Lawton, C.

McCarthy, T.K.  Kieran

Nowak, D.

English

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University of Massachusetts AmherstScholarWorks@UMass AmherstInternational Conference on Engineering andEcohydrology for Fish PassageInternational Conference on Engineering andEcohydrology for Fish Passage 2016Jun 21st, 4:00 PM - 4:15 PMOcean Connections: Silver Eel (Anguilla anguilla)Production, Spawner Biomass Escapement andMitigation of Hydropower Eel Mortalities in theRiver Erne, IrelandT.K. "Kieran" McCarthyNational University of Ireland, GalwayD. NowakNational University of Ireland, GalwayC. LawtonNational University of Ireland, GalwayFollow this and additional works at: https://scholarworks.umass.edu/fishpassage_conferenceThis Event is brought to you for free and open access by the Fish Passage Community at UMass Amherst at ScholarWorks@UMass Amherst. It hasbeen accepted for inclusion in International Conference on Engineering and Ecohydrology for Fish Passage by an authorized administrator ofScholarWorks@UMass Amherst. For more information, please contact scholarworks@library.umass.edu.McCarthy, T.K. "Kieran"; Nowak, D.; and Lawton, C., "Ocean Connections: Silver Eel (Anguilla anguilla) Production, SpawnerBiomass Escapement and Mitigation of Hydropower Eel Mortalities in the River Erne, Ireland" (2016). International Conference onEngineering and Ecohydrology for Fish Passage. 47.https://scholarworks.umass.edu/fishpassage_conference/2016/June21/47SILVER EEL (Anguilla anguilla) PRODUCTION, SPAWNER BIOMASS ESCAPEMENT AND MITIGATION OF HYDROPOWER EEL MORTALITIES IN THE RIVER ERNE, IRELAND.T. K. “Kieran” MCCARTHY, D. NOWAK AND C. LAWTONNATIONAL UNIVERSITY OF IRELAND, GALWAY,Fish Passage 2016IRELAND’S EEL MANAGEMENT PLAN• EU EEL STOCK RECOVERY PLAN (2007) REQUIRES MEMBER STATES TO IMPLEMENT EEL MANAGEMENT PLANS (EMP) THAT RESTORE SPAWNER ESCAPEMENT TO 40% OF PRISTINE LEVELS.• IRELAND HAS NATIONAL AND RIVER BASIN DISTRICT EMPS SINCE 2009WHICH REQUIRE:• FACILITATION OF JUVENILE RECRUITMENT• CLOSURE OF EEL FISHERIES• MITIGATION OF HYDROPOWER• BIOSECURITY RESTRICTIONS ON ELVER STOCKING• PROTECTION OF EEL HABITATSUnimpactedShannonErneLeeLiffeyClady/CrollyEel habitat.ShannonLeeErneLower siteUpper siteUpper/Lower catchmentFerny GapLisnaskeaPortoraBelturbetKillashandraButlers Br.L. MacNeanExperimental fishing weir Roscor Br. UrneyL. GownaEstuaryRIVER ERNE SYSTEM• TRANS-BOUNDARY RIVER SYSTEM (Republic of Ireland and Northern Ireland)• CATCHMENT AREA: 4,375KM2• MEAN ANNUAL DISCHARGE: 94M3S-1• TWO HYDROPOWER STATIONS (HPS) IN LOWER RIVER ERNECathaleen’s Fall HPSHPSEnvironmental conditions and upstream  elver migration (trap catches)   April /May  2014 115kg mortality 22/4/201405010015020025005010015020025001/04/201402/04/201403/04/201404/04/201405/04/201406/04/201407/04/201408/04/201409/04/201410/04/201411/04/201412/04/201413/04/201414/04/201415/04/201416/04/201417/04/201418/04/201419/04/201420/04/201421/04/201422/04/201423/04/201424/04/201425/04/201426/04/201427/04/201428/04/201429/04/201430/04/201401/05/201402/05/201403/05/201404/05/201405/05/201406/05/201407/05/2014Catch [kg]Discharge [m3s-1]Trap 2 G5Trap 1 WEDischargeMortalityReview of Erne elver mortality by the Standing Scientific Committee on Eel (SSCE)SSCE CONCLUDED THAT 2014  ERNE ELVER LOSSES = 12,955Kg SILVER EELLimitations of this methodology for River Erne :• (1) Parameters derived for modelling eel populations in continental Europe;• (2) Mitigation involved immediate increase in spawner biomass escapement, though lost elverswould have taken c 19 years to reach silver female stage;• (3) Increased silver eel captures in winter prior to mortality event were not fully credited in calculations.Calculation of Silver Eel Equivalent (ICES Model)The ICES Silver Eel Equivalent (SEE) method works on the basis of the following:• 80% mortality occurs at settlement, typically between pigment stages VIAII and VIAIII.• An instantaneous lifetime mortality of 0.14 yr-1 (Dekker, 2000)• 50:50 sex ratio with males maturing at 11 years and 114g mean weight and females maturing at 19 years and 679.5g mean weightMITIGATION MEASURES FOR LOSS OF 115KG OF RIVER ERNE ELVERS • 8450KGS OF COMMERCIAL SILVER EEL CATCHES TO BE PURCHASED FOR IMMEDIATE RELEASE TO SEA.• TRAP AND TRANSPORT  ON THE ERNE CATCHMENT TO BE INCREASED BY 17,500KGS.• IN RECOGNITION OF THE QUANTITY (12,000KGS) ABOVE 3-YEAR ROLLING AVERAGE (50%) TARGET TRANSPORTED (POST EVENT)  IN 2014 6,500KGS OF THIS TO BE COUNTED AS PART OF ADDITIONAL QUANTITY• THE AGREED NET ADDITIONAL 11,000KGS TO BE ACHIEVED BY EXCEEDING THE ANNUAL TARGETS (SET BY SSCE) FOR T&T UNTIL SUCH TIME AS THE NET ADDITIONAL QUANTITY (11,000KGS) HAS BEEN EXCEEDED (WITHIN A MAXIMUM PERIOD OF 4 YEARS)• ESB, HAVING ALREADY UPGRADED EEL TRAPS TO BEST AVAILABLE, WILL KEEP OPERATIONAL MATTERS UNDER REVIEW IN THE LIGHT OF FUTURE DEVELOPMENTS IN TECHNOLOGY.ROSCOR BRIDGE FISHING SITE• Lowermost silver eel fishing site on the River Erne• Three coghill nets attached to the bridge pillars• Scientific monitoring site• Annual mark-recapture estimation of biomass silver eel eels migrating downstreamFERNY GAP FISHING SITESet 1Net 1Net 2Set 4N et 3Net 4Set 2Set 3199200201358359FlowFlowN0 500METERS [m]This map base on Lower Lough Erne map, Sheet 17 - 1:50 000. Made and published by ORDNANCE SURVEY OF NORTHERN IRELAND, BELFAST 19811km = 8cmSCALE     1 : 12 500Set 1Set 2Set 3Set 4Complex lake outlet fishing site (Lower Lough Erne): 4 sets of nets.CUMULATIVE CATCH PER ERNE SITE (2009 – 2015 SEASONS)Roscor Br.13.2%Ferny Gap36.8% Portora15.1%L. MacNean0.0%Lisnaskea7.2%Belturbet1.3%Urney12.6%Butlers Br.0.5%Killashandra8.5%L. Gowna4.8%Development of the River Erne T & T: Upper versus Lower catchment fishing site catches 9.415.921.326.2 24.332.236.90.013.547.715.115.917.802040602009/10 2010/11 2011/12 2012/13 2013/14 2014/15 2015/16TonesUpper Lower2015 / 2016 Season• PRODUCTION  = TOTAL T&T + BIOMASS MOVING DS OF ROSCOR BRIDGE (78,034KG)• T&T = 70.1% OF PRODUCTION • DAM MORTALITY CALCULATED USING PREVIOUS TELEMETRY DATA FOR VARIOUS FLOW REGIMES (CUMULATIVE DAILY ESTIMATES) = 6333kg (HIGH SPILLAGE/LOW GENERATION)• SPAWNER BIOMASS ESCAPEMENT = 91.8% of PRODUCTION • MITIGATION : EMP TARGET (50 % of P) plus extra 11,000 kg plus extra River Bann release, = SUCCESS and 4,689 surplusd/s C. Fall HPS16,944kgCathaleen’s Fall HPS20.11% mortalityAssaroe LakeRoscor Br.Fishing SiteFishing efficiencyOtherFishing Sitesu/s Roscor Br.27,136kgd/s Roscor Br.23,277kgCliff HPS8.88% mortalityT&T50,898kgT&T3,808kgSamples0kgSamples0kgMortality0kgSamples360kgMortality0kgESCAPEMENT71,650kg91.8% of productionPRODUCTION78,034kgMITIGATIONEMP Target:     39,017kgElver mortality: 11,000kgSurplus:             4,689kg8.0%Discharge<130m s3 -116.3%Discharge>130m s3 -1Dam mortality2,067kgDam mortality4,266kgM/R escape 302kg≈T&T54,706kg70.1% ofproductionRelease of commercial silver eel catches (8540kg) on the River Bann in Northern Ireland• Two silver eel fishing weirs are still fished commercially on the River Bann • Lough Neagh Eel Fishermen’s Cooperative provided 8540kg  for release to the estuary• These silver eels would otherwise be sold for human consumption in the NetherlandsRiver Erne  T & T Catches (versus a 50% of Silver Eel Production Target)020,00040,00060,00080,0002012/13 2013/14 2014/15 2015/16KgCatch Production / TargetIreland, 60%GermanyFranceSwedenNetherlandsLuxembourgNew ZealandNorth AmericaN. B.Poor eel quality in Europe limits potential contribution to spawner populationPost EMP T&T (254t)67% of European total66% FemalesHPS Mortality ReductionT&T (254t) saved c. 53tOver 190 billion (190x109) eggs*Silver Eel T&TSummary Statistics (to 2014) * R. MacNamara and T.K. McCarthy 2012. Size-related variation in fecundity of European eel (Anguilla anguilla).ICES  Journal of Marine Science, 69: 1333-1337.Overview and Conclusions1. Elver mortalities can be  expensive !2. 115kg River Erne elver mortality : Release of silver eels (8450Kg)from a commercial fishery; increased trap and transport of silver eels (17,500Kg) past the dams; new elver traps and new monitoring systems.3. Mitigation was successfully completed in one year (Target <4 years).4. The successful mitigation involved: high costs, unusually favourable weather and increased fishing effort/ efficiency.5. Biosecurity concerns prevented restoration using imported elvers (>5%  of cost).Thank You For Your Attention 

Ocean Connections: Silver Eel (Anguilla anguilla) Production, Spawner Biomass Escapement and Mitigation of Hydropower Eel Mortalities in the River Erne, Ireland

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Ocean Connections: Silver Eel (Anguilla anguilla) Production, Spawner Biomass Escapement and Mitigation of Hydropower Eel Mortalities in the River Erne, Ireland

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