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Eel Monitoring Programme
In response to advice from the International Council for the Exploration of the Sea (ICES) that the European eel (Anguilla anguilla L.) is endangered and that the fishery is unsustainable the EC regulation establishing measures for the recovery of the European eel (Council Regulation 11000/2007) was created.
- Latest Advice...
- Scientific Eel Fishery
- 2012-2014 Executive Summary
- Eel Working Group
- Selected Publications
- European Eel Migration Study
The latest advice from International Council for the Exploration of the Sea (ICES) recommends that anthropogenic mortality on eel production and escapement should be reduced to, or kept as close to, zero as possible.
You can find more information on ICES’s advice on eels in 2016 here:
Summary from the Working Group on Eel (WGEEL)
Summary of the Working Group which consists of representatives/ members of the International Council for the Exploration of the Sea (ICES), European Inland Fisheries & Aquaculture Advisory Commission (EIFAAC) and General Fisheries Commission of the Mediterranean (GFCM):
In 2016, the Working Group on Eel (WGEEL) glass eel recruitment indices remain low at 2.7% of the 1960–1979 reference level in the ‘North Sea’ series, and 10.7% in the ‘Elsewhere’ series. The ‘recruiting yellow eel’ index was 21% of the level during the reference period.
The Eel Management Plan silver eel biomass and mortality rate estimates (reported in 2015) indicate the stock in the EU-assessed area is not within the biomass limits of the Eel Regulation and in most management units, anthropogenic mortality exceeds a level that can be expected to lead to recovery.
WGEEL attempts to cross-check glass eel catch with records of their fate (consumption, restocking and aquaculture) reveal major discrepancies between reporting systems. About 32% of the catch for 2015 has no recorded fate (about 36% for 2016). The lack of transparency in glass eel markets and movements is a cause for concern; far too high a proportion of the catch goes to ‘unaccounted for’ destinations and as such has to be considered as a total loss to the stock. Read the report of the Working Group on Eels here:
Scientific Eel Fishery -
Inland fisheries Ireland is in the process of setting up a network of scientific fisheries for eel around Ireland. These scientific fisheries will cover the different life stages (elver, yellow and silver eel) and be distributed in key catchments around Ireland. The purpose of the fisheries is to increase the data and knowledge of eel in Ireland ahead of the next EU review in 2018 which will help inform management on the state of the eel stocks.
For more infomation on how to get involved and applications see: Scientific Eel Fishery Application Information
Inland Fisheries Ireland was tasked by the Department of Communications, Energy and Natural Resources to set up a scientific eel fishery to further develop knowledge of the eel species and its prospects for recovery in Ireland.
When deciding on how best to use the limited resources available the following criteria were taken into account. The eel is a long lived migratory species with a complicated life cycle. To get a clear picture of the state of the eel stock it is necessary to monitor the different life stages of the eel; glass eel/elver, yellow eel and silver eel. In addition to ensuring the different life stages were monitored a spread of long term and short term data needs were assessed.
A recovery in the eel stocks will first be visible in the recruitment of glass eels and elvers back to our inland waters. A new glass eel or elver monitoring station will take 3-4 years before it will be used by IFI or by the ICES Eel working group as these assessments require a trend to be visible in the data and therefore a number of years of data is required. The elver stations are a long term programme and if operated efficiently they will provide important information on the spread of eel recruitment around Ireland. By setting up the elver stations within an Eel Index Catchment the data will also be used to understand the dynamics affecting the structure and distribution of eels within a catchment.
The yellow eel data from the lake and estuary scientific surveys (catch per unit of effort, length distribution, age and growth) can be used straight away to populate the different eel models available and will meet the short term data needs. The surveys are of short duration 10 to 25 days allowing more locations to be assessed. The data gathered will be available for review of the eel stocks by IFI on an annual basis. Information on yellow eels can be used to estimate silver eel escapement in areas where it is not feasible to set up a silver eel fishery.
Determining silver eel escapement using a direct silver eel fishery is the ideal scenario however due to the cost associated with setting up a fishery and the resources required to determine the escapement efficiency, IFI were limited to 2 new locations. The silver eel fishery is a long-term programme and will require a number of years to get an accurate escapement estimates using mark recapture techniques. A number of years will also be needed to observe the trend in the catch and get a picture of the stock structure using length distribution, age and sex ratios.
Taking this information into account it was proposed to target the 3 types of fisheries (glass eel/elver, yellow and silver). The yellow fisheries will provide information to be used straight away, the glass eel/elver and silver eel data will be an investment in the future which requires a commitment from funding sources and personnel involved.
The limited work proposed in the Shannon, Erne and Lee catchments were due to the existing IFI and ESB programmes already operating in these catchments. As a result of the knowledge already present in these systems IFI decided to invest in scientific surveys in the areas where more detailed scientific knowledge is required for example Eastern River Basin District (RBD), South East RBD, South West RBD and the Western RBD. By focusing resources in these areas there will be more data available to IFI when reporting to the EU on the recovery of eel in Ireland.
If you have any questions in relation to the Scientific Eel Fisheries you can write to:
‘Scientific Eel Fishery ’
Inland Fisheries Ireland,
3044 Lake Drive,
Citywest Business Campus,
2012-2014 Executive Summary
In response to advice from ICES that the European eel was critically endangered the EU Council Regulation 11000/2007 for the recovery of the eel stock was created. Under this regulation Ireland compiled a National Eel Management Plan to conserve eel stocks in Ireland, within this plan was a list of monitoring objectives. The aim of the IFI eel monitoring programme is to improve our understanding of the state of the eel stock in Ireland and fulfil the objectives as outlined in the national management plan. As part of the regulation a review of the management plan is due every 3 years. Ireland submitted the first review in June 2012 covering the years 2009 – 2011. This report is an account of monitoring actions taken in the years 2012 – 2014.
Over the course of the 3 years an increase in recruitment has been observed in some locations around Ireland and in Europe as a whole. The latest advice from ICES indicates an increase from 5% in 2011 to 12% of historic levels in 2014. However it remains to be seen if this increase in recruitment is as a result of the management measures put in place since 2009 or is just natural variability in the recruitment indices. IFI plan to continue to monitor the index sites around the country over the coming years.
IFI have successfully reached all monitoring objectives as outlined in the National Management Plan for the reporting season 2012-2014. The EMP programme has strived to monitor the different life stages of the eel where possible (elver, yellow eel and silver eel). In order to determine the level of recruitment of eels within key locations a long term elver monitoring programme was enhanced. Six locations around Ireland are monitored from April to August using a ramp style trap. The traps catch a proportion of the elvers actively migrating into freshwater. The traps are fished consistently on an annual basis in order to record the general trend in recruitment. This data series recorded the general decline in recruitment over the last decade and it is anticipated that the extended data series will record any changes to the trend as a result of the management measures implemented in Europe.
To fulfill objective 2; estimate silver eel escapement, a research silver eel fishery was operated in the Fane catchment on the east coast of Ireland from 2012 to 2014. A mark recapture study has been used to determine the efficiency of the fishing site and to determine the level of escapement of silver eels from the catchment. Due to the presence of three silver eel locations on the west coast (Shannon, Erne and Burrishoole) a second east coast research silver eel fishery was set up in the Barrow catchment in 2014 on a pilot basis. The Barrow is a large riverine dominated catchment in contrast with the other silver eel locations which all have large lake habitat. This location will enable us to investigate if there is a difference in the production and stock structure of silver eels escaping from river dominated habitat compared with lake dominated habitat.
To fulfil the remaining monitoring objectives; surveys of the yellow eel population in key locations were carried out using different survey methodologies. An intensive fyke net survey was carried out in 5 lakes (Lough Key, Ramor, Oughter; Lough Derg and Lough Muckno). A semi quantitative eel specific catchment wide electrofishing survey was carried out in the Fane catchment and in the Kells Blackwater, a subcatchment of the Boyne River. This electrofishing study was to investigate the distribution of eels in the rivers surrounding 2 large lakes (Lough Muckno and Ramor). A fyke net survey was carried out in the freshwater and transitional waters of the River Barrow to compare with historical information available. The brackish lagoon in the South Sloblands was resurveyed due to the presence of historical information available from the Fisheries Research Centre.
To determine parasite prevalence and eel quality a number of eel samples are taken back to the laboratory for further analysis. Parasite prevalence by Anguillicola crassus ranges from 48% to 83% in lakes and 68% in the freshwater river section of the River Barrow. An investigation into the extent of the distribution of A. crassus in Ireland was undertaken using data from the Eel Monitoring Programme and Water Framework Directive (Becerra Jurado et al. 2014). The prevalence and intensity of infections across 234 sites and 93 river basins in Ireland comprising rivers, lakes and transitional waters were analysed. While only 32% of the river basins were affected by this nematode, they correspond to 74% of the total wetted area of Ireland. As a result of this work the group have focussed on monitoring the damage the infection causes to the swimbladder of eels using 2 methods, The Swimbladder Degenerative Index (SDI; Lefebrve et al. 2002) and the Length Ratio Index (LRI; Palstra et al. 2007). Initial results from Lough Key and Lough Muckno indicate that the swimbladders of the yellow eels examined have slight to moderate damage. This is encouraging as there are reports in Europe with eels recording severe damage to the swimbladders (Lefebrve et al. 2002) however this is preliminary data and needs to be continued in a number locations to get a clear picture of swimbladder health.
The average growth rate of yellow eels examined is 2.75 cm/yr. The yellow eels range in age from 4 – 45 years for female and from 4 – 23 years for males. The average growth rate for silver eels is 2.52 cm/yr. The age of silver eel sampled ranges from 8-50 years for female from 6-27 years for males.
Electrofishing data from 2 catchments have highlighted the importance of habitat in the distribution of eels within catchments. The absence and low density of eels within the rivers and streams around Lough Muckno and Lough Ramor have drawn attention to the danger in assuming eels are widespread and inhabit all waterbodies. This will have knock on effects on attempts to model eel production and escapement from non-surveyed catchments. The importance of habitat and quantifying habitat needs to be addressed in the future.
Preliminary evidence suggests that there could be a change in the stock structure of eels in our lakes and transitional waters. The absence of small eels in the fyke net catches in our lakes and the increase in small eels in the transitional waters compared with historical data suggests a potential reduction in the distribution of eels within our catchments with smaller eels remaining in the transitional waters for longer due to the improved conditions resulting from the decreased density of eels. This data is preliminary and needs to be further investigated.
The IFI monitoring programme has caught 5,042 yellow eels and measured 4,851 silver eels over the three years. Parasite prevalence and intensity and sex differentiation were recorded for 841 eels. From the 6 years of data available (2009 – 2014) 2,057 eels have been aged and growth rates calculated. All of this information will be used to improve our knowledge of the state of the eel stock in Ireland and will be used to update the modelling of eel production and silver eel escapement from Ireland in compliance with the EU Eel Regulation (1100/2007).
As a result of the 6 years of monitoring it is proposed to concentrate work on Eel index catchments in order to determine the extent of eel distribution within catchments as a whole (transitional waters, rivers, lakes and tributaries). This will ensure an even spread of monitoring activities within each River Basin District for all life stages recorded and in all water body types. It is hoped that the data gathered under a long term index catchment monitoring programme will aid in the modelling of eel distribution, production and escapement in the future.
Eel Working Group
In 1976 a joint symposium between EIFAC and ICES was held in Helsinki to discuss Eel Research. As a result of that meeting a joint EIFAC/ICES working group on Eel was established in 1977 and they have been meeting annually ever since. The main aim of the Joint EIFAAC/ICES Working Group on Eels (WGEEL) is to report on the status of the European and American eel stocks and provide advice to support the development and implementation of EC Regulation No. 1100/2007 for eel stock recovery. The working group publish a report on their activities every year with detailed stock assessments and discussions on the state of the stock. The report also contains advice on standardising monitoring programmes across member states to ensure the best available data is evaluated, these programmes include monitoring eel catches at different life stages as well as the quality of eels in European waters. In November 2014 the working group held its first meeting with participation from General Fisheries Commission for the Mediterranean (GFCM) in Rome and is now the Joint EIFAAC/ICES/GFCM working group.
Joint EIFAAC/ICES/GFCM Working Group home page
The latest advice from ICES
‘The status of eel remains critical and ICES advises that all anthropogenic mortality (e.g. recreational and commercial fishing, hydropower, pumping stations, and pollution) affecting production and escapement of silver eels should be reduced to – or kept as close to – zero as possible.’
The latest advice from ICES is available here:
Eel Monitoring Programme reports
Inland Fisheries Ireland has contributed to research which will help solve one of the deepest secrets of oceanic migration and behaviour to one of Europe’s most mysterious fish, the European Eel.
Empirical observations of the spawning migration of European eels: The long and dangerous road to the Sargasso Sea. Behavioural Ecology.
Using data from silver eels released during autumn from the coasts of Sweden, France, Germany and Ireland, we have mapped the main migration routes from Europe to the Azores region, approximately half the distance to the eel spawning area in the Sargasso Sea. The project uncovered details of the migration that were previously hypothesized or simply unknown. The eels undertook a range of migration speeds ranging from 3 – 47km day -1 and underwent vertical migrations through the water column increasing the distance the eels were required to swim.
The telemetry data suggests that while some eels will undertake a fast migration and arrive for next spawning season it takes the majority of eels longer to migrate to the Sargasso Sea than we originally thought. It is hypothesised that the majority of eels arrive in time for spawning the following year, thus extending an already long lifespan by another year.
The study showed the high risk of predation on eels migrating from our European coastal waters. The eels from Ireland and the Mediterranean showed the highest predation rates where 27 of the 44 eels tagged and released from Galway succumbed to a predation event. The suspected perpetrators ranged from marine mammals, pelagic fish and sharks to deep sea fish; this hypothesis is based on the different temperature and depths recorded by the satellite tags after ingestion.
From 2006 to 2012, a total of 237 silver eels from the Shannon, Corrib, Erne and Burrishoole catchments were tagged. Of these eels, 98 eels were tagged with a satellite tag, the rest with internal or external data storage tags. Despite the high predation risk and a slight detour, one Irish eel tagged in Galway on the 4th November 2008 did make it to the Azores a travelling a distance of 6,982 kilometres and 273 days at sea.
To read the full research article published in Science Advances, visit http://advances.sciencemag.org/content/2/10/e150169 .
The research was led by the Centre for Environment, Fisheries and Aquaculture Science (Cefas) in collaboration with researchers from Inland Fisheries Ireland, University of Agricultural Sciences (Sweden), the Technical University of Denmark (Denmark), the French Natural History Museum (France), the University of Perpignan (France), the Norweigan Institute for Nature Research (Norway), the National Museum of Natural Science (Spain), the Institute of Inland Fisheries (Germany) and the University of Porto (Portugal).