European Smelt (Osmerus eperlanus L.) Baseline Surveys on the River Foyle, River Finn, River Deele & Burndennet River

Transcription

1 2010 European Smelt (Osmerus eperlanus L.) Baseline Surveys on the River Foyle, River Finn, River Deele & Burndennet River Loughs Agency of the Foyle Carlingford and Irish Lights Commission Report Ref: LA/Smelt/01, 04, 09 & 19/11

2 European Smelt (Osmerus eperlanus L.) Baseline Surveys on the River Foyle, River Finn, River Deele & Burndennet River 2011 For further information contact: Art Niven (Fisheries Research Officer) Loughs Agency 22, Victoria Road Londonderry Written and prepared by: Art Niven Maps Prepared by Rico Santiago BT47 2AB agency.org Page 2 of 18

3 Table of Contents Executive Summary... 4 Fig 1. Loughs Agency and Inland Fisheries Ireland staff conducting 2010 surveys Introduction Methods... 6 Fig 2. Fyke net recovery... 6 Table 1. Number and location of nets deployed in March 2010 Survey... 6 Table 2. Number and location of nets deployed in April 2010 survey... 7 Fig 3. Smelt sampling locations (2010) and known smelt distribution within the Foyle area Results... 8 Table 3. Smelt data sets presented in this report... 8 Fig 4. Approximate numbers of smelt recorded during impingement study. Note break in data in Aug 2008 when over 27,000 juvenile smelt were recovered during one sampling period Fig 5. Length weight relationship for Foyle smelt sampled during impingement study 2008/ Fig 6. Length frequency distribution for Foyle smelt sampled during impingement study 2008/09. 9 Table 4. Location of fyke nets and smelt caught th March Table 5. Location of fyke nets and smelt caught th April Fig 7. Length frequency by sex of smelt caught in March 2010 survey Fig 8. Length frequency by sex of smelt caught in April 2010 survey Table 6. Sex ratio and mean fork length and range of smelt caught in 2008/09 n = 1186, March 2010 n = 109 and April 2010 n = Table 7. By catch th March Table 8. By catch th April Note male perch were running with milt and ready to spawn Table 9. Combined catch from both smelt surveys in Discussion Fig 9. Picture on the left is a male smelt, note milt running from vent and picture on right is a female smelt, note eggs at vent Recommendations Conclusions Acknowledgements References Page 3 of 18

4 Executive Summary Biological data and temporal distribution for European smelt Osmerus eperlanus L. caught as part of an impingement study at a cooling water intake on the River Foyle in is presented. In addition data is presented for two targeted surveys for European Smelt which were conducted in 2010 as part of an ongoing partnership between Inland Fisheries Ireland and the Loughs Agency. The focus of the partnership is on researching fish species of national conservation and biodiversity importance within the Loughs Agency jurisdiction. Smelt have been recorded previously from a number of areas within the Foyle system including Coolkeeragh Power Station cooling water intake (Vickers and Watson 1974 & Vickers, 1974), the estuaries of the River Faughan and River Roe which discharge directly into Lough Foyle (P. Moorehead, Pers Com) and at a unnamed cooling water intake (McGonagle, Unpublished data). This report provides information on localised distribution within the upper River Foyle and its tributaries and at a cooling water intake and highlights a number of issues of concern relating to the long term conservation of the Foyle smelt populations. A number of recommendations for further study are made. The smelt populations of the Foyle are likely to be of national and international interest due to the size of the estuary and available freshwater spawning habitat. Fig 1. Loughs Agency and Inland Fisheries Ireland staff conducting 2010 surveys. Page 4 of 18

5 1.0 Introduction The European smelt is listed within the International Union for the Conservation of Nature and Natural Resources (IUCN) Red Data list and Irish Red Data Book. Listed as vulnerable within the Irish Red Data Book smelt have only been recorded in a small number of locations throughout the island of Ireland (Quigley et al, 2004). All Irish smelt are anadromous moving between estuarine/marine conditions and freshwater to reproduce (Doherty and McCarthy, 2004). Known spawning populations in Ireland are limited to the Foyle, Lower Shannon and Suir (Quigley et al, 2004). At a European scale smelt are found in estuaries from Norway to north western Spain and the Baltic Sea area, some purely freshwater non migratory populations exist. From a conservation and protection perspective accurate knowledge of the local spatial and temporal distribution, abundance and habitat utilisation is required in order to protect smelt populations from anthropogenic impacts and to ensure conservation through appropriate regulation. Data generated from this study will complement other data collected at an all Ireland scale and will contribute towards the knowledge base and future conservation of smelt populations in Ireland. Smelt are known to spawn from January to April in large clean rivers. Water temperature and moonlight have been highlighted as the main factors that affect timing of smelt spawning runs. Water temperature needs to be in the range of 4-9 C (Quigley et al, 2004). Prior to the surveys conducted in 2010 there were no known records of spawning smelt from the locations surveyed but due to the numbers of juveniles and maturing adults caught within the Foyle it was assumed that spawning may be taking place at the tidal limits of the River Foyle and within its tributaries. Data from the surveys outlined above are presented and local spatial and temporal distribution discussed in the context of existing knowledge of smelt biology and ecology. Page 5 of 18

6 2.0 Methods A long term high frequency fish impingement study was conducted by the Loughs Agency at a local cooling water intake between January 2008 and September A significant number of fish species were recorded highlighting the importance of both Lough Foyle and the River Foyle as a nursery ground for a great diversity of fish species including smelt. All fish were recorded individually except at certain times when a total weight per species was recorded. Targeted smelt surveys near and within the tidal limits of the upper River Foyle and its tributaries were conducted on two separate occasions in 2010, one between the 15 th and 16 th March 2010 and one between the 12 th and 13 th April Gangs of fyke nets were deployed at a slight angle to the flow in a variety of locations within the upper Foyle, lower River Finn, lower River Deele and lower Burndennet River. All locations were at or near the tidal limit. Fyke nets were deployed for one overnight period. Fig 2. Fyke net recovery Four gangs of fyke nets were deployed overnight during the period 15 th - 16 th March 2010 and five gangs of fyke nets were deployed overnight during the period of 12 th -13 th April The location of the nets is outlined in tables 1 and 2 and figure 3. Net Location Number of Nets Finn 1 Foyle 2 Deele 1 Total 4 Table 1. Number and location of nets deployed in March 2010 Survey Page 6 of 18

7 Net Location Number of Nets Finn 2 Foyle 2 Burndennet 1 Total 5 Table 2. Number and location of nets deployed in April 2010 survey Fig 3. Smelt sampling locations (2010) and known smelt distribution within the Foyle area. Page 7 of 18

8 3.0 Results Two separate data sets are presented in this section to outline the baseline data collected by the Loughs Agency and the Loughs Agency/Inland Fisheries Ireland. The survey results presented provide an overview of the data collected. Sampling Method of Period Capture 2008 & 2009 Impingement Study Location Lower River Foyle/Lough Foyle 2010 Fyke Nets Upper River Foyle and its tributaries Table 3. Smelt data sets presented in this report Sample Size 1186 (sub sample) 128 As part of a long term impingement study at a local cooling water intake a sample of all smelt impinged were taken on a weekly basis over a twenty one month period during 2008 and Figure 4 outlines the approximate number of smelt recorded during the impingement study as derived from actual counts or as extrapolated from average weight/total weight sampled. Number of Smelt Approximate Numbers of Smelt Recorded During Impingement Study /01/ /02/ /02/ /03/ /03/ /04/ /04/ /05/ /07/ /08/ /08/ /09/ /09/ /09/ /10/ /10/ /11/ /11/ /12/ /01/ /01/ /02/ /02/ /03/ /07/ /08/ /08/ /09/2009 Date Fig 4. Approximate numbers of smelt recorded during impingement study. Note break in data in Aug 2008 when over 27,000 juvenile smelt were recovered during one sampling period. Page 8 of 18

9 Length Weight Relationship of Foyle Smelt 2008 and 2009 n=1186 y = 2E 06x R² = Weight (g) Length (mm) Fig 5. Length weight relationship for Foyle smelt sampled during impingement study 2008/09 60 Length Frequency Distribution for Foyle Smelt 2008 & 2009 n= Frequency Length (mm) Fig 6. Length frequency distribution for Foyle smelt sampled during impingement study 2008/09 Page 9 of 18

10 Targeted smelt surveying was subsequently conducted in 2010 over two separate periods (March and April 2010) to ascertain spatial distribution at spawning time. Tables 4 and 5 outline the netting locations, netting effort and smelt caught per net. Net ID Location Number of Fyke Net Gangs Number of Smelt Caught Finn Fyke 1 River Finn 1 49 Deele Fyke 1 River Deele 1 9 Foyle Fyke 1 Upper Tidal Foyle 1 7 Foyle Fyke 2 Upper Tidal Foyle 1 56 Total Table 4. Location of fyke nets and smelt caught th March 2010 Net ID Location Number of Fyke Net Gangs Burndennet Fyke 1 Castlefinn Fyke 1 Burndennet River Number of Smelt Caught 1 0 River Finn 1 0 Finn Fyke 1 River Finn 1 0 Foyle Fyke 2 Upper Tidal 1 7 Foyle Foyle Fyke 1 Upper Tidal 1 0 Foyle Total 5 7 Table 5. Location of fyke nets and smelt caught th April 2010 Biological data in the form of length weight relationships and length frequency distribution differentiated by sex from both surveys in 2010 are highlighted in Figures 5,6,7 and 8. Page 10 of 18

11 Length Frequency of European Smelt Caught in the Foyle System, March 2010 n=109 Males Females Frequency < Length (mm) Fig 7. Length frequency by sex of smelt caught in March 2010 survey. 10 Length Frequency of European Smelt Caught in the Foyle System, April 2010 n=7 Males 8 Frequency < Length (mm) Fig 8. Length frequency by sex of smelt caught in April 2010 survey. Page 11 of 18

12 Smelt caught during the impingement study ranged in length from 4.1cm to 24.7cm and represented multiple cohorts. Sex ratios were not available for smelt caught during the impingement study. 85% of a sub sample of 109 smelt caught as part of the March 2010 study were male while 100 % of the April 2010 survey were male. Average fork length of smelt caught in the March 2010 survey was 17.7cm and ranged from 14.2cm to 22.1cm. Smelt caught in the April survey had an average fork length of 15.5cm and ranged from 13.4cm to 18cm (table 6). No scale reading for aging purposes was conducted for either study Survey Period % Male % Female Mean Fork Length (cm) Range (cm) 2008/09 Unknown Unknown N/A March April Table 6. Sex ratio and mean fork length and range of smelt caught in 2008/09 n = 1186, March 2010 n = 109 and April 2010 n = 7 Information on by catch recorded during the spawning surveys is outlined in tables 7-9. No by catch information is provided for the impingement study as this was a specific study concerning all fish species and was not limited solely to smelt. Species/Life Stage Number Salmon Kelt 1 Salmon Parr 3 Sea Trout 1 Trout Parr 5 Flounder 97 Total 107 Table 7. By catch th March 2010 Page 12 of 18

13 Species/Life Stage Number Flounder 184 Salmon Parr 3 Salmon Smolt 2 Trout Parr 3 Sea Trout Kelt 1 River Lamprey 3 Eel 16 Perch 12 Total 224 Table 8. By catch th April Note male perch were running with milt and ready to spawn. Total catch from both surveys are combined and presented in Table 9. Species/Life Stage Number Smelt 128 Salmon Kelt 1 Salmon Parr 5 Salmon Smolt 2 Sea Trout 1 Sea Trout Kelt 1 Trout Parr 8 River Lamprey 3 Eel 16 Perch 12 Flounder 281 Total 458 Table 9. Combined catch from both smelt surveys in Discussion The presence of large numbers of juvenile smelt observed as part of the impingement study highlighted the need for additional surveys within the Foyle to pinpoint spawning locations. This also dovetailed well with the research interests and expertise of Inland Fisheries Ireland Biologists Dr Jimmy King and Dr Sean Rooney who were eager to collaboratively survey the upper tidal limits of the River Foyle and its tributaries with the Loughs Agency. Page 13 of 18

14 The survey plan for the 2010 spawning season focused on delineating the spatial and temporal distribution of smelt at spawning time within the upper River Foyle and its tributaries area. This survey has provided the first detailed records at these locations of ripe smelt at spawning time with males observed running with milt and gravid females. Additional planned survey work to delineate actively utilised substratum and bankside features in future years should facilitate greater protection of these vulnerable spawning habitats. The study highlighted the importance of the tidal portions of our river systems not only as migratory highways for salmonids that are utilised on the way to and from the salmonid spawning and nursery grounds but also the diversity and importance of these areas as important spawning and nursery habitats in their own rights. Other native fish species actively and successfully utilise these habitats throughout the calendar year. Significant threats within these areas include in-channel aggregate (sand and gravel) extraction and dredging, water abstraction, extreme fly tipping, water pollution, poor and inappropriate bankside and riparian zone management, spawning substrate removal, inadequate legislative and regulatory protection and inadequate information on the status of smelt within the Foyle area and indeed across the island of Ireland. The 2010 survey results are not likely to be representative of the peak smelt run within the areas surveyed. Hutchinson and Mills (1987) reported that during the early stages of the spawning run on the River Cree in south eastern Scotland that sex ratios were quite even but as the run developed that males became more dominant. This was attributed to females dropping downstream after spawning while males remained to spawn with other females. It is highly likely that both the March and April 2010 surveys were conducted towards the end of the spawning run as evidenced by the dominant presence of males in the March sample and the absence of females from the April survey. There is considerable scope for expanding these surveys in future years to more accurately pinpoint local spawning runs by surveying slightly earlier than conducted during the surveys reported here. The first recorded presence of smelt in Ireland was from the Shannon, as Irelands largest estuary it is assumed that this is home to the biggest Page 14 of 18

15 populations of smelt. Over recent years significant survey work has been conducted to study and to document the biology and ecology of these populations. As part of this work water pollution and barriers to migration have been highlighted as major threats to smelt conservation in this area. One pollution event from an unknown source was responsible for killing over 10,000 smelt in the River Shannon in 2001 (Quigley et al, 2004). Similar events could impact upon the Foyle area smelt populations. As evidenced by the results of the surveys significant numbers and potentially different populations of smelt are present throughout the Foyle area. Large gaps remain in our knowledge and understanding of the localised ecology and distribution in both estuarine/marine and freshwater habitats. Additional work needs to be conducted to fill these gaps. Fig 9. Picture on the left is a male smelt, note milt running from vent and picture on right is a female smelt, note eggs at vent. 5.0 Recommendations European smelt are a unique piece of native fisheries biodiversity within the island of Ireland and are presently afforded little or no protection under national (NI & ROI) and European legislation. Smelt represent one of the most understudied components of Irelands native fishery biodiversity but may be one of the most threatened. Significant anthropogenic influences have the potential to severely threaten the existing populations. It is therefore imperative that continued research Page 15 of 18

16 into the ecology, distribution and abundance at both a national and local scales is conducted. The next stage in monitoring the distribution and ecology of the Foyle smelt populations should include a post spawning survey to identify sites where incubating eggs have attached to submerged substrate, vegetation and tree roots. This has been suggested by Dr Jimmy King and Dr Sean Rooney from Inland Fisheries Ireland and will hopefully be conducted in partnership with the Loughs Agency in spring This information would be invaluable in providing knowledge of actively utilised habitats and highlight the need for protection of these highly sensitive areas. As part of the cooling water intake fish impingement study genetic samples were provided to both Queens University Belfast and the University of Wales in Bangor. Further genetic analysis could be conducted to see if differentiation exists within the smelt population of a large river system like the Foyle. Continued monitoring should be conducted at all cooling water intakes to ensure effective screening is utilised and screening requirements are met. Novel fish screening solutions should be investigated as part of this process including sound and bubble curtains. Information should also be made freely available to the public to facilitate developing conservation partnerships and environmental education and outreach programmes and to raise awareness of the European smelt and potential threats to it within the Foyle area. Extended netting and habitat surveys should also be conducted to include the upper tidal sections of the rivers Mourne, Faughan and Roe concentrating on weekly surveys for a number of weeks pre and post 17 th March. This will assist with defining spawning run migration windows at all suitable sites. 6.0 Conclusions Knowledge of a population of smelt within the Foyle area is not new with observations and papers existing from the 1970 s. Little has happened Page 16 of 18

17 however in the intervening 40 years to conserve or protect this species. While it is proposed to create an offence under the Foyle Fisheries Acts to take or kill smelt without a licence in the Foyle and Carlingford areas this does not conserve or protect the actively utilised spawning habitats which are most at risk. The Foyle populations probably form a considerable proportion of the smelt population of the UK and Ireland and therefore should be afforded appropriate protection. The establishment of local Areas of Environmental Concern should be considered as part of any smelt conservation and monitoring strategy within the Foyle area. 7.0 Acknowledgements The Loughs Agency sponsoring departments and staff are gratefully acknowledged for their assistance in conducting smelt population monitoring in the Foyle area. Dr Jimmy King and Dr Sean Rooney from Inland Fisheries Ireland are also gratefully acknowledged for their guidance, conducting practical fieldwork and cooperation with all aspects of the 2010 surveys. 8.0 References Doherty, D., McCarthy, T.K The Ecology and Conservation of European Smelt (Osmerus eperlanus L.) from Waterford Estuary, In South Eastern Ireland. Biology and Environment: Proceedings of the Royal Irish Academy, Vol. 104B, No. 2, pp Hutchinson, P. and Mills D.H Characteristics of spawning-run smelt, Osmerus eperlanus (L). from a Scottish river, with recommendations for their conservation and management. Aquaculture and Fisheries Management 18, pp Quigley, D.T.G., Igoe, F. and O Connor, W The European Smelt Osmerus eperlanus L. in Ireland: General Biology, Ecology, Distribution and Status with Conservation Recommendations. Biology and Page 17 of 18

18 Environment: Proceedings of the Royal Irish Academy, Vol. 104B, No. 3, pp Vickers, K.U Occurrence of the Smelt Osmerus eperlanus (L.) in the Estuary of the Foyle. Irish Naturalists Journal, Vol. 18, No. 1, p. 24. Vickers, K.U. and Watson, P.S Observations on the fishes recovered from the intake screens of Coolkeeragh Power Station, River Foyle, in Foyle Fisheries Commission 22 nd Annual Report, App 3. Page 18 of 18