Argyll Fisheries Trust
Cherry Park, Inveraray, Argyll PA32 8XE Tel: 01499 302 322
Alan Kettle-White: ak@argyllfisheriestrust.co.uk & Jozef Durok: jd@argyllfisheriestrust.co.uk
Scottish Registered Charity No. SCO24181 Reg. 17th Nov. 1995
AFT Biologists Report to Linnhe AMG, Feb 21 2007
River Creran
In 2006 the Argyll Fisheries Trust (AFT) was invited by River Creran fishery interests to
investigate the character and status of migratory fish habitats present in the catchment. The
objectives of this preliminary survey are to;
1. Identify and collate information on the distribution and character of habitat features present
and evaluate the relative condition of habitats in relation to the requirements of migratory
salmonid fish.
2. Provide guidance to potential restoration or enhancement initiatives.
3. Provide a baseline of information upon which to monitor change over time.
4. Advise on the requirement for further survey work through the development of a Fishery
Management Plan.
Habitat Summary
The River Creran is a relatively large (catchment area of 66.7km²) high energy spate river in
North Argyll on the west coast of Scotland. The Argyll Fisheries Trust (AFT) conducted a
habitat survey on the main stem of the River Creran and the River Ure in July 2006 using a
methodology adapted from the Scottish Fisheries Coordination Centre (SFCC) protocols.
The aim of the survey was to evaluate the quantity and quality of freshwater habitats
available to migratory salmon and sea trout. This habitat information may be utilised
alongside other fish and fishery related data to develop a fishery management plan for the
Creran catchment.
River Creran
The River Creran is likely to be accessible to migratory fish for approximately 11km from the
estuary to an impassable waterfall in the upper reaches of the river. Juvenile habitat
appeared to be adequate for fish production throughout most of the catchment, but the
quality of some habitats had been degraded by modifications to the channel morphology.
In-stream habitat
The survey identified that some areas of in-stream substrates upstream of Loch Baile have
been modified, which is likely to have reduced the quality of habitat available to juvenile fish
and may exacerbate instability of substrates in this reach of the river. A degree of instability
of in-stream substrates was also identified further upstream, which may be a consequence of
increased peak flows caused by arterial drainage of the forestry ground. It is recommended
that further survey work will be required to evaluate temporal changes to the modified sites
(after winter spates) and to investigate sources of instability higher in the catchment.
Riparian vegetation
The land use within the catchment is largely coniferous plantations, although broadleaf
woodland, tall herbs and improved grassland are also present. The majority of riparian
habitat appeared to consist of desirable native broadleaf trees as forestry plantations within
the survey sections generally conformed to the recommended guidelines.
River Ure
The River Ure is the largest tributary to the River Creran. The Ure is likely to be accessible to
migratory fish for approximately 3km from the confluence with the main River Creran. The
land is mostly utilised for rough pasture for livestock grazing.
In-stream substrates
In-stream habitat was generally suitable for salmonid fish in the upper reaches of the Ure, but
juvenile fish habitat is less abundant in the downstream reaches due to the construction of
numerous weirs. Although these changes in habitat increase availability of holding water for
adult fish, consequentially it also reduces the abundance of potential habitat available for
juvenile fish production. The weir structures also appear to be causing some erosion of the
banks. It is recommended that a review of the structures are undertaken to verify their
conformity to the Salmon (Fish Passes and Screens) (Scotland) Regulations 1994 and the
Controlled Activities Regulations (SEPA).
Riparian Vegetation
Bankside cover for fish on the Ure is relatively simple in comparison the Creran as no stock
exclusion is present in the riparian zone. A number of alder trees are present, but these are a
relatively old single age class and no or little regeneration is evident.
Fish Survey Summary
In October 2006 the Argyll Fisheries Trust (AFT) was invited by River Creran fishery interests
to investigate the status of salmonid fish populations in the catchment. The objectives of this
survey are to;
1. Provide information on fish distribution in the catchment.
2. Provide estimates of fish abundance in the catchment.
3. Compare fish abundance with similar surveys conducted in 2002 and 2004.
4. Advise on the requirement for further survey work through the development of a Fishery
Management Plan and provide guidance to potential restoration or enhancement
initiatives.
General trends
The surveys suggest that juvenile fish have a similar pattern of distribution compared to
previous surveys with the exception of salmon, which were not present in the upper River
Creran. Abundance of both juvenile trout and salmon in 2006 is generally lower when
compared to previous surveys conducted in 2002 and 2004.
Trout
Trout were well represented throughout the Creran catchment in 2006, but abundance was
relatively low. In general, the results suggest that the numbers of adult sea trout returning to
spawn are currently much lower than that required to repopulate the catchment to optimal
levels.
Salmon
Salmon fry were less well distributed in the Creran catchment than identified in previous
surveys. It is unknown if the lack of juvenile salmon in the upper Creran is an artefact of a
reduction in the numbers of adults returning to spawn or possibly as a result of problems with
water quality, such as acidification. A number of the relatively abundant salmon fry present in
the upper Ure indicated that they were of stocked origin.
Stock status
In general, current salmon and trout fry and parr abundance indicates that current stock
levels remain well below the natural carrying capacity. A combination of factors, such as low
smolt production, limited productivity of freshwater habitats and marine survival issues are
probably limiting the recovery of fish populations in contrast to that reported elsewhere in the
Management area, such as the River Kinglass in Loch Etive (AFT, 2006).
Recommended actions;
No.
Action
1
Lead
Body
ROs
Supporting
Bodies
AFT, Argyll DSFB
Implement a full catch & release angling policy for
salmon and sea trout
2
Continue to monitor trends in distribution &
AFT
ROs
abundance of juvenile fish
3
Develop a catchment specific Fishery
AFT
ROs, Argyll
Management Plan for the River Creran
DSFB, TWG3
4
Inform riparian owners of legislation governing the
Argyll
AMA, AFT
stocking on non-natal fish.
DSFB
5
Monitor trends in sea lice burdens of post-smolt
AFT
TWG, AMG, ROs
sea trout in Loch Creran
6
Conduct Redd counts & snorkel surveys to monitor AFT
ROs
spawning activity throughout the river.
7
Conduct egg hatching experiments in the upper
AFT
Argyll DSFB
River Creran to investigate water quality.
*Note; RO (riparian owner), AFT (Argyll Fisheries Trust), ADSFB (Argyll District Salmon
Fishery Board), AMG (Area Management Group) and TWG3 (Tripartite Working Group
Restoration sub-group 3).
Sea Trout Monitoring – Loch Creran
A total of 552 post-smolt sea trout were sampled during 15 surveys from Loch Creran
between 2003 and 2006. The objective of the programme was to monitor sea lice burdens
and inform members of the Loch Linnhe Area Management Group of on progress on
initiatives undertaken to improve fish health in the area.
Inner and Outer Loch survey sites
The surveys indicated that the sea lice burdens of sea trout sampled in the outer loch sites
were generally higher when compared to those sampled from the inner loch sites. The
differences in lice burdens between sampling sites may potentially be due to the influence of
fresh water entering the inner loch from the River Creran and other coastal streams reducing
salinity and favourable conditions for sea lice to inhabit. There may also be some relationship
to the distance of the surveys site to the nearest fish farm (approximately 3Km for outer loch
sites and nearer 7Km for inner loch sites), but it is also understood from studies of lice larvae
that they may be distributed from a potential point source across a wide area by wind and
tidal flow.
Production Cycles
The data collected indicate that when compared to fish farm production cycles, the levels of
lice infestation on wild fish were lower in the first year of local farm production (i.e. 2004 and
2006) compared to the relatively high infestations identified during the second year of farm
production (2003 and 2005). This relationship between lice burdens of wild fish and fish farm
production cycles has also been reported in other studies. The cyclical nature of lice
infestations on wild fish indicate that both the fallow break at the end of each production
cycle and the strategic use of coordinated sea lice treatments are essential to minimise lice
larvae production on fish farms in Loch Creran and Loch Linnhe.
Potentially lethal lice burdens
Similarly to the relationship between general lice burdens and fish farm production cycles,
the number of fish carrying potentially lethal burdens, according to Bjorn & Finstad (1997),
was highest in the second year of production (2003 and 2005). The percentage of potential
fatalities was approximately 9 and 14% in 2003 and 2005 respectively, indicating that the
survival of sea trout populations were potentially impacted by lice burdens in these years. In
comparison, 3% of samples (one fish) carried potentially lethal lice burdens in 2004 while
there were no fish sampled in 2006 that carried high burdens.
Trends in sea trout abundance
The general trends in the data collected between 2003 and 2006 indicate that the number of
fish sampled in both the inner and outer loch sampling sites has varied year-to-year,
providing sufficient numbers of fish upon which to asses wild fish health during the spring
and early summer period when any post-smolts that potentially have high lice burdens are
more likely to return to freshwater prematurely. The information on post-smolt abundance
may be used with other measures of fish abundance (such as juvenile fish surveys and rod
catch data) to provide an indication of trends in fish abundance in Loch Creran.
Further work
The information on sea lice burdens of sea trout in loch Creran collected to date indicates
that further work is necessary in developing more effective sea lice control strategies in the
second year of production if potential impacts on wild fish are to be avoided. The better
utilisation of the resources available for monitoring of sea trout may be to extend the period
of survey, particularly in the second year of production, to provide more information on the
fate of infected fish.