Stillwater Status Report: Lough Muck, County Donegal

Transcription

1 LOUGHS AGENCY OF THE FOYLE CARLINGFORD AND IRISH LIGHTS COMMISSION Stillwater Status Report: Lough Muck, County Donegal Stillwater Fish Stock Survey Loughs Agency of the Foyle Carlingford and Irish Lights Commission Art Niven & Mark McCauley A lake fish stock assessment was conducted to record indicative species composition and abundance of Lough Muck, County Donegal during the summer of 2012.

2 Headquarters 22, Victoria Road Derry~Londonderry BT47 2AB Northern Ireland Tel: +44(0) Fax: +44(0) g e n e r a l o u g h s - a g e n c y. o r g w w w. l o u g h s - a g e n c y. o r g Regional Office Dundalk Street Carlingford Co Louth Republic of Ireland Tel+353(0) Fax+353(0) c a r l i n g f o r l o u g h s - a g e n c y. o r g w w w. l o u g h s - a g e n c y. o r g Report Reference LA/Lake/0?/12 CITATION: Niven, A.J. & McCauley, M. (2015) Stillwater Status Report: Lough Muck, County Donegal. Loughs Agency, 22, Victoria Road, Derry~Londonderry Page 2 of 21 [Type a quote

3 DOCUMENT CONTROL Name of Document Stillwater Status Report: Lough Muck, County Donegal Author (s): Art Niven & Mark McCauley Authorised Officer: John McCartney Description of Content: Approved by: Stillwater Fish Stock Assessment John Pollock Date of Approval: June 2015 Assigned review period: 5 Years Date of next review: June 2015 Document Code This documents comprises LA/LAKE/09/12 TOC Text List of tables Table of Figures X X X X No. Appendices Version Control Table Version No. Status Author (s) Reviewed by Approved by Date of issue Version 1 Draft Art Niven John McCartney John Pollock 30/06/2015 Revision 2 Revision 3 Version 3 Page 3 of 21

4 TABLE OF CONTENTS TABLE OF CONTENTS... 4 ACKNOWLEDGEMENTS... 6 PROJECT STAFF EXECUTIVE SUMMARY INTRODUCTION... 8 Fig 1 Lough Muck (Donegal) METHODS... 9 Fig 2. Details of survey nets deployed... 9 Fig.3 Fyke net being deployed and water sampling on Lough Muck (Donegal) Fig.4 Lough Muck (Donegal) net locations Fig.5 Lough Muck (Donegal) 50 metre grids RESULTS SPECIES RICHNESS Fig.7 Number of each fish species captured by each gear type during the survey of Lough Muck (Donegal) Fig 8. European eels from Lough Muck, Co Doengal FISH ABUNDANCE Fig 9. Mean (± S.E.) CPUE and BPUE for all fish species recorded on Lough Muck (Donegal) LENGTH FREQUENCY DISTRIBUTION Fig.15 Lough Muck (Donegal) Fig.16 Length frequency Trout, Lough Muck 2012 (N=44) Fig.17 Length frequency Eel, Lough Muck 2012 (N=10) FISH AGE AND GROWTH Page 4 of 21

5 Fig 18. Trout growth back calculated growth rates for Brown trout caught in Lough Muck Co Donegal 2012 n = DISCUSSION RECOMMENDATIONS REFERENCES This document and its contents are copyright of the Loughs Agency 2015 Page 5 of 21

6 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 2012 Fisheries Biologist/Project Manager GIS Officer Assistant Scientific Officer Assistant Scientific Officer Fisheries Intern Fisheries Intern Art Niven Rachel Scott Mark McCauley Simon Guist Luke Murphy Sylvain Poral For further information Loughs Agency TV LOUGHS AGENCY OF THE FOYLE CARLINGFORD AND IRISH LIGHTS COMMISSION 2015 Page 6 of 21

7 EXECUTIVE SUMMARY A Water Framework Directive compliant stillwater fish stock assessment was carried out on Lough Muck, Co Donegal in August 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, baseline survey for use in the scrutiny of any future proposals and for contributing towards the sustainable development of the angling amenity. Lough Muck, Co Donegal was selected for survey on the basis that anecdotal evidence suggested that there was a reasonable population of small Brown trout. The Lough is also freely connected to the Stranagoppogue River a tributary of the River Finn. There was the possibility of access to Lough Muck by migratory salmonids including Sea trout and Atlantic salmon. The nearby Lough Finn also holds a population of Arctic char and it was decided that for these combined reasons and due to its high potential amenity value that a baseline fish survey should be conducted. The 2012 fish stock assessment noted the presence of two fish species in Lough Muck, Co Donegal, Brown trout and European eel with a total of 54 individual fish captured during the survey. Brown trout were the most common fish species encountered. It is anticipated that this survey report could significantly contribute towards the future sustainable development of angling initiatives, infrastructure and development plans for Lough Muck, Co Doengal through highlighting the species and their relative abundance to fishery managers. Potential exists for a wellmanaged fishery to be maintained by the owner of the fishing rights. 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 Mourne and provided to the Environment Protection Agency for national reporting purposes. Page 7 of 21

8 1.0 INTRODUCTION Lough Muck is located approximately 8km south-west of Ballybofey, Co. Donegal in the Finn catchment. The lake is located at an altitude of metres above sea level and its principal dimensions are; Length: 1.9km long, maximum width 560 metres Surface area: 27 hectares Mean depth: 4.3 metres, maximum depth: 12.5 metres Fig 1 Lough Muck (Donegal) Page 8 of 21

9 2.0 METHODS Lough Muck, Co Donegal was surveyed over one night on the 9 th of August 2012 according to the methodology described in the Water Framework Directive compliant NS Share Methods Manual for systematic surveying of lakes for fish (NSSHARE, 2008). Prior to the commencement of the fish survey a bathymetric survey was conducted to obtain accurate depth data. A total of 12 nets were set as summarised in Figure 2. Net type No. Deployed Water depth (m) Dutch fyke nets (chain of 3) Multi-mesh gill nets Multi-mesh gill nets Multi-mesh gill nets Floating gill nets Fig 2. Details of survey nets deployed Survey locations were chosen within randomly selected 50m X 50m grid squares overlaid on a bathymetric map of the lough. A handheld Trimble Geo HT GPS was used to record the precise location of each net. The location and depth of each net is shown in Figure 4. Any fish which were alive and in good condition were measured and released live after removal from the nets, this included all eels. All other fish were removed from the nets and identified and measured on site. Page 9 of 21

10 Fig.3 Fyke net being deployed and water sampling on Lough Muck (Donegal) 2012 Page 10 of 21

11 Fig.4 Lough Muck (Donegal) net locations Page 11 of 21

12 Fig.5 Lough Muck (Donegal) 50 metre grids Page 12 of 21

13 3.0 RESULTS 3.1 SPECIES RICHNESS A total of two fish species were recorded on Lough Muck in August 2012 with a total of 54 fish captured during the survey. A list of species encountered and captured by each gear type is compiled in Figure 7. Brown trout were the most common fish species encountered in the benthic gill nets. Eels were captured in the fyke nets. Common Scientific Benthic Surface gill Fyke nets Total name name gill nets nets Brown Salmo trout trutta Eel Anguilla anguilla Fig.7 Number of each fish species captured by each gear type during the survey of Lough Muck (Donegal) 2012 Fig 8. European eels from Lough Muck, Co Doengal Page 13 of 21

14 3.2 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 except eel, CPUE/BPUE is based on all nets including fyke nets, whereas eel CPUE/BPUE is based on fyke nets only. 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 9. Brown trout were the dominant fish species in terms of abundance and eels were the dominant species in term of biomass. Common name Scientific name 2012 CPUE 2012 BPUE Brown trout Salmo trutta (0.057) (3.448) Eel Anguilla anguilla (0.111) (4.357) Fig 9. Mean (± S.E.) CPUE and BPUE for all fish species recorded on Lough Muck (Donegal) Fig 10. Brown trout caught in benthic gill net, Lough Muck, Co Donegal 2012 Page 14 of 21

15 0.3 CPUE (Number of fish/m net) Trout Species Fig 11. Mean (± S.E.) CPUE for all fish species captured in Lough Muck 2012 (Eel CPUE based on Fyke nets only). Eel 21 Mean BPUE Lough Muck, 2012 BPUE (Mean biomass (g) of fish/m net) Trout Species Fig 12. Mean (± S.E.) BPUE for all fish species captured in Lough Muck 2012 (Eel BPUE based on Fyke nets only). Eel Page 15 of 21

16 CPUE (Number of fish/m net) Lough Mourne 2010 Lough Carn 2010 Lough Ash 2011 Lough Muck 2012 Site Fig 13. Mean CPUE for all Brown trout captured in Lough Mourne 2010, Lough Carn 2010, Lough Ash 2011 and Lough Muck BPUE (Mean biomass (g) of fish/m net) Lough Mourne 2010 Lough Carn 2010 Lough Ash 2011 Lough Muck 2012 Site Fig 14. Mean BPUE for all Brown trout captured in Lough Mourne 2010, Lough Carn 2010, Lough Ash 2011 and Lough Muck Page 16 of 21

17 CPUE (Number of fish/m net) Lough Mourne 2010 Lough Carn 2010 Lough Muck 2012 Site Fig 15. Mean CPUE for all Eels captured in Lough Mourne 2010, Lough Carn 2010 and Lough Muck BPUE (Mean biomass (g) of fish/m net) Lough Mourne 2010 Lough Carn 2010 Lough Muck 2012 Site Fig 16. Mean BPUE for all Eels captured in Lough Mourne 2010, Lough Carn 2010 and Lough Muck Page 17 of 21

18 3.3 LENGTH FREQUENCY DISTRIBUTION A total of 44 Brown trout were captured during the 2012 survey. Trout lengths ranged from 6.9cm to 21.2cm (mean length 16.7cm). A total of 10 Eels were captured during the survey, lengths ranged from 33cm to 44cm (mean length = 37.9cm). Fig.15 Lough Muck (Donegal) Frequency Length (mm) Fig.16 Length frequency Trout, Lough Muck 2012 (N=44) Page 18 of 21

19 Frequency Length (mm) Fig.17 Length frequency Eel, Lough Muck 2012 (N=10) 3.4 FISH AGE AND GROWTH Scales were taken from the trout caught during this survey for aging and back calculation of growth. Fig 18. Outlines the average length at age for the Brown trout caught during the survey. The length frequency distribution for Brown trout Fig 16. Highlights the presence of distinct age classes including young of the year or 0+ trout fry. Growth rates are slow but are comparable to other acidic oligotrophic loughs in Ireland. Feeding is limited which limits growth and age of the fish present. No eels were aged as part of this survey and were all released after measurement. Page 19 of 21

20 20 Lough Muck Co Donegal Length (cm) L1 Length at age L2 Fig 18. Trout growth back calculated growth rates for Brown trout caught in Lough Muck Co Donegal 2012 n = DISCUSSION Trout were the dominant species numerically in Lough Muck, Co Donegal. European eel were also present. Three age classes of trout were recorded from the survey. One large salmonid specimen was observed breaking the surface during the survey but no fish in this length class were caught. This is not that uncommon in smaller upland oligotrophic loughs were numbers are dominated by small fish. A number of larger piscivorous specimens may be present but in low numbers. No larger fish were caught in the floating nets which were placed over the deepest sections of the Lough. It is recommended that in any future survey that a number of braided nylon single panel floating gill nets are used in place of the monofilament floating gill nets used during this survey and that the mesh size is increased. 5.0 RECOMMENDATIONS Repeat survey every 5 years. Page 20 of 21

21 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. Deploy gangs of braided nylon single mesh floating nets over the deepest section of the lough to try and catch larger fish observed during the 2012 survey. Communicate findings internally to colleagues and externally to stakeholders Continue to conduct stillwater fish surveys temporally and spatially within the Foyle and Carlingford areas. Provide the fishery owner with a copy of the survey report. 6.0 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 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 21 of 21