Concurrent Sessions D: Fish Passage Around the World - I - Juvenile Eel Recruitment in the River Shannon, Ireland: Impact of Hydropower, Development of Mitigation Measures and Decline in Eel Numbers
Location
Agriculture Science Theater, Oregon State University
Start Date
25-6-2013 1:50 PM
End Date
25-6-2013 2:10 PM
Description
The River Shannon has been regulated for hydroelectricity generation since construction of the Ardnacrusha dam and associated structures began in 1929. Adverse effects on eel fisheries became evident within about two decades and, following compensation payments to fishery stakeholders, the Electricity Supply Board assumed a statutory fishery management role. Stock restoration measures were focused on capture of juvenile eels in the lower section of the river system and in estuarine tributaries. The trapping protocols that were developed and the results of studies on natural upstream migration of eels will be described. Diel, lunar and seasonal migratory cycles by glass eel, elvers and fingerlings (bootlace eels) were investigated using a variety of techniques that included: monitoring trap catches, use of experimental fishing methods, video observations and mark-recapture experiments. The effects of environmental factors, including water temperature, discharge, light and lunar cycles, in upstream juvenile migration were demonstrated. Modelling of long-term trends in recruitment, eel fishery yield and spawner escapement, suggests that the eel populations of the river system will undergo a serious decline within a decade. Facilitation of upstream migration of juvenile eels is therefore being prioritised in current research and management programmes.
Concurrent Sessions D: Fish Passage Around the World - I - Juvenile Eel Recruitment in the River Shannon, Ireland: Impact of Hydropower, Development of Mitigation Measures and Decline in Eel Numbers
Agriculture Science Theater, Oregon State University
The River Shannon has been regulated for hydroelectricity generation since construction of the Ardnacrusha dam and associated structures began in 1929. Adverse effects on eel fisheries became evident within about two decades and, following compensation payments to fishery stakeholders, the Electricity Supply Board assumed a statutory fishery management role. Stock restoration measures were focused on capture of juvenile eels in the lower section of the river system and in estuarine tributaries. The trapping protocols that were developed and the results of studies on natural upstream migration of eels will be described. Diel, lunar and seasonal migratory cycles by glass eel, elvers and fingerlings (bootlace eels) were investigated using a variety of techniques that included: monitoring trap catches, use of experimental fishing methods, video observations and mark-recapture experiments. The effects of environmental factors, including water temperature, discharge, light and lunar cycles, in upstream juvenile migration were demonstrated. Modelling of long-term trends in recruitment, eel fishery yield and spawner escapement, suggests that the eel populations of the river system will undergo a serious decline within a decade. Facilitation of upstream migration of juvenile eels is therefore being prioritised in current research and management programmes.
Comments
Dr T. Kieran McCarthy, though recently retired from active teaching, is actively involved in researching various aspects of European eel biology. His research on Irish eel populations , which involves studies on both upstream and downstream eels, is now mostly focused on hydropower regulated rivers. He works with various national and international resesarch partners. Since 1992 he has been collaborating with Electricity Ireland (formerly the Electricity Supply Board) in management of eel populations on the River Shannon.