Serious Decline in Eel Stocks
Thursday, 26 July 2001
Release date: 17 July, 2001
In Ireland over 1,000 tonnes of eels, valued at £5 million, are captured annually. Most are exported to the continent, in particular to Holland and Germany, where eel is more of a delicacy than salmon and priced accordingly.
The eel is generally regarded as a typical member of the fish communities that inhabit Ireland s lakes and rivers. Frequently, scientific surveys have shown it to be among the more abundant species present in lowland river reaches and coastal streams. Indeed, in some isolated western Irish streams, like several on Clare Island, Co. Mayo, it may be the only fish species present.
Ease of natural recruitment to Ireland s inland waters by juvenile eels is thought to be a major factor in the success of the species here. Young eels that travelled thousands of miles across the Atlantic on the Gulf Stream current from spawning grounds in the Sargasso Sea, have in the past migrated into Ireland s rivers in spring and early summer each year in large numbers.
However, the situation is deteriorating and according to Dr Kieran McCarthy, of NUI Galway s Department of Zoology, a steady decline has been recorded in the quantities of elvers (young eels), entering Irish rivers. The River Shannon eel stock has experienced a steady decline in natural recruitment over the past three decades. The numbers of juvenile eels trapped at Ardnacrusha for stocking the Shannon lakes, has dropped from a peak of almost 7 tonnes in 1979, to an average of less than half a tonne in the past decade. Similarly, the numbers captured leaving the river as mature silver eels, migrating to their spawning area in the Sargasso Sea, has declined from an average of 28 tonnes per year in the 1980s and early 1990s to an average of 10 tonnes since the mid 1990s.
Although natural recruitment of juveniles to the river is the principal cause of the decline, other threats to the species include water quality problems and the spread of oriental eel parasites, accidentally introduced in recent years. The serious decline in juvenile eel numbers has also been observed elsewhere in Europe and the eel fisheries of countries from Scandinavia to the Mediterranean area are being seriously affected.
According to Dr McCarthy, "the available evidence suggests that the decline in juvenile eel populations arriving in European coastal zones is due to climatic effects on ocean currents. The Gulf stream, to which Ireland owes its mild climate, is also very important in marine ecology. Declines in eel, Atlantic salmon and other migratory fish, may be due to the changes in oceanic circulation patterns caused by global warming".
Having arrived safely in Ireland s rivers, eels often encounter many obstacles, which prevent them reaching lakes where most of the eel fishing takes place. Dr. McCarthy suggests that in order to facilitate their up-river journey, eel ladders should be installed at obstacles in rivers, which would help the eels on their way just as special fish passes in many Irish rivers, enable salmon to move upstream.
Irish eel researchers and fishery managers have played a pioneering role in the development of eel stock monitoring protocols and stock enhancement measures. At present, most of the eels caught in Ireland are from the intensively managed Lough Neagh fishery. It has been calculated that the productivity of our eel fisheries could be doubled or trebled, through scientifically managed stocking programmes. However, this will not be possible if the overall European stocks of eels are not conserved.
Sustainable exploitation of eel fisheries requires development of an international management plan. At a meeting in NUI, Galway last week, scientists from Sweden, Germany, Belgium, France, and Portugal discussed with eel researchers from Galway and Northern Ireland, the possible ways in which this goal might be reached. They called on national government agencies, including the Department of Marine and Natural Resources, to encourage the EU to provide on-going support for research on eels.
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