Life History of American Eels from Western Newfoundland

Abstract

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 = −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 = −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.