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LOUGHS AGENCY OF THE FOYLE CARLINGFORD AND IRISH LIGHTS COMMISSION

Stillwater Status Report: Lough Finn Stillwater Fish Stock Survey Loughs Agency of the Foyle Carlingford and Irish Lights Commission Art Niven, Jayne Colgan and Fearghail Armstrong December 2017

A lake fish stock assessment was conducted to record indicative species composition and abundance of Lough Finn, Co. Donegal during the Autumn of 2017.

Headquarters 22, Victoria Road Derry~Londonderry BT47 2AB Northern Ireland Tel: +44(0)28 71 342100 Fax: +44(0)28 71 342720 general@loughs-agency.org www.loughs-agency.org

Regional Office Dundalk Street Carlingford Co Louth Republic of Ireland Tel+353(0)42 938 3888 Fax+353(0)42 938 3888 carlingford@loughs-agency.org www.loughs-agency.org

Report Reference LA/Lake/09/17 CITATION: Niven, A.J., Colgan J. & Armstrong, F. (2017) Stillwater Status Report: Lough Finn, Co. Donegal. Loughs Agency, 22, Victoria Road, Derry~Londonderry Page 2 of 33

DOCUMENT CONTROL

Name of Document

Stillwater Status Report: Lough Finn

Author (s):

Art Niven, Jayne Colgan and Fearghail Armstrong

Authorised Officer:

John McCartney

Description of Content:

Stillwater Fish Stock Assessment

Approved by:

John McCartney

Date of Approval:

December 2017

Assigned review period:

5 Years

Date of next review:

September 2022

Document Code

LA/LAKE/09/17

This documents comprises

TOC

Text List of tables Table of Figures

No. Appendices

Version Control Table Version No.

Status Draft

Version 1

Author (s)

Reviewed by

Art Niven, John Jayne Colgan McCartney & Fearghail Armstrong

Approved by

Date of issue

John McCartney

December 2017

Version 2 Version 3

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TABLE OF CONTENTS

TABLE OF CONTENTS ......................................................................................... 4 ACKNOWLEDGEMENTS ...................................................................................... 7 PROJECT STAFF 2017.......................................................................................... 7 EXECUTIVE SUMMARY ....................................................................................... 8 1.0

INTRODUCTION ...................................................................................... 10 Fig 1. Stillwater Fish Survey being carried out on Lough Finn, 2017. ........ 10

2.0

BATHYMETRY SURVEY ............................................................................ 11 Fig 2 . Lough Finn survey underway ......................................................... 11 Fig 3. Bathymetry map of Lough Finn, Co Donegal ................................... 12

3.0

METHODS ............................................................................................... 13 Table 1. Details of survey nets deployed on Lough Finn survey. ............... 13 Fig 5. Nets being prepared before being deployed on Lough Finn............ 13 Fig 6. Lough Finn ...................................................................................... 14 Fig 7. Lough Finn bathymetry map with 50m x 50m grid sqares ............. 15 Fig 8. Net locations ................................................................................... 16

4.0

RESULTS .................................................................................................. 17

4.1

SPECIES RICHNESS ............................................................................ 17

Table 2. Number of each species captured by each gear type during the survey of Lough Finn, 2017. ..................................................................... 17 4.2

FISH ABUNDANCE ............................................................................. 17

Table 3. Mean (± S.E.) CPUE and BPUE for all fish species recorded on Lough Finn, 2017. ............................................................................................... 18 Fig 9. Arctic charr and brown trout from Lough Finn ................................ 18 Fig 11. Mean BPUE for all fish species captured in Lough Finn, 2017. ...... 19 4.3

BROWN TROUT STOCK DENSITY & POPULATION STRUCTURE .......... 20

Fig 12. Mean CPUE for all Brown Trout across sampled loughs ................ 21 Page 4 of 33

Fig 13. Mean BPUE for all Brown Trout captured across sampled loughs . 21 Fig 14. Length frequency Brown Trout, Lough Finn 2017 (N=146) ............ 22 Fig 15. Length weight relationship of Brown Trout, Lough Finn 2017 (n=146) ................................................................................................................. 22 4.4

ARCTIC CHARR STOCK DENSITY & POPULATION STRUCTURE............ 23

Fig 16. Mean CPUE for all Arctic Charr captured in Lough Fad East 2017 and Lough Finn (2017). ................................................................................... 23 Fig 17. Mean BPUE for all Arctic Charr captured in Lough Fad East 2017 and Lough Finn (2017). ................................................................................... 23 Fig 18. Length frequency of Arctic Charr, Lough Finn 2017 (n=27) ........... 24 Fig 19. Length weight relationship of Arctic Charr, Lough Finn 2017 ........ 24 4.6

EEL STOCK DENSITY AND POPULATION STRUCTURE ......................... 25

Fig 20. Mean CPUE for Eels, Lough Mourne 2010, Carn 2010, Lough Muck 2012, Nambraddan 2014, Camlough 2016, Enagh East 2016, Trusk 2016 and Lough Finn 2017. ...................................................................................... 25 Fig 21. Mean CPUE for Eels, Lough Mourne 2010, Carn 2010, Lough Muck 2012, Nambraddan 2014, Camlough 2016, Enagh East 2016, Trusk 2016 and Lough Finn 2017 ....................................................................................... 26 Fig 22. Length frequency for European Eel, Lough Finn 2017 (n=22) ........ 26 Fig 23. Length weight relationship of European Eel, Lough Finn 2017 (n=22) Table 4. Eel mean length and mean weight comparison for lakes surveyed 2010 – 2017. ............................................................................................ 27 4.5

FISH AGE AND GROWTH ................................................................... 28

Fig 24. Comparison growth curve showing back calculated length at age for Brown Trout, Lough Muck (2012), Lough Nambraddan (2014), Lough Trusk (2016), Lough Fad East (2017) and Lough Finn (2017). ............................. 28 Fig 25. Comparison growth curve showing back calculated length at age for Arctic charr, Lough Fad East (2017) and Lough Finn (2017). ..................... 29 Fig 26. Growth curve showing back calculated length at age comparing Brown Trout and Arctic Charr, Lough Finn (2017). ................................... 29 5.0

DISCUSSION ............................................................................................ 30 Page 5 of 33

6.0

INVASIVE SPECIES ................................................................................... 30

7.0

BIOSECURITY........................................................................................... 32

8.0

RECOMMENDATIONS ............................................................................. 32

9.0 REFERENCES ............................................................................................... 33

ACKNOWLEDGEMENTS The Loughs Agency sponsoring departments, board and staff are gratefully acknowledged for the funding, support and assistance provided to conduct stillwater fish stock assessments and status reporting in the Foyle and Carlingford areas. Land owners and angling associations are also gratefully acknowledged for their co-operation. PROJECT STAFF 2017 Fisheries Biologist/Project Manager

Art Niven

Fisheries Inspector/Coxswain

Roly Wysner

Assistant Scientific Officer

Jayne Colgan

Assistant Scientific Officer

Paul Doherty

Fisheries Intern

Fearghail Armstrong

GIS Manager

Marco Tognella/Joe McClelland

For further information contact art.niven@loughs-agency.org

@ArtNiven

Loughs Agency TV

Page 7 of 33

EXECUTIVE SUMMARY A Water Framework Directive compliant stillwater fish stock assessment was carried out on Lough Finn in September 2017. The Loughs Agency commenced a small rolling programme of lake fish surveys in 2010 to gain a better understanding of fish composition and abundance of the standing waterbodies within the Foyle and Carlingford areas. The information collected can be used for many purposes ranging from formal Water Framework Directive classification, a baseline survey for use in the scrutiny of any future development proposals and for contributing towards the sustainable development of the angling amenity. Lough Finn is situated in West Donegal approximately 25km West of Ballybofey and is the source of the River Finn. The lough is nestled at the base of the bluestack mountain range. Fintown lies on the Northern shore of Lough Finn. Previous baseline fisheries and Euopean eel scientific surveys have been conducted but did not follow Water Framework Directive compliant methods. Accurate depth (bathymetry) data was available to direct the fish survey. The 2017 fish stock assessment noted the presence of four fish species in Lough Finn including Brown trout, Arctic charr, European Eel and Minnow. Brown trout were the most common fish encountered in the survery. It is notable that a healthy population of Artic charr is present in the Lough. Water levels can fluctuate quite quickly on Lough Finn following periods of rainfall. This has been exacerbated in recent years by unauthorised drainage works which were conducted at the outflow from Lough Finn. Substrate was added to the outflow to mitigate the effects of the unauthorised dredging but the lowered bed level still appears to be having an impact upon water retention within Lough Finn and potentially upon the Lough Finn and River Finn fisheries. This lake survey report provides a baseline of species presence and their relative abundance to resource managers and anglers alike. It is anticipated that this survey report could contribute towards any future management and sustainable development of the angling amenity, conservation of the nationally vulnerable Arctic charr population and wider development of the lough by providing the basis for an evidence based approach to the management of the lough Page 8 of 33

If access to the Fish in Lakes 2 Water Framework Directive classification tool was available a WFD compliant classification could also be derived for Lough Finn and provided to the Environmental Protection Agency for national reporting purposes.

Page 9 of 33

1.0

INTRODUCTION

Lough Finn is located in West Donegal besdie the town of Fintown, in the Foyle catchment. The principal dimensions are; · · · ·

Length: 4.1km long Maximum width: 0.38 km Surface area: 115 hectares Maximum depth: 24 metres

Fig 1. Stillwater Fish Survey being carried out on Lough Finn, 2017.

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2.0

BATHYMETRY SURVEY

It is a prerequisite of any WFD compliant lake fish survey to have detailed bathymetry data, so that the survey can be carried out in accordance with the standard sampling methods for the assessment of ecological status in freshwater lakes across the island of Ireland (Eco-region 17). The area of the lake (ha) and the maximum depth (m) are used to determine the distribution and number of gill nets required for the survey. A bathymetery survey for Lough Finn had been previously completed prior to the lake fish survey. This information was used to direct the fish survey.

Fig 2 . Lough Finn survey underway

Page 11 of 33

Fig 3. Bathymetry map of Lough Finn, Co Donegal

3.0

METHODS

Nets on Lough Finn were set on the 12th of Spetember 2017 and left overnight and collected on 13th September according to the methodology described in the Water Framework Directive compliant NS Share Methods Manual for systematic surveying of lakes for fish (NSSHARE, 2008). A total of 31 nets were set as summarised in Table 1 below. Net type

No. Deployed

Water depth (m)

Dutch fyke nets (chain of 3) Multi-mesh gill nets

0 – 2.9

Multi-mesh gill nets

3 – 5.9

Multi-mesh gill nets

6 – 11.9

Multi-mesh gill nets

12 – 19.9

Multi-mesh gill nets

>20

Floating gill net

18-21

Table 1. Details of survey nets deployed on Lough Finn survey.

Fig 5. Nets being prepared before being deployed on Lough Finn.

Page 13 of 33

Survey locations were chosen within randomly selected 50m X 50m grid squares overlaid on a bathymetric map of the lough (Figure 3). The location and depth of each net is also shown in figure 4. A handheld Trimble Geo HT GPS was used to record the precise location of each net as shown in Figure 4 above. Any fish which were alive and in good condition were measured and released live after removal from the nets, this included all eels caught in fyke nets. All other fish were removed from the nets, identified and measured at Loughs Agency headquarters.

Fig 6. Lough Finn

Page 14 of 33

Fig 7. Lough Finn bathymetry map with 50m x 50m grid sqares

Page 15 of 33

Fig 8. Net locations

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4.0

RESULTS

4.1

SPECIES RICHNESS

A total of 4 fish species were recorded on Lough Finn in September 2017 with a total of 209 fish captured during the survey. A list of all species captured by each gear type is presented in Table 2. Arctic charr one of Irelands rarerest native fish species was recorded with 23 captured during this survey. Brown trout were the most common fish species encountered in the benthic gill nets. All eels apart from 1 were captured in the fyke nets. A total of 13 minnows were also captured.

Common Name

Scientific Name

Benthic Fyke Gill Nets Nets

Pelagic Gill Nets

Total

Brown trout Arctic Charr European Eel Minnow

Salmo trutta

138

146

Salvelinus alpinus Anguilla anguilla Phoxinus phoxinus

Table 2. Number of each species captured by each gear type during the survey of Lough Finn, 2017.

4.2

FISH ABUNDANCE

Fish abundance, mean catch per unit effort (CPUE) was calculated as the mean number of fish caught per metre of net. Fish biomass, mean biomass per unit effort (BPUE) was calculated as the mean weight of fish caught per metre of net. For all fish species CPUE/BPUE is based on all nets including fyke nets. Weights were not available from those fish which were released alive. In such cases weights were calculated from the length weight relationship of recorded fish. A summary of CPUE and BPUE data for each species is shown in Figure 10 and 11 below.

Page 17 of 33

Brown trout were the dominant fish species in terms of abundance and also in terms of biomass. Arctic Charr were much lower in terms of abundance and also in terms of biomass as shown below in Table 3. Common name Brown Trout

Scientific name Salmo trutta

2017 CPUE 0.157 (0.042)

2017 BPUE 11.741 (3.345)

Arctic Charr

Salvelinus alpinus

0.029 (0.010)

1.874 (0.620)

European Eel

Anguilla anguilla

0.122 (0.031)

15.767 (4.782)

Minnow

Phoxinus phoxinus

0.019 (0.009)

Table 3. Mean (± S.E.) CPUE and BPUE for all fish species recorded on Lough Finn, 2017.

Fig 9. Arctic charr and brown trout from Lough Finn

Page 18 of 33

0.250

CPUE (number of fish/m of net)

0.200

0.150

0.100

0.050

0.000 Brown Trout

Arctic Char

Eel

Minnow

Species

Fig 10. Mean CPUE for all fish species captured in Lough Finn, 2017. 25.000

BPUE (number of fish/m of net)

20.000

15.000

10.000

5.000

0.000 Brown Trout

Arctic Char

Eel

Minnow

Species

Fig 11. Mean BPUE for all fish species captured in Lough Finn, 2017.

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4.3

BROWN TROUT STOCK DENSITY & POPULATION STRUCTURE

The relative density (CPUE & BPUE) and length frequency distribution of Brown trout is presented below in Figures 12, 13, 14 & 15. Values are also compared with other lakes which have been surveyed within the Foyle and Carlingford areas. A total of 146 Brown trout were recorded during the Lough Finn survey, lengths ranged from 60mm to 299mm (mean length 186mm). The abundance of Brown trout in Lough Finn is significantly higher than many other surveyed loughs. Eight Brown trout were recorded in Lough Fad East (2017), lengths ranged from 170mm to 450mm (mean length 277mm). Forty four Brown trout were recorded in Lough Muck (Donegal) 2012, lengths ranged from 69mm to 212mm (mean length 168mm). Eighteen Brown trout were recorded in Lough Alaan 2013, lengths ranged from 134mm to 314mm (mean length 234mm). Three Brown trout were recorded in Lough Carn 2010, lengths ranged from 389mm to 422mm (mean length 406mm). Twenty five Brown trout were recorded in Lough Ash 2011, lengths ranged from 297mm to 421mm (mean length 343mm). Two Brown trout were recorded in Lough Mourne 2010, lengths ranged from 205mm to 220mm (mean length 213mm). Fifety nine Brown trout were recorded in Lough Nambradden 2014, lengths ranged from 55mm to 240mm (mean length 147mm).

Page 20 of 33

0.2

0.15

0.1

Trusk 2016

Fad 2017

Finn 2017

Fad 2017

Finn 2017

Alaan 2013

Muck 2012

Ash 2011

Carn 2010

Mourne 2010

Trusk 2016

0.05

Nambraddan 2014

CPUE (Number of fish/m net)

0.25

Site

Fig 12. Mean CPUE for all Brown Trout across sampled loughs 50

BPUE (Mean biomass (g) of fish/m net)

45 40 35 30 25 20 15 10

Alaan 2013

Muck 2012 (Donegal)

Ash 2011

Carn 2010

Mourne 2010

Site

Nambraddan 2014

Fig 13. Mean BPUE for all Brown Trout captured across sampled loughs

Page 21 of 33

Frequency

0-9 10 - 19 20 - 29 30 - 39 40 - 49 50 - 59 60 - 69 70 - 79 80 - 89 90 - 99 100 - 109 110 -119 120 - 129 130 - 139 140 - 149 150 -159 160 - 169 170 - 179 180 - 189 190 - 199 200 - 209 210 - 219 220 - 229 230- 239 240 - 249 250 - 259 260 - 269 270 - 279 280 - 289 290 - 299 300 - 309

Length (mm)

Fig 14. Length frequency Brown Trout, Lough Finn 2017 (N=146) 350 y = 3E-05x2.795 R² = 0.9178

300

Weight (g)

250

200

150

100

3.6

0 0

100

150

200

250

300

350

Length (mm)

Fig 15. Length weight relationship of Brown Trout, Lough Finn 2017 (n=146)

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4.4

ARCTIC CHARR STOCK DENSITY & POPULATION STRUCTURE

The relative density (CPUE & BPUE) and length frequency distribution of Arctic Charr is presented below in Figures 16, 17, 18 & 19. A total of 28 Arctic Charr were recorded in Lough Finn, lengths ranged from 60mm to 214mm (mean length 175mm). Values for Arctic Charr are compared with results from Lough Fad East which was also sampled in 2017 and contained Charr. 0.045

CPUE (Number of fish/m net)

0.040 0.035 0.030 0.025 0.020 0.015 0.010 0.005 0.000 Lough Fad 2017

Lough Finn 2017

Fig 16. Mean CPUE for all Arctic Charr captured in Lough Fad East 2017 and Lough Finn (2017).

Bpue (Mean biomass (g) of fish/m net

3.000

2.500

2.000

1.500

1.000

0.500

0.000 Lough Fad 2017

Lough Finn 2017

Fig 17. Mean BPUE for all Arctic Charr captured in Lough Fad East 2017 and Lough Finn (2017).

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10 9 8

Frequency

7 6 5 4 3 2 1 220-229

210 - 219

200 - 209

190 - 199

180 - 189

170 - 179

160 - 169

150 -159

140 - 149

130 - 139

120 - 129

110 -119

100 - 109

90 - 99

80 - 89

70 - 79

60 - 69

50 - 59

40 - 49

30 - 39

20 - 29

10 - 19

0-9

Length (mm)

Fig 18. Length frequency of Arctic Charr, Lough Finn 2017 (n=27)

140

y = 2E-06x3.3602 R² = 0.9617

120

Weight (g)

100

0 0

100

150

200

250

Length (mm)

Fig 19. Length weight relationship of Arctic Charr, Lough Finn 2017 (n=27)

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4.6

EEL STOCK DENSITY AND POPULATION STRUCTURE

The relative density (CPUE & BPUE) and length frequency distribution of Eels is presented below. A total of 23 Eels were recorded in Lough Finn, lengths ranged from 32.5cm – 53.5cm. Values are also compared with other lakes which have been surveyed within the Foyle and Carlingford areas. 0.5

CPUE (Number of fish/m net)

0.4

0.3

0.2

0.1

Lough Finn 2017

Trusk 2016

Enagh East 2016

Camlough 2016

Nambraddan 2014

Muck 2012 (Donegal)

Carn 2010

Mourne 2010

Site

Fig 20. Mean CPUE for Eels, Lough Mourne 2010, Carn 2010, Lough Muck 2012, Nambraddan 2014, Camlough 2016, Enagh East 2016, Trusk 2016 and Lough Finn 2017.

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540-549

520-529

500-509

480-489

460-469

440-449

420-429

400-409

380-389

360-369

340-349

320-329

Mourne 2010

Lough Finn 2017

Trusk 2016

Enagh East 2016

Camlough 2016

Nambraddan 2014

Muck 2012 (Donegal)

Carn 2010

Site

300 - 309

280 - 289

260 - 269

240 - 249

220 - 229

200 - 209

180 - 189

160 - 169

140 - 149

120 - 129

100 - 109

80 - 89

60 - 69

40 - 49

20 - 29

0-9

Frequency

BPUE (Mean biomass (g) of fish/m net)

200

175

150

125

100

Fig 21. Mean CPUE for Eels, Lough Mourne 2010, Carn 2010, Lough Muck 2012, Nambraddan

2014, Camlough 2016, Enagh East 2016, Trusk 2016 and Lough Finn 2017.

Length (mm)

Fig 22. Length frequency for European Eel, Lough Finn 2017 (n=22)

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350 y = 0.0016x3.0023 R² = 0.9642

300

Weight (g)

250

200

150

100

0 0

Length (cm)

Fig 23. Length weight relationship of European Eel, Lough Finn 2017 (n=22)

Lake Lough Mourne 2010 Lough Carn 2010 Lough Muck 2012 (Donegal) Nambraddan 2014 Camlough 2016

Number of Eels 13

Mean Length 465 mm

Mean Weight 231 g

605 mm

420 g

380 mm

123 g

409 mm

130 g

529 mm

764 g

Enagh Lough East 2016 Lough Trusk 2016 Lough Finn 2017

529 mm

720 g

442 mm

230 g

424mm

137g

Table 4. Eel mean length and mean weight comparison for lakes surveyed 2010 – 2017.

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4.5

FISH AGE AND GROWTH

Scales were taken from 77 Brown trout and 26 Arctic charr caught during this survey. A sub sample of 32 Brown trout scales and 15 Arctic charr scales were read for fish aging and back calculated growth analysis. Figure 23 below outlines the average length at age for Brown trout caught during the survey and compares them to Brown trout caught in Lough Muck (2012), Lough Nambraddan (2014), Lough Trusk (2016) and Lough Fad East (2017). A range of age classes were present in Lough Finn with the oldest Trout found to be in the 6+ age class. 50 Lough Muck 45 Lough Nambraddan 40 Lough Trusk 35

Lough Fad (East)

Length (cm)

Lough Finn

0 Length at age

Fig 24. Comparison growth curve showing back calculated length at age for Brown Trout, Lough Muck (2012), Lough Nambraddan (2014), Lough Trusk (2016), Lough Fad East (2017) and Lough Finn (2017).

Page 28 of 33

Figure 25 below shows the average length at age for Arctic Charr caught during the survey. The oldest Arctic charr was found to be in the 4+ age class. 18 16 14

Length (cm)

12 10 Lough Fad 8

Lough Finn

6 4 2 0 1

Length at age

Fig 25. Comparison growth curve showing back calculated length at age for Arctic charr, Lough Fad East (2017) and Lough Finn (2017). 30

Length (cm)

15 Brown Trout Arctic Charr

0 L1

Length at age

Fig 26. Growth curve showing back calculated length at age comparing Brown Trout and Arctic Charr, Lough Finn (2017).

Page 29 of 33

5.0

DISCUSSION

Additional information collected during survey but not reported on here includes water quality data on Dissolved Oxygen, pH, temperature, Total Phophorous and fish stomach content analysis. This information has been retained for future analysis if and when time and resources become available. Lough Finn is an extremely important lough. It holds a population of nationally rare Arctic charr which as evidenced during the 2017 survey had multiple cohorts present including young of the year. This population appears to be in reasonable condition but further assessment against favourable condition standards would need to be made in order to derive a formal condition assessment. The population of Brown trout and European eel also appears to be in reasonable condition. A large population of small Brown trout was recorded. No larger specimens were encountered during this survey and a general decline in larger Brown trout caught by local anglers was commented on by local contacts. Larger salmonids have been observed locally at the outflow to Lough Finn at spawning time. It is not known if these fish were Salmon or Trout. Lough Finn has a small geographical area draining into it and water levels historically where stable. The outflow was dredged a number of years ago and reinstated to a lower level. The reducytion in bed level at the outflow results in water levels running off the lough much faster than previously. This has added to the spate nature of the Finn catchment minimising the natural buffering caopacity offered by Lough Finn on both water chemistry and water levels. Arctic charr may be spawning in the littoral areas and any fluctuations in water levels at sensitive incubation periods have the potential to impact negatively on this population.

6.0

INVASIVE SPECIES

Invasive non-native species are those which have been transported outside of their natural range. They are capable of spreading rapidly and colonising a wide range of habitats. They also exhibit competitive dominance by out-competing Page 30 of 33

native flora and fauna for light, oxygen and food. There is growing evidence to suggest that invasive riparian plants are having an adverse effect on aquatic habitats and species by altering both in-stream processes and terrestrial-aquatic linkages. Invasive species threaten native species as direct predators or competitors, as vectors of disease, and by modifying the native habitats. Invasive species are considered the second biggest threat after habitat loss to biodiversity worldwide by the Millennium Ecosystem Assessment in 2005. Water is an excellent transport medium for the dispersion of many of these species. Rivers and loughs with their banks and shorelines are amongst the most vulnerable areas to their introduction, spread and impact. The focus for the Loughs Agency is predominantly on aquatic and riparian invasive species as these are a serious threat to our sensitive aquatic habitats. The spread of invasive species can also further threaten already endangered native species. In freshwater habitats the introduction of invasive species is considered the second leading cause of species extinctions. Invasive species are a global problem and once they are established eradication is often costly and extremely difficult. Previous studies suggest that early intervention is a more successful and cost-effective way of preventing the spread of invasive species. There are a multitude of invasive non-native species across the UK and Ireland at present, many of them with the potential to cause serious environmental harm. Three species in particular, Japanese Knotweed (Fallopia japonica), Himalayan Balsam (Impatiens grandulifera) and Giant Hogweed (Heracleum mantegazzianum) have become an established threat to the streams and rivers of the Foyle and Carlingford areas. Rivers are an excellent means of transporting, dispersing and spreading invasive species, therefore it is no great surprise to see a proliferation along our river corridors. There is a growing body of evidence demonstrating the damaging impacts of (INNS) invasive non-native species. The problem of excessive soil erosion along the riparian zone can have grave consequences for freshwater fish species. Atlantic salmon (Salmo salar) and Trout (Salmo trutta) are reliant upon finding appropriately sized spawning gravel to complete their life cycle. However, Himalayan Balsam will die back in winter time, leaving behind exposed river Page 31 of 33

banks devoid of any natural vegetation. The lack of vegetation on the riparian zone leaves the bank highly susceptible to soil erosion at times of increases flows and floods. Excessive soil erosion will increase the sediment load into the stream reach and can potentially smother the eggs buried in the spawning gravel, starving them of oxygen. Atlantic salmon stocks are at unprecedented low levels and they are also experiencing very high mortality rates during the marine phase of their life cycle. Increased sediment being introduced to rivers and streams has the potential to diminish juvenile abundance even further and merely exacerbates the problem still further. 7.0

BIOSECURITY

Good biosecurity exists on Lough Finn with boat launching access limited and controlled. A fleet of angling boats are available for rent minimising the pressure to transport boats from other areas which may host invasive species. Additional biosecurity measures should also be encouraged to prevent the spread of invasive non nantive species. Invasive species are an ever present threat in our aquatic and riparian systems and it is imperative that none of our field operations exacerbate the risks to the environment and to the economy that are posed by these species. Fish parasites, pathogens and diseases also represent a significant threat to the health status of our watercourses. The introduction or transfer of such pathogens or diseases has the potential to wipe out large populations of fish in affected waters or catchments. Loughs Agency staff are required to be vigilant to help prevent the spread of fish diseases and invasive species. The agency has incorporated biosecurity protocols into its freshwater fisheries monitoring programme and these guidelines are also adhered to by fishery officers and field staff alike. The Loughs Agency biosecurity protocol for field operations was fully implemented during the Lough Finn fish survey. 8.0

RECOMMENDATIONS · Repeat survey every 5 years. · Conduct fisheries assessments on the inflowing tributaries to Lough Finn Page 32 of 33

· Conduct spawning survey/camera deployment/trapping exercise at the outflow to Lough Finn at spawning time · Investigate the potential for raising the outflow to Lough Finn to align with original bed levels. · Compare results against any future surveys in the Foyle area to ascertain comparative growth rates across and within a range of stillwaters of the Foyle and Carlingford areas. · Communicate findings internally to colleagues and externally to stakeholders · Continue to conduct stillwater fish surveys temporally and spatially within the Foyle and Carlingford areas. · Promote Biosecurity awareness with angling community · Liaise with angling associations to develop best practice management advice

9.0 REFERENCES Kelly, FL (2008) WFD Surveillance Monitoring Fish in Lakes (2007) Central and Regional Fisheries Board report. Kelly, F.L., Connor, L., Wightman, G., Matson, R., Morrissey, E O’Callaghan, R., Feeney, R., Hanna, G. and Rocks, K., (2009) Sampling fish for the Water Framework Directive – Summary Report 2008. Central and Regional Fisheries Board report. North South Share Aquatic Resource (NS Share). Methods Manual V Fish (2008) European CEN Standard. Water quality-Sampling of fish with multi-mesh gill nets (2005). Page 33 of 33