Science Advisory Report 2013/078

Recovery potential assessment of American Eel (Anguilla rostrata) in eastern Canada

Summary

• The American Eel (Anguilla rostrata) is a panmictic species with spawning occurring in the Sargasso Sea as a mixed pool of spawners originating from all eel producing areas across the species range.
• Trends in indices support the conclusion from COSEWIC that there has been a decline in American Eel abundance over the past 32 years with declines having been most severe in the St. Lawrence Basin and specifically Lake Ontario. Some indicators show recent (16-year) upturns in abundance, which have yet to manifest themselves as improvements in standing stock indices.
• Eels utilize a diverse range of habitats including fluvial and lacustrine fresh water habitat, brackish waters, and full saline water habitats. Habitat access to freshwater in both the United States and Canada has been reduced, most significantly in association with the construction of large dams having no or inadequate fish passage facilities for American Eel.
• At current abundance levels, it is unlikely that habitat availability presently limits production of eels over broad spatial scales. Over the long term, as the eel population grows and recovers, restoring access to habitats will likely be necessary to achieve long-term abundance objectives.
• Recovery targets for distribution and abundance are defined for short term (about one generation, 16 years), medium term (about three generations, 50 years), and the long term time frames.
• The short term distribution objective is to ensure no further loss of accessible habitat and to provide safe fish passage to and from areas rendered inaccessible over the past 16 years. Overall for eastern Canada, the short term objective for distribution may have been achieved but the medium-term objective to increase fish passage access to and from productive areas equivalent to what has been lost over the past three generations has not been realized.
• The short term abundance target of arresting decline and showing increases in the indices has been achieved for the recruitment life stage but the increased recruitment has yet to manifest itself in improvements in the standing stock indices. The medium term recovery targets for abundance are the mean values of the indices for the period 1981 to 1989. Overall for Canada, the medium term recovery targets for all life stages have not been attained.
• The threats assessed at medium or high level of concern which are common to most jurisdictions in eastern Canada include commercial fisheries on large eels and those associated with physical obstructions (loss of habitat and fragmentation of habitat).
• Mitigation options and alternatives to current activities considered to be threats to American Eel are available.
• The maximum allowable harm that the species can sustain and not jeopardize survival or recovery of the species could not be adequately quantified due to limitations in population modeling associated with lack of quantitative data on abundance and life history characteristics, and uncertainties of the population dynamics for this species.
• Processes that determine the recruitment to the continental waters of the early life stages which hatch, grow and disperse from the spawning grounds in the Sargasso Sea remain unknown.
• The greatest uncertainties in the recovery potential assessment relate to how regionally specific indices and trends of recruitment, standing stock, and silver eel production depend upon the total spawner abundance over the species range compared to the spawner production originating from each region.
• Wintering burrows used by eels in some areas of eastern Canada may meet the definition of residence under the Act.
• The assessment of the status of the American Eel would benefit from coordinated monitoring and assessment efforts across the species range. This would require coordination with US and Caribbean countries.

This Science Advisory Report is from the June 11 to 14, 2013 Recovery Potential Assessment of American Eel (Anguilla rostrata) from Eastern Canada. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Complete document (PDF, 2,038 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.