Research Document - 2013/132
Recovery Potential Assessment for the American Eel (Anguilla rostrata) in eastern Canada: functional description of habitat
By T.C. Pratt, R.G. Bradford, D.K. Cairns, M. Castonguay, G. Chaput, K.D. Clarke, and A. Mathers
Abstract
This document provides a review of the habitat requirements of the American Eel (Anguilla rostrata), with a focus on habitat needs by life stage, estimation of the amount of habitat currently available and currently inaccessible for eels, determination of whether habitat will be limiting if recovery objectives are reached, assessment of how different habitats influence eel biology and carrying capacity, and finally addresses whether American Eel habitat usage may meet the requirements of a residence as defined by the Species at Risk Act. The American Eel has a complex life cycle, spanning oceanic, nearshore coastal, estuarine and freshwater environments. Little is known about habitat requirements for migrating, spawning, egg and leptocephali (larval) stages in the ocean. After metamorphosis into glass eels, ingress into nearshore coastal, estuarine or freshwater is linked to diurnal and lunar cycles. During the inland migration and growth stage as elvers and yellow eels, respectively, water velocity and temperature, and substrate become more important habitat features. More than most fishes, American eels are influenced by their habitat because of the relationship between their highly variable life history characteristics and habitat features, including habitat-mediated impacts on growth and sex determination. The distribution of the American Eel covers a vast geographic area, and at current abundance levels, habitat is not thought to be limiting across most of its range. However, there are specific locations in northeastern North America where access to substantial quantities of habitat have been lost due to barriers; as much as 84% of freshwater habitat may be currently inaccessible. It is uncertain whether these habitat losses are sufficient to limit recovery. Overall, given the wide distribution of the species, localized areas of reduced habitat quantity and quality in either freshwater or marine areas are not likely to constrain the possibility of species recovery.
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