Morphological, Electrophoretic and Fecundity Characteristics of Atlantic Snow Crab, Chionoecetes opilio, and Implications for Fisheries Management

Abstract

For adult snow crabs (Chionoecetes opilio), from the western Gulf of St. Lawrence, eastern and western Cape Breton Island, and eastern Newfoundland, we compared morphometric, meristic, electrophoretic, and fecundity characteristics. Our morphometric, meristic, and fecundity data indicated that snow crabs from the four areas are morphologically and biologically distinct; therefore, they represent four "phenotypic" or "biological" stocks. We propose that the differences in morphology are due largely to environmental effects on growth during juvenile stages. The electrophoretic data indicate that Newfoundland and western Gulf of St. Lawrence snow crabs differ genetically from each other and from the Cape Breton Island snow crabs; therefore, they represent two different "genetic" stocks. Eastern and western Cape Breton Island snow crabs did not exhibit electrophoretic differences and, thus, they represent a single genetic stock. Genetic exchange between Atlantic Canadian snow crab populations appears possible through larval dispersal. There is a widely different degree of resilience to exploitation and response to the same management strategy between eastern and western Cape Breton Island snow crab populations; hence, a phenotypically and/or genotypically defined stock is not necessarily a useful management tool. Stocks may be subdivided into more meaningful management units that reflect intra-stock factors such as growth and recruitment patterns.

Fecundity and duration of egg incubation for multiparous female snow crabs (Chionoecetes opilio) in the fjord of Bonne Bay, Newfoundland

“…A similar relationship has been reported by Kon (1974a) and Elner and Gass (1984). Comparison with other published results is difficult, as many did not differentiate the egg developmental stage (Watson 1969;Haynes et al 1976;Thompson 1979;Davidson et al 1985) or had poor fecundity relationships due to low correlation coefficients (Elner and Gass 1984).…”

Character Discriminatory Power, Character-Set Congruence, and the Classification of Individuals from Hybrid Zones: An Example Using Stone Crabs (Menippe)

“…Morphological analysis has experienced a resurgence, as exemplified by recent interest in assessing the relative value of morphological and molecular data in constructing phylogenies and, in applied biology, in subdividing fisheries stocks (e.g., Fornier et al 1984;Davidson et al 1985;Allendorf et al 1987;Hilli's 1987;DeSalle and Grimaldi 1991;Patterson et al 1993;Thomas and Hunt 1993;Kinsey et al 1994). However, the use of morphological traits has potential shortfalls that can render the exercise phylogenetically problematic.…”

“…The efficacy of morphometries can be compromised by transient phenotypic plasticity, which allows for ecophenotypic variation that may falsely suggest hybridization between differentiated populations (Davidson et al 1985;Allendorf et al 1987;Kinsey et al 1994). Increased phenotypic variability of hybrids, mosaic character expression, or selectively mediated canalization can decrease the power of morphometries to discriminate hybrids from parentals (Lamb and Avise 1987;Carson et al 1989).…”

Distribution and Association of Larval Crabs (Decapoda: Brachyura) on the Scotian Shelf

“…opilio stocks, e.g. from the Gulf of St. Lawrence, since larval duration and surface current patterns would permit such exchange (Davidson et al 1985). Another possibility is the existence of a juvenile crab migration, counter to the direction of larval drift, which repopulates the aduPt habitat (e.g.…”