Abstract
AbstractAlewife Alosa pseudoharengus is an anadromous clupeid fish of long‐standing ecological and socioeconomic importance along the Atlantic coast of North America. Since the 1970s, Alewife populations have been declining throughout the species’ range. A number of hypotheses have been proposed to explain the decline, but a lack of basic information on population demographics inhibits hypothesis testing. In this study, we evaluated the use of morphometric analysis to discriminate among spawning stocks of Alewives collected from 24 sites in Maine and one site in Massachusetts. We first identified 10 morphometric measurements that were not influenced by the freezing–thawing process, and then used principal component and discriminant function analyses to develop stock‐structure classification models from these 10 measurements. Classification models were able to discriminate Alewives to be from Maine or the single Massachusetts site 100% of the time. In addition, classification models correctly classified pooled sampling sites from the extreme western and eastern parts of Maine with 64% accuracy. Morphometric analysis may therefore provide an easily accessible, comparatively fast, and inexpensive method to discriminate marine‐captured Alewives spawned in areas separated by major biogeographic regions, large geographic distances (100s of kilometers), or both, and thus help inform questions about stock composition at these spatial scales for assessment surveys and bycatch events.Received March 30, 2012; accepted October 14, 2012.
Highlights
IntroductionCommercial catch of Alewives and Blueback Herring Alosa aestivalis (collectively known as “river herring”) has declined, starting with a sharp drop in the 1970s and a more recent drop to very low levels since the mid-1980s (Fay et al 1983; Schmidt et al 2003)
Alewife Alosa pseudoharengus is an anadromous clupeid fish of long-standing ecological and socioeconomic importance along the Atlantic coast of North America
Fork length (FL) and total length (TL) were measured to the nearest millimeter and total mass was recorded to the nearest gram
Summary
Commercial catch of Alewives and Blueback Herring Alosa aestivalis (collectively known as “river herring”) has declined, starting with a sharp drop in the 1970s and a more recent drop to very low levels since the mid-1980s (Fay et al 1983; Schmidt et al 2003) Because of this decline, the U.S National Marine Fisheries Service listed river herring as a Species of Concern (NMFS 2009). Alewives are believed to return to their natal river systems and lakes to spawn (Thunberg 1971) This behavior, over time, may lead to unique characteristics based on the influence of local environments on early life stages (Beacham et al 1988; Taylor 1991). Such characteristics provide an opportunity to test for stock structure based on natal origin if adaptations to local river and lake conditions are expressed as measurable differences in phenotypic traits (Barnett-Johnson et al 2008)
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