Have Fisheries Caused Declines in American Eel Recruitment and Abundance?

This paper evaluates the hypothesis that fisheries reduce American eel populations through intergenerational effects, which occur when a fishery-induced reduction in species-wide spawner output leads to a decline in subsequent recruitment, and through intragenerational effects, which occur when fishing reduces the strength of a local population.  In eastern Canada, 93.6% of coastal eel habitat is unfished for eels, and in the US, much of the coastal eel habitat and nearly all freshwater habitat is unfished for eels.  On the basis of reported eel densities and habitat estimates, eastern North American saline waters contain 147,538,663 yellow eels, with a biomass of 42,771 t.  Mean reported landings for 2000-2010 were 1.5% of this biomass.  The high fraction of eel habitat that is unfished and the low estimated exploitation rate suggest that fisheries are unlikely to have substantial impacts on overall spawner output and subsequent recruitment.  If fishing reduces eel populations within generations, abundance trends should decline in areas that are heavily fished.  However, in five of 10 such cases, abundance trends increased or showed no trend.  These findings fail to support the notion that fishing causes eel declines, although they do not exclude the possibility that fisheries reduce populations in some areas.