Life History of American Eels from Western Newfoundland

—Biological data are limited for American eels Anguilla rostrata from the northern portion of the species’ geographic range. The biological characteristics of American eels from two sites in western Newfoundland varied by sex, maturation stage, and habitat. Female and male sexually mature (silver) eels from the Castors River were comparable in length range with eels reported from other Newfoundland sites. Female silver eels from the Castors River began their spawning migration at a lower developmental stage for the gonadosomatic index, eye index, and pectoral fin length index than did eels from more southerly sites in eastern Canada and the United States. Annual growth rate declined with increasing age (r 1⁄4 0.93, P , 0.001). The growth rate at a given age was higher for eels from Muddy Hole (an estuarine habitat at the mouth of Flat Bay Brook) than for those from the Castors River (a freshwater habitat) primarily because growth rate decreased with an increasing proportion of residence in freshwater (r 1⁄4 0.74, P , 0.001). Most eels (64– 72%) from both sites had a history of occasional migration between and residence of variable duration in both freshwater and saline water, as determined from otolith strontium : calcium analysis. The mean growth rate of eels that had resided primarily in estuarine waters was 3.2 times greater than the growth of eels that had resided only in freshwater. Additional studies are required to clarify the life history and distributional relations of northern populations of American eels. The American eel Anguilla rostrata is a facultatively catadromous fish (Daverat et al. 2006; Jessop et al. 2008) with an Atlantic continental distribution from at least Central America to central Labrador (Helfman et al. 1987; Scott and Scott 1988). American eels support locally important, seasonal commercial fisheries at the juvenile (yellow) and sexually mature (silver) stages, with the most active fisheries occurring between the Mid-Atlantic states and the upper St. Lawrence River (Eales 1968; Jessop 1997). Elvers (early juveniles) are also fished in several states and provinces, primarily for export to Asia for culture (Jessop 1997, 1998). American eel stocks have declined in several widely distributed regions of North America (Jessop 1997; Haro et al. 2000). The American eel was designated as a species of special concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC 2006) but has not been listed as ‘‘at risk’’ under the Canadian Species At Risk Act. A status review was conducted by the U.S. Fish and Wildlife Service (USFWS 2005), but the American eel is not presently listed for protection under the U.S. Endangered Species Act (USFWS 2007). One of the difficulties in managing specific fisheries for American eels, let alone their continental population, has been the scarcity and incompleteness of life history data due to their complex, plastic life history and wide geographic range (Haro et al. 2000). Few studies exist of American eels in Newfoundland; three published studies focus on sites in eastern Newfoundland (Gray and Andrews 1970, 1971; Bouillon and Haedrich 1985), and unpublished studies examine the biology and commercial fishery for eels on the southwestern coast (Brennan 1976) and the general commercial eel fishery (Fletcher and Anderson 1973). The Newfoundland sites are among the most northerly described in the literature. This study examines American eel size and age composition, growth, maturity indices, and growth in relation to residence in freshwater and saltwater habitats at two sites in western Newfoundland, thereby extending the range of available information on the life history of American eels near their northern geographic limit and at a maximum distance from the spawning area. Such analysis may be useful for the examination of life * Corresponding author: [email protected] Received September 24, 2008; accepted February 3, 2009 Published online June 4, 2009 861 Transactions of the American Fisheries Society 138:861–871, 2009 Copyright by the American Fisheries Society 2009 DOI: 10.1577/T08-190.1 [Article]