European Eel Research

The European eel Anguilla anguilla is a fish of significant ecological importance. It is one of only 15 native fishes present in Ireland’s freshwater ecosystems and is perhaps the most recognisable of all our fauna. In recent decades, this species has undergone a dramatic decline throughout its range. The European Eel is a unique indicator of the environmental health and integrity of our oceans, estuaries and freshwaters, and its recent decline is seen as a serious environmental matter.

In response to the decline in European eel populations European Council Regulation 1100/2007 “Establishing measures for the recovery of the stock of European eel” has now been adopted in member states.

With funding from the ESB and in co-operation with the National University of Ireland, Galway, a major study on European eel in the Shannon estuary and Lower Shannon and Shannon estuary was undertaken by Dr. William O’Connor of ECOFACT during the period 1995-2003. This is largest juvenile eel research project to ever be undertaken in Ireland. This major research project included the following detailed studies:-

• Immigration timing and activity rhythms of glass eel in the Shannon estuary in relation to temporal and environmental factors
• Factors influencing the upstream riverine migration of juvenile European eel on the River Shannon and selected tributaries of its estuary
• Size structure and development stages of migrant European eel populations, and the size selectivity of various trapping methods
• Fish census results at the Ardnacrusha Borland fish-lift, with particular reference to European eel
• Interactions of juvenile European eel, brown trout Salmo trutta and other predators, in the tidal section of the lower Shannon River
• The assessment of European eel densities and population structures in the lower reaches of rivers in the Shannon estuary area using electrical fishing
• Bycatch fish species recorded during the operation of a pilot scale glass eel fishery on the Shannon estuary

During the study exceptional results were obtained in relation to catching glass eels and elvers. Indeed, over 20 million juvenile eels captured and transported upstream on the River Shannon, to above the Shannon hydroelectric scheme . The key finding of the study was that despite the global downturn in eel numbers hugely significant catches of both glass eels and elvers could be made with determined and focused effort. Indeed, the annual catches made during the study period (1997-1999) exceeded the catches of any the previous catches since 1980, and (temporarily) reversed the decline in eel catches recorded on the River Shannon.

The results of this study call into question the validity of many juvenile eel index sites in Ireland as it is clear that catch effort, and the quality of this effort, can have a highly significant influence on results obtained. It is also clear that an urgent best effort approach is needed now to maximise use of available glass eel and elver resources to save this species and restore its fisheries. Banning of all eel fishing, which is has occurred in Ireland, may not be the most prudent use of available glass eel and elver resources.

To access the report just click on this link: ‘Biology and Management of European Eel (Anguilla anguilla, L) in the Shannon Estuary, Ireland‘.