Seasonal and Vertical Distribution and Growth of Juvenile and Adult Capelin (Mallotus villosus) in the St. Lawrence Estuary and Western Gulf of St. Lawrence

Abstract

The distribution of juvenile and adult capelin (Mallotus villosus) in the estuary and western Gulf of St. Lawrence was similar in 1974 and 1975. Juvenile (age 1 and 2) capelin were largely restricted to the western Gulf, which appears to serve as a nursery area for larval and juvenile capelin, throughout the summer and fall. During the summer and early fall capelin occurred in small schools which were widely distributed over most of the western Gulf. Concentration of juvenile and adult capelin into dense schools and their movement into the lower estuary in November were interpreted as the initiation of a contranatant migration to the spawning areas in the estuary. Spawning occurred first in the upper estuary (April–May) and was progressively later in the lower estuary and western Gulf. Postspawning mortality was high and resulted in a rapid decline in the abundance of adult capelin in the estuary and western Gulf following spawning. A concentration of juvenile capelin in and near the mouth of the Saguenay River throughout the year was apparently supported during the late summer by zooplankton production in the river. These fish, in turn, contribute heavily to the food resource of a large population of beluga whales that summer in the area. Capelin from the study area reach a greater mean size at the end of the 1st yr than do those from Newfoundland, Labrador, and Greenland. Subsequent growth was similar to that of stocks from southern Newfoundland but was faster than in stocks from northern Newfoundland and Labrador. Capelin populations in the estuary and western Gulf matured earlier and had younger mean ages than those from other areas in the Canadian Atlantic. Key words: capelin, Mallotus villosus, Gulf of St. Lawrence, seasonal distribution, vertical distribution, growth, spawning