the 13th June following
completion of the additional treatment of the deep areas in the large pond. The 12 cages
were lifted at 10:00 on the 14th June and the condition of the crayfish in each cage
recorded (Table 5). All crayfish were either torpid or dead. Torpid crayfish were
returned to cages placed in the margin of the large pond and rechecked at 16:00 on the
14th June (Table 5). Most crayfish were dead. The nine that still displayed an eye-stalk
response were placed in untreated pond water from the small pond and all were dead
when checked at 20:00.
The storm drain connecting the small quarry pond to Loch Leven had been blocked prior
to treatment, but to ensure no Pyblast was entering the loch test cages of amphipods were
placed at the outflow of the drain (Figure 1). Approximately 20 amphipods caught on the
margin of the loch were placed in each of two cages. These were monitored twice daily
between 12th and 17th June. No mortality was recorded.
Post-treatment monitoring
Bioassays on water from large pond
To monitor the breakdown of Pyblast, Gammarus were exposed to different dilutions of
water from the large pond in the days and weeks following treatment. Pre-treatment
trials had shown the Lc50 for Gammarus was approximately 5μgl-1 for natural
pyrethroids. Using this information it was possible to estimate the concentration of
pyrethroids in samples of pond water taken from the shallow margin on the northeast side
and the deep hole on southeast side of the treated pond (Figure 2). Concentrations of
Pyblast immediately following treatment on 13th June reached 0.75mgl-1 in the deep
water and 1.2mgl-1 in the shallow margins. These exceeded the original target dose rates
since an additional 160l of Pyblast had been applied to the large pond had been and the
dry period preceding treatment meant the pond volume was lower than when the
calculations were made. The concentration of pyrethroids in both the shallow and deep
water declined rapidly as the Pyblast broke down (Figure 10). By the 14th August the
pond water was not toxic to Gammarus.
-1
1.4
Shallow sample
Deep sample
1
0.8
0.6
0.4
0.2
14/08/2012
10/08/2012
12/08/2012
08/08/2012
06/08/2012
02/08/2012
04/08/2012
31/07/2012
29/07/2012
25/07/2012
27/07/2012
23/07/2012
21/07/2012
17/07/2012
19/07/2012
15/07/2012
13/07/2012
09/07/2012
11/07/2012
07/07/2012
05/07/2012
01/07/2012
03/07/2012
29/06/2012
27/06/2012
23/06/2012
25/06/2012
21/06/2012
19/06/2012
15/06/2012
17/06/2012
0
13/06/2012
Estimated concentration pyrethroids mgl
1.2
Date
Figure 10. Decline in estimated Pyblast concentration in the large pond following
application on the 12th June.
Table 4. Condition of test crayfish introduced to the large pond on 11th June prior to Pyblast treatment. Numbers in brackets relate to
the condition of the crayfish when rechecked at 16:45 after exposure to untreated pondwater.
Cage
Depth
number (m)
1
6
2
2
3
3
4
2
5
6
6
1.5
7
4
8
1
9
1
10
2
11
1.5
12
2
13
10
Time
introduced
pond
11/06/2012
18:00
11/06/2012
18:00
11/06/2012
18:00
11/06/2012
18:00
11/06/2012
18:00
11/06/2012
18:00
11/06/2012
18:00
11/06/2012
18:00
11/06/2012
18:00
11/06/2012
18:00
11/06/2012
18:00
11/06/2012
18:00
12/06/2012
23:30
Time checked
to
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
13/06/2012
09:30
Time
rechecked
13/06/2012
16:45
13/06/2012
16:45
13/06/2012
16:45
13/06/2012
16:45
13/06/2012
16:45
13/06/2012
16:45
Not rechecked –
returned to pond
13/06/2012
16:45
13/06/2012
16:45
13/06/2012
16:45
13/06/2012
16:45
13/06/2012
16:45
13/06/2012
16:45
Number of crayfish
SelfSlow self- Not self- Torpid
righting
righting
righting
Dead
0 (0)
0 (0)
0 (0)
10 (2)
0 (8)
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
0 (0)
1 (0)
4 (0)
3 (0)
2 (10)
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
0 (0)
0 (0)
0 (0)
2 (0)
8 (10)
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
7
3
0
0
0
0 (0)
0 (0)
0 (0)
3 (0)
7 (10)
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
0 (0)
0 (0)
0 (0)
2 (0)
8 (10)
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
0 (0)
0 (0)
0 (0)
4 (0)
6 (10)
0 (0)
0 (0)
2 (0)
4 (1)
4 (9)
Table 5. Condition of test crayfish introduced to the large pond on 13th June following further Pyblast application to the deep areas.
Numbers in brackets relate to the condition of the crayfish when rechecked at 16:00 after being placed in the pond margin.
Cage
Depth
number (m)
7
4
a
1
b
1.5
c
3
d
10
e
1.5
f
2
g
7
h
6
i
1.5
j
2.5
k
6
Time
introduced
pond
13/06/2012
16:00
13/06/2012
16:00
13/06/2012
16:00
13/06/2012
16:00
13/06/2012
16:00
13/06/2012
16:00
13/06/2012
16:00
13/06/2012
16:00
13/06/2012
16:00
13/06/2012
16:00
13/06/2012
16:00
13/06/2012
16:00
Time checked
to
14/06/2012
10:00
14/06/2012
10:00
14/06/2012
10:00
14/06/2012
10:00
14/06/2012
10:00
14/06/2012
10:00
14/06/2012
10:00
14/06/2012
10:00
14/06/2012
10:00
14/06/2012
10:00
14/06/2012
10:00
14/06/2012
10:00
Time
rechecked
14/06/2012
16:00
14/06/2012
16:00
14/06/2012
16:00
14/06/2012
16:00
14/06/2012
16:00
14/06/2012
16:00
14/06/2012
16:00
14/06/2012
16:00
14/06/2012
16:00
14/06/2012
16:00
14/06/2012
16:00
14/06/2012
16:00
Number of crayfish
SelfSlow self- Not self- Torpid
righting
righting
righting
Dead
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
0 (0)
0 (0)
0 (0)
2 (1)
8 (9)
0 (0)
0 (0)
0 (0)
4 (2)
6 (8)
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
0 (0)
0 (0)
0 (0)
4 (2)
6 (8)
0 (0)
0 (0)
0 (0)
1 (0)
9 (10)
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
0 (0)
0 (0)
0 (0)
6 (3)
4 (7)
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
0 (0)
0 (0)
0 (0)
4 (1)
6 (9)
0 (0)
0 (0)
0 (0)
0 (0)
10 (10)
Crayfish trapping in the Small Pond
No crayfish had been recorded from the small pond, but the intention had been to treat it
with biocide as a precaution. The use of the Pyblast intended for the small pond to treat
the deep areas of the large pond meant this was no longer possible within the original
project. In order to establish if crayfish were present in the small pond and further
funding and staff time would need to be sought to treat it, intensive trapping of the small
pond was carried out between 13th and 24th June. 20 fladden traps were deployed in the
pond resulting in a total of 220 trap nights. No crayfish were trapped on the small pond.
On the 13th June a 1m wide band at the southern margin of the small pond was sprayed
with Pyblast from a backpack sprayer. In the large pond dead crayfish were very visible
at the margin soon after spraying. After spraying in the small pond, dead stickleback and
tadpoles were seen, but no crayfish.
It was therefore concluded that crayfish weren’t present in the small pond and the pond
was not treated with biocide. Traps will be used to monitor the small pond in the future
to ensure crayfish are not present.
Crayfish trapping in the large pond
The biocide treatment will only have been effective if all crayfish in the large pond have
been killed. Even if only a few crayfish survived, these could quickly multiply and
recolonise the pond. To assess the effectiveness of the project intensive trapping was
carried out two months after the treatment. 20 fladden traps were set on the large pond
on 21st August 2012. The traps were concentrated in the south and west ends of the pond
where the crayfish density had been highest and in the two deepest parts of the pond
where the Pyblast was least like to have reached. All traps were checked daily until 2nd
September, resulting in a total of 240 trap nights. No crayfish were caught during the
trapping. It is possible that a very small population of crayfish would not be detected by
even intensive trapping and so this trapping effort will need to be repeated for a further
four years to be confident that crayfish have been eradicated form the pond.
Crayfish trapping in other waterbodies
Crayfish have been present in the Ballachulish quarry pond for over a decade. It is
possible that in that time crayfish have migrated from the pond or have been moved by
humans or potential predators to neighbouring waterbodies. To assess the potential
spread of the crayfish, trapping was carried out in Loch Achtriochtan and Glencoe
Lochan and electrofishing and kick sampling on the Rivers Laroch and Coe. The
National Trust for Scotland set 10 fladden traps on Loch Achtriochtan and checked them
daily between 23rd and 31st July. Forestry Commission set 10 fladden traps in Glencoe
Lochan and checked them daily between 30th July and 3rd August. No crayfish were
recorded from either loch. Electrofishing and kick sampling surveys of the Rivers Laroch
and Coe were carried out by the LFT on 28th September. No crayfish were recorded from
either river.
Recommendations for future biocide treatments







In water greater than 3m deep surface spraying is not sufficient to ensure a lethal
concentration of Pyblast will reach the substrate. A boat-mounted pressure
washer with 5m lance would allow Pyblast to be applied effectively to deep water.
A pressure washer would also allow Pyblast to be sprayed horizontally into
vertical faces containing crayfish refuges such as the unconsolidated slate that
made up large sections of the Ballachulish Quarry pond wall.
Dilute Pyblast is dense, but some was still lost as aerosol during the spraying. If
sufficient pressure can be maintained, then the Pyblast should be sprayed slightly
below the water surface to reduce this loss.
For large waterbodies it would be useful to have personnel with PA5 certificates
and boat-mounted boom sprayers. This would greatly increase the speed of
application and reduce the staff resource required.
The endoscope camera provided invaluable information about the pond
bathymetry. Where possible this should be used at an early stage of the project
planning to identify suitable crayfish habitat at depth.
In large ponds with poor vehicle access, an outboard motor with a long prop is
probably much more effective at mixing the Pyblast than anything that can be
achieved by pumps located on the banks.
Pumping the water to ground to break down the Pyblast is probably not necessary
in contained ponds. This should be retained as a contingency, but the resources
would be better directed to other areas of the treatment.
References
Peay, S., Hiley, P.D., Collen, P. & Martin, I. (2006). Biocide treatment of ponds in
Scotland to eradicate signal crayfish. Bull. Fr. Pêche Piscic. 380-381: 1363-1379.
Appendix 1- Project Costs
Equipment Costs
Description
Pyblast
Pump and hose
hire
Diesel for pumps
Fuel bowser hire
Water bowser
hire
Tank sprayers
12V batteries
Backpack
sprayers
Spare lance
PPE –
Cost per unit
£54.57
Number of units
620l
Delivery
-
Total cost
£33 835.63
£1730.00
£0.798
£54
£42
1000l
2 weeks
2 weeks
£120
£120
£798
£228
£204
£149.99
£85.99
£29.22
2
3
2
£22.14
-
£322.12
£257.97
£58.44
£6.69
1
-
£6.69
Nitrile gloves
£5.95
2
-
£11.90
PU gloves
£1.94
4
-
£7.76
Goggles
£2.93
5
-
£14.65
1
3
£4.99
£17.74
£27.85
1
1
-
£12.99
£35.99
1
2
20
12
-
£8.10
£5.68
£132.00
£40.00
1
£3.50
£7.45
3
6
-
£11.13
£25.20
8
1
-
£6.39
£12.00
Eyewash kit
£17.74
Pond liners to
£7.62
dam inflow
Garden hose
£12.99
Absorbent fleece
£35.99
matting
Fuel funnel
£8.10
Plastic funnel
£2.84
Crayfish traps
£6.60
Tanks for
£3.33
crayfish tests
Measuring
£3.95
cylinder
Measuring jugs
£3.71
Clamps for
£4.20
sprayers
Jubilee clips
£0.64-3.12
Disposal of
£12.00
Pyblast
containers
Total Equipment Cost
37 817.68
Staff Costs
Activity
Organisation
Inflow diversion
Block storm
drain
Trap test crayfish
Transport test
crayfish
Crayfish dose
response test
Site preparation
Bioassays
Pyblast
application
Assistance with
Pyblast
application
Pump to circulate
Pyblast
Pump to ground
Crayfish trapping
– Ballachulish
Quarry
Crayfish trapping
– Glencoe
Lochan
Crayfish trapping
– Loch
Achtriochtan
Project
consultant
Project
management
Project
management
Report
preparation
Total staff costs
Cost per day
Total
LFT
THC
Number of man
days
1
1
£150
£150
£150
£150
GFT
LFT
2
1
£360
£150
£720
£150
LFT
1
£150
£150
LFT, THC
LFT, THC
LFT, FC, ART,
AFT, GFT,
CDSFB, NBFT
THC, SEPA,
SNH
6
12
28
£150
£150
£300
£900
£1 800
£8 400
8
£150
£1 200
LFT, THC, GR
6
£150
£900
LFT, THC, GR
LFT, THC
13
20
£150
£150
£1 950
£3 000
FC
4
£150
£600
NTS
4
£150
£600
SPBE
10
£400 + T&S
£4 742.40
LFT
25
£300
£7 500
THC
5
£300
£1 500
LFT
3
£300
£900
£35 312.40
Abbreviations: LFT – Lochaber Fisheries Trust; THC – Highland Council; GFT – Galloway Fisheries
Trust; FC – Forestry Commission Scotland; ART – Ayrshire Rivers Trust; AFT – Annan Fisheries Trust,
CDSFB – Connon District Salmon Fishery Board; NBFT – Ness and Beauly Fisheries Trust; SEPA –
Scpttish Environment Protection Agency; SNH – Scottish Natural Heritage; GR – Geo-Rope Ltd; NTS –
National Trust for Scotland; SPBE – SPB Environmental.
Total project costs £73 130.08
Contingency Costs (budgeted for but not required for this project)
Pump Hire – 2 week hire including couplers, hoses and delivery = £1 109.00
Diesel – 40l per day for 12 days @ £1.45 per litre = 696.00
Pumping water to ground – 12 man days @ £150 per day
Total cost - £3 605.00
Appendix 2 - Funding Sources
Highland Council
Equipment costs - Cash - £4 702.05 + contingency
In kind - £7 950
SEPA
Chemical costs - Cash - £33 835.63
In kind - £150 (1 man day @ £150)
SNH
Project management and consultant - Cash - £13 081.75
In kind - £150 (1 man day @ £150)
Lochaber Fisheries Trust
In kind - £4 560.65
Fishery Trust Biologists
In kind - £6 000 (20 man days spraying Pyblast @ £300)
Forestry Commission
In kind - £1 800 (4 man days Pyblast spraying @ £300; 4
man days crayfish trapping @ £150)
National Trust for Scotland In kind - £600 (4 man days crayfish trapping @ £150)
Geo-Rope Ltd
In kind - £300 (2 man days @ £150)
Total - £73 130.08
In-kind donations of equipment:
Forestry Commission Scotland – Boat, water tank, spray tank, 2 backpack sprayers, 3
12V batteries.
Ballachulish Community Council – Haras fencing.
Ayrshire Rivers Trust – 3 backpacks, endoscope camera.
Geo-Rope Ltd – Boat, rope.
Jon Gibb – Boat, jerry cans.
Appendix 3 – Results of Gammarus dose response test
Method: 10 Gammarus were placed in tanks containing water from the small quarry
pond and sufficient Pyblast to achieve concentrations of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and
10μgl-1 of natural pyrethroids. Three replicate tanks were set up for each treatment. The
number of dead Gammarus in each tank was recorded 24 hours later.
NUm ber dead after 24hrs
Results: The number of Gammarus dead in each treatment after 24 hour exposure to the
Pyblast is shown in the graph below. There is some scatter in the results and Gammarus
died in the controls containing only pond water. However, the results suggest an Lc50 of
approximately 5μgl-1 for Gammarus exposed to natural pyrethroids.
10
9
8
7
6
5
4
3
2
1
0
0
2
4
6
P ybla st c onc e ntra tion (ųg l-1)
8
10