Morphometrics of American Lobster (Homarus americanus) Larvae in Relation to Stock Determinations in the Maritimes, Canada

Abstract

Morphological characteristics of the first larval stage of the American lobster (Homarus americanus) enabled the separation of the Maritime population with stepwise discriminant function analysis into three groups: the southern Gulf of St. Lawrence and its outflow around Cape Breton Island, the Atlantic inshore region of Nova Scotia, and the offshore banks bordering the Gulf of Maine. Once the effect of environmental temperature on larval size was removed, the differences between Georges and Browns banks and the Atlantic inshore disappeared. The remaining differences, chiefly in the dimensions of the second and fifth abdominal segments and the rostrum, between larvae from the Cape Breton sites and elsewhere may be due to other environmental factors or partial genetic isolation. Conservation and management practices over the past century have increased gene flow between regions, and most of this appears to be from the release of Gulf of St. Lawrence lobsters in the Gulf of Maine. A reassessment of previous studies on adult morphology, benthic movements, larval dispersal, enzyme electrophoresis, and commercial landing patterns supports the separation of the Gulf of St. Lawrence stock from the rest of the Canadian Maritimes.