The European eel is classified as critically endangered in the International Union for Conservation of Nature (IUCN) Red List of threatened species. European eels spawn in the Sargasso Sea, and after hatching as larval eels, they drift on the Gulf Stream ocean current until they reach the Atlantic coasts of Europe and transform into glass eels. Sadly, the number of young eels reaching our waters has declined over the past 30 years and amounts to as little as 8% of what was present during the 1970s.
Working to recover stocks
The Eel Monitoring Programme began in 2009 to monitor the population of European eel in Ireland’s rivers, lakes and estuaries. This programme was created in response to European legislation that required member states to develop an eel management plan and to establish measures for eel stock recovery.
The cause of their decline
While measures to promote eel stock recovery included the suspension of commercial eel fishing, overfishing was not the only reason for their decline. Other factors include water pollution, habitat loss, climate change, barriers to migration, parasites and diseases. The Eel Monitoring Programme monitors eel stocks and examines the potential causes for their decline.
Focusing our efforts
To do this, we focus on key index catchments, which include the Fane, Barrow, Munster Blackwater, Corrib, Shannon and Erne river systems. We study all stages of their life cycle and use a variety of netting methods, including fyke nets, coghill nets, baited pots, fixed traps and electric-fishing. Tagging studies helps us to estimate population size, while acoustic telemetry allows us to track eel movements.
In the laboratory, we gather information on diet, gender, age and growth rate. Of particular interest to us is the swim bladder, a gas-filled organ that many fish species use to regulate buoyancy while swimming. This organ can become infected by an invasive parasitic nematode worm called Anguillicola crassus, which causes damage and thereby potentially affects swimming performance and migration. For more information on eel migration, please visit our webpage for the EELIAD Project below.
A long term goal
Eels live for a long time, with reports of them reaching as much as 100 years of age. Eels of up to 50 years of age have been recorded by the Eel Monitoring Programme. On average, female eels leaving Irish waters to spawn are older than 20 years of age.
Unfortunately, the longevity and complicated life-cycle of eels make attempts to conserve them even more difficult. Any positive impact from our work could take a long time to show benefits: eel conservation is a long-term mission.
Click on the gallery above to view images from the Eel Monitoring Programme.