Population Decline of the American Eel: Implications for Research and Management

We present evidence for a decline in the population of the American eel (Anguilla rostrata) from several widely distributed regions of North America from 1984 to 1995. Trends in population indices from commercial catch data, upstream passage counts, and seine, trawl, and electrofishing surveys were analyzed and found to be either not significant or significantly negative. Explanations for this decline, whether natural or anthropogenic, are unknown, due to variation and incompleteness in abundance data, and incomplete knowledge of eel life history, ecology, and population dynamics. A number of potential factors may be contributing to the decline, including (in alphabetical order): barriers to migration, habitat loss and alteration, hydro turbine mortality, oceanic conditions, over-fishing, parasitism, and pollution. The paucity of life table data associated with the unconventional life history characteristics of anguillid eels (catadromy, panmixis, semelparity, high age at maturity, wide geographic distribution, and ecological generalist habit) prevents development of accurate population models and determination of overall effects influencing production and recruitment for this species. Historically there has been little attention to management of this species. A new coast-wide management initiative by the Atlantic States Marine Fisheries Commission has taken a conservative approach to limiting controllable and anthropogenic sources of mortality and enhancing recruitment and restoration of available habitat. Objectives of the plan include: improving knowledge of eel utilization through better reporting of harvest, increasing knowledge of eel population dynamics and life history, providing migratory passage and access to historic eel freshwater habitat, and monitoring of abundance levels of various eel life stages.