WESTCOUNTRY RIVERS TRUST ELECTROFISHING SURVEY REPORT - RIVER FOWEY, 2020 - Westcountry Rivers Trust Electrofishing Survey Report - River Fowey ...
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Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
WESTCOUNTRY RIVERS TRUST River Fowey
ELECTROFISHING SURVEY
REPORT- RIVER FOWEY, 2020
0
Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Report written by Craig Renton
Mapping undertaken by Craig Renton
Checked by Bruce Stockley
Westcountry Rivers Trust
Rain-Charm House
Kyl Cober Parc
Stoke Climsland
Callington
Cornwall
PL17 8PH
Tel: +44 (0) 1579 372140
Email: info@wrt.org.uk
Web: www.wrt.org.uk
Version Details of Revision Prepared by Checked by Approved by Date of Issue
Draft For client comment Craig Renton Bruce Stockley Bruce Stockley 11/01/21
Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Contents
Executive Summary................................................................................................................................. 1
1. Introduction .................................................................................................................................... 1
1.1 Electrofishing Protocols ................................................................................................................ 1
1.2 Life cycle and bottlenecks ............................................................................................................. 3
1.3 Catchment Based Fisheries Conservation Strategy (Defend/Repair/Attack) ............................... 4
2. Site selection ................................................................................................................................... 4
3. Field Sampling and data analysis methods ..................................................................................... 5
4. Results and Discussion .................................................................................................................... 7
5. Recommendations ........................................................................................................................ 19
6. Acknowledgments......................................................................................................................... 22
Table of figures
Figure 1 Diagrams defining salmonid habitat bottlenecks (Summers et al, 1996) ................................. 4
Figure 2 2020 Fowey Salmon Length Frequency Distribution. ............................................................... 6
Figure 3 2020 Fowey Trout Length Frequency Distribution. .................................................................. 7
Figure 4 Total catch data for River Fowey, 2020 .................................................................................... 8
Figure 5 Salmon and trout classifications River Fowey, 2020................................................................. 9
Figure 6 Fowey trout fry classification stacks. ...................................................................................... 16
Figure 7 Fowey salmon fry classification stacks.................................................................................... 16
Figure 8 Multi-year average fry numbers for salmon, trout and combined salmonids. ...................... 17
Table 1 Semi-quantitative abundance categories for salmon fry (Crozier & Kennedy, 1994) ............... 6
Table 2 Fowey Salmon & Trout Fry Classifications 2020. ....................................................................... 7
Table 3 Multi-year salmon fry classifications (N.B hatched areas are Environment Agency surveys). 12
Table 4 Multi-year trout fry classification (N.B. hatched areas are Environment Agency surveys) ..... 13
Table 5 Recommended DRA actions for Fowey sub catchments ......................................................... 21
Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Executive Summary
This is the ninth year in which Westcountry Rivers Trust (WRT) have carried out a catchment wide
electrofishing report on the River Fowey. The results of the 2020 survey have shown an improvement
on some of those from previous years and overall the catchment has performed well. The Water For
Growth project (W4G) continues work within the catchment for improvements to fish passage and
riparian and in-river habitat works. With the project entering its final year some of the information
from these surveys will be used to guide efforts and work within the catchment.
1. Introduction
WRT has undertaken semi-quantitative fry index electrofishing surveys throughout the River Fowey
as part of its annual monitoring program. This was the fourth year of catchment wide monitoring by
WRT which commenced as part of the monitoring for the W4G but the tenth consecutive year where
previous surveys were enabled by donations from Fowey Rivers Association (FRA).
Due to the global pandemic that is affecting many organisations WRT have had to adapt to a modified,
operator safeguarding survey methodology which was incorporated into this year’s fry index surveys.
Surveys were undertaken between June and September 2020 and a total of seven sites were
electrofished by WRT on the Fowey. Surveys were identified to allow for catchment wide coverage
with monitoring based on sites historically fished by the Environment Agency with older data available
for comparison, those where W4G outputs required monitoring and locations requested from local
angling interests.
1.1 Electrofishing Protocols
Electrofishing uses a controlled electric current to induce fish to swim toward an anode and into a
hand net, and thereby be counted and assessed. When carried out correctly by experienced and
qualified surveyors it is not harmful to fish and the fish are released back to the same location they
were caught. In upland streams and shallower sections of rivers, an electrofishing backpack is used
and therefore this type of kit was used for all the Fowey surveys.
There are several approaches to electrofishing assessments in rivers; quantitative, area semi-
quantitative and time semi-quantitative methodologies. All three methods have their advantages and
disadvantages.
Quantitative electrofishing is a thorough methodology that has the highest degree of accuracy of all
the methods. The main disadvantages of this approach are it is less mobile than backpack equipment
1Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
and it takes longer to undertake surveys. It Is therefore more costly than other approaches. With this
method, an area of river is netted off and the fish are removed from this defined stretch in multiple
passes until sufficient fish are removed to form a very accurate assessment of species and numbers.
It is not required to remove all the fish from the area but rather ensure a consistent fishing method
that gives a linear decrease in the number of fish caught per pass. The overall catch decline gives an
accurate estimate of the total number of fish in the location. This is known as the ‘depletion’
methodology.
An area-based semi-quantitative electrofishing methodology follows the same process as
quantitative electrofishing but only a single pass is carried out. A lack of multiple passes renders the
method only semi quantitative and therefore less accurate, but it has the advantage of being much
quicker than the depletion method, and it is suitable for use on all waterbody types. It is able to detect
multiple species and is reasonably accurate but is less time efficient and therefore costlier than a time-
based methodology (described below).
A time-based, semi-quantitative electrofishing methodology differs from both the approaches
described above. Instead of limiting the area fished (by use of nets) it limits the amount of time used
to fish to assess fish numbers. As no nets are deployed, fish in deeper sections of large rivers can
frequently avoid capture using this method. It is therefore only suitable to assess salmonid fry, who
are restricted to a shallower section of upland streams and rivers. This method is extremely rapid and
therefore cost-effective, allowing for deployment across whole river catchments although its major
drawback is its lower accuracy than netted approaches.
In weighing up the pros and cons of the various approaches it is worth considering what would be
required for a truly reliable method. In scientific publications it is usually considered that if an
approach is accurate 95% of the time then this is an acceptable standard. Such an approach would be
said to have sufficient statistical power to answer the question asked, for example, ‘has this habitat
improvement resulted in more fish in the area studied?’. For an electrofishing methodology to have
sufficient statistical power it requires a large number of sites to be fished in a fully-quantitative
depletion methodology over a number of years. As such an effort is rarely practicable and will cost
more than the habitat improvements it attempts to measure, this approach is rarely applied in the UK.
River managers in the UK have limited budgets and therefore it is the case that an electrofishing
programme of insufficient statistical power to achieve 95% confidence is usually accepted as a
compromise between accuracy and cost.
Bearing in mind the limits of statistical power that these approaches usually have (as practically
applied), it is important to consider the aim of a given electrofishing programme. In the case of WRT’s
2Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
catchment scale electrofishing programme, the aim is to build up historical data on each catchment
to provide information as to how to best take action to improve the fish stocks for salmon and trout.
To achieve this, the largest number of sites possible for maximum catchment coverage must be fished
over several consecutive years to i) guide current/future conservation strategies and ii) identify
whether or not the actions taken on the catchment have had a positive effect on fish numbers. Most
importantly the electrofishing programme is specified to be carried out at a catchment scale where
salmon and trout spawning areas occur. As most rivers have many tributaries or main stems of
considerable length, a relatively large number of sites are required for full coverage. This typically
equates to between 20 to 100 sites on rivers in southwest England, depending on the river catchment
geography. All things considered; a timed semi-quantitative approach was considered most
appropriate for the WRT electrofishing programme. This method will indicate the main issues and
areas that need addressing on a river catchment including:
• Upstream barriers to fish-passage
• Degraded habitat quality
• The upper limit of salmon spawning
• Successfully/Unsuccessfully enhanced habitat
• Catchment-scale fry migration due to river levels
• Point source and diffuse pollution
1.2 Life cycle and bottlenecks
The aim of the semi-quantitative electrofishing program is to identify issues that prevent salmonids
from effectively completing their life-cycle, and then proposing solutions that are proportionate to
the issue at hand. It is useful to adopt certain conceptual frameworks to each of these aims, and in
this report, we will use two of these frameworks; the ‘habitat bottlenecks’ that describe the causes
of issues in salmonid ecology (figure 1), and the ‘Defend/Repair/Restore’ conservation strategy
framework which describes the appropriate habitat action depending on the ecological situation
found at the site.
3Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Figure 1 Diagrams defining salmonid habitat bottlenecks (Summers et al, 1996)
1.3 Catchment Based Fisheries Conservation Strategy (Defend/Repair/Attack)
In using the fry index classification, catchment population abundance monitoring and determining the
river reach density classification, a series of priority areas can be outlined, and management
recommendations made tailored to the particular species. Recommendation actions broadly follow
the Defend/Repair/Attack concept, developed by Ronald Campbell of the Tweed Foundation. For
every river reach that is classified, a management action can be loosely determined.
Whilst this provides a useful structuring framework, the reality of given situations can bring many
complexities and lies on a continuum between these extremes. The goal is to move the river reaches
of the Fowey up from the unstable point (i.e. poor fish stocks and habitat) to the broad top of a
healthy, natural riverine ecosystem. Where the populations are in a very poor state, radical actions
may be required to see a change. Conversely, where the stocks are already good, habitat re-
engineering and stocking operations would be inappropriate. Actions to achieve these improvements
can be divided between ‘fish stock actions’ such as fish translocations or bag limits for anglers and
‘fish habitat actions’ such as removing barriers to migration or coppicing. In many situations, both
types of action will be required. This concept helps divide catchment scale management for fisheries
into priorities and therefore can help to maximise multiple benefits through targeted work.
2. Site selection
Sites were selected based on previous surveys to maintain monitoring consistency throughout the
catchment with a few additions incorporated to aid with the monitoring of works carried out under
W4G. The W4G project was a three-year programme which was extended by one year, and then given
4Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
another two-year extension. The project aims to improve fish passage within the Camel and Fowey
catchments and improve the ecological diversity within the catchment utilising riparian habitat
management. This project has now been extended by a further two years. By managing the
light/shade regime on the river water temperature can be kept cool while letting light into riffle
reaches which can help instigate primary production and benefit juvenile salmonids. These works can
also create habitat and refuge for salmonids increasing survival rates within their first year of life. W4G
is now entering its final year before the commencement of the two year extension, the previous survey
data has helped guide our management options within the catchment but has also aided us in
highlighting issues and concerns within individual sub catchments.
3. Field Sampling and data analysis methods
Permissions for all sites were established before electrofishing surveys took place. Each site was
electro fished by a two or three-person team. The voltage of the unit was set at each site depending
on the water conductivity. The operatives fished continuously for a standard five minutes over suitable
fry habitat without the use of stop nets. The fishing area was variable, and the length of fishing time
was fixed. Fish were collected in a net and placed into a holding bucket before processing.
All salmonids were identified to species and fork length was measured and recorded. Numbers or
density estimates were recorded for all other species captured. Habitat features such as land use,
substrate type and shading were recorded at each site. Any fry that were missed or escaped during
electrofishing were assigned to either trout or salmon groups depending on the relative percentage
of each species already recorded at the site.
The results of the electrofishing survey are classified according to the methodology of Crozier and
Kennedy (1994), displayed in Table 1, with each site being given an equivalent density classification
compared to quantitative monitoring. This semi-quantitative methodology was designed by Crozier
and Kennedy for both salmon and trout. However, the results for trout need adjustments to consider
the difference in the regression line for trout and salmon as described by Crozier and Kennedy. This
issue is planned to be investigated during the 2019 survey season utilising results of multiple, fully
quantitative surveys on the Tamar Catchment undertaken by WRT. The data will be analysed and
adopted for trout results going forward once it has undergone robust scientific scrutiny.
5Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Table 1 Semi-quantitative abundance categories for salmon fry (Crozier & Kennedy, 1994)
Semi-quantitative Quantitative
Density Classification
(n/5min fishing) (n 100m∙2)
A (excellent) >23 >114.7
B (good) 11-23 69.1-114.6
C (fair) 5-10 41.1-69.0
D (poor) 1-4 0.1-41.0
E (absent) 0 0
Based on the lengths of fish captured during the survey fry were considered to be any individual that
measured up to 85mm for salmon and 95mm for trout. In the catchment there was a clear difference
between 0+ and 1+ age group and so an upper limit cut off point was determined from a length
frequency distribution shown in Figures 2 & 3 below.
Atlantic Salmon Length Distribution 2020
25
20
15
Frequency
10
5
0
Size (mm)
Figure 2 2020 Fowey Salmon Length Frequency Distribution.
6Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Brown trout length distribution 2020
30
25
20
Frequency
15
10
5
0
Size (mm)
Figure 3 2020 Fowey Trout Length Frequency Distribution.
4. Results and Discussion
This survey year had a reduced number of survey sites due to COVID-19 and therefore we should be
cautious in drawing conclusions from these results. Next year we will survey a normal number of sites;
however, the results from 2020 surveyed sites are discussed below. Weather and other general survey
conditions were relatively consistent during the 2020 survey season on the Fowey catchment with
most surveys being completed on dry days. Similar to 2019 the river levels during the survey season
in 2020 were quite low, with water temperature being around 18° on some watercourses. Therefore,
care was taken by the survey team to ensure minimal stress to fish during survey operations, and
surveying ceased if water temperatures were too high or fish health was considered to be at risk, in
line with Environment Agency guidance.
Table 2 Fowey Salmon & Trout Fry Classifications 2020.
Site name Tributary 2020 Salmon Class 2020 Trout Class
Milltown Cardinham Absent - 0 Good - 13
US Glynn Cardinham Poor - 3 Good - 19
Lampen Lane St Neot Absent - 0 Excellent - 25
Kitesnest Woods St Neot Poor - 1 Good - 14
Trengoffe Wood Warleggan Excellent - 67 Good - 15
Lewarne LDAC Fowey Poor - 2 Good - 13
Golitha Draynes Fowey Poor - 2 Poor - 4
7Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Figure 4 Total catch data for River Fowey, 2020
8Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Figure 5 Salmon and trout classifications River Fowey, 2020
9Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Salmon classification
River Site 2010 2011 2012 2013 2014 2015 2017 2018 2019 2020
Fowey Leskernick Hill E E E E E E E E
Fowey Blackhill Down E E E E E E
Fowey Dozmary Downs E E C D C E
Fowey Harrowbridge Hill C E D E E D C E B
Fowey Westerlake Farm D D D C D D D
Fowey u/s North Netherton Bridge B D D C B C D D B
Fowey Golitha Draynes B C C B D C B D B D
Fowey The Nether C C D C D D C C B
Fowey Ashford Bridge C A D C D C E D
Fowey Doublebois Bridge B A D B D B B A C
Fowey D/S Bodithial Bridge B D C B B D E B E
Fowey Lewarne LDAC New Site D C D
Fowey Rivermead B B C D B A C
Fowey U/S Newbridge B D B C C C C
Fowey Glynn U/S Parkway D C D D C C B
Fowey Respryn Bridge B A D B C C
Fowey Below WTW C B B D E E E
Fowey Restormel Farm B B B D D C E D D
Fowey Trib. Lower Langdon E
Fowey Trib. Bulland Downs E C E D E E
Fowey Trib. Bodithial Stream E E E E E E E E
Fowey Trib. Clinnick Viaduct E E E E E E E E
Fowey Trib. Cabilla Wood D D D E D D E D E
Fowey Trib. Drift Lane E E E E E E E
Fowey Trib. Golden Lake E E E E E E E E
10Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Trenant Stream Whitebarrow Downs E
Trenant Stream Wortha E E E E E
Trenant Stream Lower Trenant D D E D E E E
Trenant Stream Carpuan New for 2019 E
St. Neot East Colliford E E E E E D A
St. Neot Trewindle E E E E E E E E E
St. Neot u/s St. Neot B B E E E E E
St. Neot Lampen Lane E A E
St. Neot Carnglaze Caverns E D E E E E E E D
St. Neot Kitesnest Woods D C C E D D D A D
Warleggan River Temple New Bridge E E E E E E E E
Warleggan River Glynn Valley Works D
Warleggan River u/s Cabilla Tor C D
Warleggan River Carne Wood B C C C D E
Warleggan River Crabbshill Wood C B C C D B C E C
Warleggan River Trengoffe Wood C C B A
Warleggan River Holtroad Downs (between weirs) D D D D E B
Warleggan River Whiterail Bridge New for 2019 E
Warleggan Trib. Castle Dewey E E E E E E E
Warleggan Trib. Barleysplat Wood C C E E E
Cardinham Water Millpool E E E E E E E E
Cardinham Water Cardinham D E C E E E E
Cardinham Water Milltown E B E E
Cardinham Water Trib. Millpark D E D E E E E E
Cardinham Water Trib. Deviock Wood C B C E E E E E
Cardinham Water Callywith Wood Ford C B C E D E
Cardinham Water Fletchersbridge A B B B A E B D
11Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Cardinham Water U/S Glynn C A D D E B D D
Lerryn Collon Barton New for 2019 E
Table 3 Multi-year salmon fry classifications (N.B hatched areas are Environment Agency surveys).
12Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Trout classification
River Site 2010 2011 2012 2013 2014 2015 2017 2018 2019 2020
Fowey Leskernick Hill C B D A B C B B
Fowey Blackhill Down B C C B C D
Fowey Dozmary Downs A B C B B B
Fowey Harrowbridge Hill C B D C B B C B B
Fowey Westerlake Farm C C E D C B D
Fowey u/s North Netherton Bridge C D E E D C C D C
Fowey u/s North Netherton Weir C D E C D
Fowey Golitha Draynes C D D E C C D D B D
Fowey The Nether C D E D E B C D C
Fowey Ashford Bridge C D E D C D C C
Fowey Doublebois Bridge D D D E C D E E D
Fowey D/S Bodithial Bridge E D E D B A B B D
Fowey Lewarne LDAC New Site C D B
Fowey Rivermead D E D B B D D
Fowey U/S Newbridge D D D D B C B
Fowey Glynn U/S Parkway D E D C C B E
Fowey Respryn Bridge E D C C D C
Fowey Below WTW D E E D E D D
Fowey Restormel Farm D D E C C C D C D
Fowey Trib. Lower Langdon C
Fowey Trib. Bulland Downs B D B B B A
Fowey Trib. Bodithial Stream A B B A A A A C
Fowey Trib. Clinnick Viaduct B B A A A A A B
Fowey Trib. Cabilla Wood A B C D B B B B B
Fowey Trib. Drift Lane B B A B B A B
13Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Fowey Trib. Golden Lake B B A B A A B A
Trenant Stream Whitebarrow Downs C
Trenant Stream Wortha C C B B A
Trenant Stream Lower Trenant C C C C B C D
Trenant Stream Carpuan New for 2019 A
St. Neot East Colliford E E E E C C
St. Neot East Colliford E
St. Neot Trewindle D D E C C D D C B
St. Neot u/s St. Neot D D B B B A C
St. Neot Lampen Lane B C A
St. Neot Carnglaze Caverns C D B C B B C A B
St. Neot Kitesnest Woods C E B C B C B C B
Warleggan River Temple New Bridge A B B A B A A A
Warleggan River Glynn Valley Works B
Warleggan River u/s Cabilla Tor B B
Warleggan River Carne Wood B D C B D D
Warleggan River Crabbshill Wood D C D D C C B B B
Warleggan River Trengoffe Wood B A B B
Warleggan River Holtroad Downs (between weirs) C D D C C B
Warleggan River Whiterail Bridge New for 2019 A
Warleggan Trib. Castle Dewey C D B B B B A
Warleggan Trib. Barleysplat Wood B C A B A
Cardinham Water Millpool A A A B B D B A
Cardinham Water Cardinham B B C C B A A
Cardinham Water Milltown B A A B
Cardinham Water Trib. Millpark B C A B A A A A
Cardinham Water Trib. Deviock Wood A B A A A B A B
Cardinham Water Callywith Wood Ford D C C C D D
Cardinham Water Fletchersbridge D D C C B B C B
14Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Cardinham Water Fletchersbridge C
Cardinham Water U/S Glynn D B B C C C C B
Lerryn Collon Barton New for 2019 D
Table 4 Multi-year trout fry classification (N.B. hatched areas are Environment Agency surveys)
15Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Fowey Trout Fry Classification Stacks
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
2010 2011 2012 2013 2014 2015 2017 2018 2019 2020
Absent Poor Fair Good Excellent
Figure 6 Fowey trout fry classification stacks.
Fowey Salmon Fry Classification Stacks
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
2010 2011 2012 2013 2014 2015 2017 2018 2019 2020
Absent Poor Fair Good Excellent
Figure 7 Fowey salmon fry classification stacks
16Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Fowey salmon, trout & combined salmonid fry average numbers per
site surveyed.
30
25
Frequency
20
15
10
5
0
2011 2012 2013 2014 2015 2017 2018 2019 2020
Salmon 6 4 6 2 3 3 6 7 11
Trout 8 7 10 14 12 13 18 17 15
Combined 15 11 16 16 16 16 23 24 26
Salmon Trout Combined
Figure 8 Multi-year average fry numbers for salmon, trout and combined salmonids.
In 2020, the River Fowey salmonid survey assessed seven sites and showed similar numbers in
salmonid population to those of 2019, with some sites showing slightly increased fish densities and
some slightly decreased fish densities. Given the reduction in sample size, densities look similar but a
drop in resolution of the data has been caused by a smaller sample size. This does generate an idea of
how this year has performed but does not enable a good understanding of how the rest of the
catchment is performing due to only six survey sites being surveyed this year. Golitha Draynes and
Lewarne decreased in density with both sites scoring a poor for salmon fry.
Trout fry followed the same trend as trout in that the resolution of data has been reduced due to the
small sample size. In comparison, trout had increased at one site and decreased at another. Lewarne
scored good and was its highest scoring year for trout since surveys started at this site. Golitha Draynes
scored good for trout in 2019 but decreased to a poor in 2020 and although this is a decrease, historical
data suggests that this site usually performs between poor and fair.
Salmon classifications at Lampen Lane and Kitesnest Woods on the St Neot scored absent and poor
respectively and although both sites scored an excellent last year this year’s classifications follow the
same trend as previous years. It has been noted that last years sharp spike in salmon density was
highly likely caused by local stocking Lampen Lane scored an excellent for trout which is its highest
17Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
classification since surveying started at this site and Kitesnest Woods scored good which has improved
from last year’s fair classification.
Salmon classifications at Milltown and U/S Glynn on the Cardinham scored absent and poor
respectively which is the same classification it received in last years surveys and in previous years. U/S
Glynn has historically varied in salmon densities throughout eight years of surveying, in which time, it
has received absent, poor, fair, good and excellent classifications which have made it difficult to
observe any trends in the data. Additionally, the reduction in number of sample sites had made it
difficult to determine if this is a real effect, or if it is the result of fish moving in the sub-catchment,
away from the sites sampled. Such fish movements can be caused by changes in water levels and
other ecological variablles. Both sites scored good for trout which was a slight decrease for Milltown
which scored excellent last year but was an increase for U/S Glynn which has scored fair for the last
four years of surveying.
Trengoffe Wood was the only site that was surveyed on the Warleggan in 2020. This was the first year
this site has scored an excellent classification for salmon which consisted of 67 salmon fry, which is
almost three times the excellent threshold. More so, this is the first time a survey site has scored an
excellent classification for salmon on the Warleggan since WRT Fowey surveying records started in
2010. It also scored a good for trout which is consistent with historical data. The steady increase in
salmon densities could potentially be attributed to the ongoing habitat improvement works carried
out by WRT through the W4G project. 2021 electrofishing results will help determine if this is the
case.
The Fowey tributaries remain very important and high-quality habitats for supporting large numbers
of juvenile salmon and trout, although with slight reductions in overall quantities of fish recorded in
2020. The line graph (figure 8) was constructed using the average numbers of salmon, trout and
combined salmonids caught between 2011-2020. Since ten years of monitoring and data has been
collected some trends can now be observed. The graph is starting to show an overall upward trend
for average numbers of salmon, trout and combined salmonids. However, 2020 should be viewed with
some caution due to the low number of sies surveyed that year.
WRT will aim to continue its various habitat and other improvement works throughout the Fowey
catchment in the future, and endeavour to continue working with the local angling groups and other
18Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
interested stakeholders to maintain, manage and improve both the aquatic and terrestrial habitats
within the Fowey catchment.
5. Recommendations
Although the EF surveys are undertaken for recruitment of salmon and trout, they have slightly
different habitat preferences and one species will often dominate where the other has limited or no
presence. Therefore, management strategies need to be considered for each species, hence a
conservation strategy for both salmon and trout.
The strategy for restoration and conservation of sites suggested here broadly follows the “Defend,
Repair, Attack” (DRA) concept developed by Ronald Campbell of the Tweed foundation, and has, in
the past, been applied locally in the Exe catchment by the River Exe and Tributaries Association
project. The fry productivity of the rivers is assessed by a combination of historic semi-quantitative
electrofishing results, along with EA netted electrofishing sites added to this report at a later date.
These results are then applied in context of existing plans (e.g. Salmon Action Plan, habitat walkover
surveys and genetic data) to produce assessments and recommendations for each sub-catchment of
the river. These sub-catchments are classified according to three levels: Defend, Repair, and Attack.
Despite the DRA strategy being a useful tool to identify and prioritise works in catchments, the
requirements of waterbodies can rarely be quite so clear cut. The coloured arrow in table 5 represents
the continuum of the three strategies and the goal for each waterbody; to move all the Avon sites
from their current position to somewhere in the Defend category, or to ensure they remain in this
status if fish stocks are already good.
To begin to restore and/or maintain fry habitat in the Fowey catchment, WRT recommend the
following works:
Fencing: Riparian zones identified as receiving significant livestock access, with apparent
habitat degradation, should be fenced to limit trampling and bank side poaching. Precautions
should be taken to ensure livestock can access drinking water supply. Effective buffer strips
dependant on site characteristics is advised.
Coppicing: Targeted selective coppicing of woodland and abandoned riparian coppice
adjacent to juvenile habitat riffles should be undertaken. This will increase primary
productivity and food source for juvenile fish. Shade should be maintained on deeper pools
and runs for water temperature and adult fish habitat cover.
Gravel Cleaning: Key areas of high spawning potential have been identified, however high
sediment loads impact viability and survival. Whilst continued efforts are underway to
influence policy and land management practices, selective gravel cleaning should be carried
out to ensure available spawning habitat for the coming season.
19Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Erosion Control: Fencing and effective marginal habitat management will reduce erosion.
However, where specific areas of high pressure and vulnerability are identified, erosion
protection measures such as woody debris installation, environmentally sensitive revetments,
and strategic tree planting would be advantageous.
Fish Passage Assessment: Assessment of potential fish migration barriers using the Coarse
Resolution Rapid Assessment technique developed by the Scottish and Northern Irish Forum
For Environmental Research (SNIFFER). A standardised survey technique to assess porosity of
in-channel structures.
Farm Advice: A key management strategy for the protection and enhancement of riverine
systems. Approaching and working with local agricultural businesses to offer guidance on best
environmental practice, and the use of grants for application of the recommended actions
outlined.
In-Channel Habitat Restoration: Installation and construction of habitat enhancing features,
including woody debris introduction, flow manipulation with groins and kickers, bank
reprofiling for marginal zonation, strategic tree planting, gravel introduction and riffle
creation, and historic channel restoration. Advanced management usually applied post
success of other recommended actions.
Walkover Surveys: Recording of habitat availability relating to ontogenetic stages of fish,
including observed local land use and factors negatively impacting habitat quality. Often the
starting point for work in an area, this is an important component of catchment management.
Walkovers essentially build large scale understanding of a catchment and allow forging of
relationships with local land owners.
Interpretation: Sensitive spawning sites can be exposed to disturbance at key times of year.
Interpretation can be used to inform of salmonid presence and advise on in river site
avoidance.
Increase monitoring effort: some sites are very difficult to access and therefore are not
surveyed. By increasing survey effort, more information on whole catchment performance
can be achieved and allow for increase appropriate action. Increased surveys could include
red counts, invertebrate monitoring e.g. Riverfly and citizen science programmes that are run
by WRT.
20Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
Action
Fish In-channel Increase
Gravel Gravel Erosion Farm Walkover
Sub catchment Fencing Coppicing Passage Habitat Interpretation Monitoring
Cleaning augmentation Control Advice Surveys
Assessment Restoration Effort
Cardinham Water
Colliford Lake
Fowey (Upper)
Fowey (Warleggan to St
Neot)
Lerryn River
Lower River Fowey
St Neot River
Warleggan River
Table 5 Recommended DRA actions for Fowey sub catchments
21Westcountry Rivers Trust Electrofishing Survey Report - River Fowey, 2020
6. Acknowledgments
Thanks to all landowners who gave us permission to undertake surveys on the River Fowey catchment
during the hard times of the recent pandemic. We would also like to thank the FRA, and the
Environment Agency.
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