Science Advisory Report 2010/062

Status of American Eel and progress on achieving management goals

Summary

• The American Eel (Anguilla rostrata) is a panmictic facultatively catadromous species, spawning in the Sargasso Sea. Juvenile and adult stages historically occurred in all accessible freshwater, estuarine and coastal areas connected to the Atlantic Ocean, as far north as the mid-Labrador coast and as far inland as Niagara Falls above Lake Ontario.
• The long-term goal expressed in the draft management plan is to rebuild overall abundance of American Eel in Canada to its level in the mid-1980s with the short term goal to reduce eel mortality from all sources by 50% relative to the 1997 to 2002 average.
• Region-specific status indices show that abundance relative to the 1980s is very low for Lake Ontario and upper St. Lawrence River stock, and either unchanged or increasing in the Atlantic Provinces.
• In Ontario and Quebec, the closure of fisheries and buyback of licences has resulted in reductions in total mortality of eels from fishing (measured as landings) of greater than 50% relative to mortality during 1997 to 2002.
• Declines in fisheries landings (by weight) of 27% were noted for the DFO Maritimes Region whereas average landings in DFO Gulf Region and in Newfoundland have increased or remained unchanged. Decreased landings in the Maritimes may be confounded by issues of underreporting. Increased landings in the southern Gulf of St. Lawrence despite tightening of management rules are attributed to increased abundance of eels in this region.
• There has not been any demonstrated progress in reducing mortality of eels during passage through turbines in medium and large hydroelectric generating stations.
• Changes in landings are an insufficient measure of the effectiveness of management measures in reducing mortality. With the objective to increase escapement in the long term, a reduction in mortality rate, expressed as a proportion of the population that is killed, is the appropriate measure of performance.
• Mortality rate reference points must be developed to assess in the long term the sustainable level of mortality, and in the short term the levels of mortality which will not preclude the rebuilding objective of American Eel abundance over its range.
• The region-specific abundance levels of the mid-1980s are considered reasonable objectives for the American Eel. This period corresponds to a mid-level of abundance, expressed either as landings in fisheries or as indicated by fisheries-independent indices.
• Loss of habitat associated with restricted fish passage, contaminants, ecosystem changes in Canadian waters and broad-scale oceanographic variation all contribute to the cumulative stress on American Eel in eastern Canada. The consequences of all of these to eel survival, reproduction, recruitment and rebuilding are poorly known.

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