Temporal Variation in Size and Abundance of Juvenile Atlantic Cod (Gadus morhua) at an Inshore Site off Eastern Newfoundland

Abstract

Temporal variability in abundance and size of juvenile Atlantic cod (Gadus morhua) was studied at a shallow-water site in Trinity Bay, Newfoundland, from July 1982 to September 1983 and July 1989 to September 1990. Cod were collected with a small seine during the day and night. 0-group and 1-group cod predominated in the catch. Nighttime catches contained significantly more and larger cod than daytime catches primarily because 1-group cod were only collected at night. 1-group cod were not collected when water temperatures were less than 0 °C or when ice was present. Abundance peaked in August–November and April–June. Pelagic juveniles arrived inshore when water temperatures and salinities were highest (>12 °C, >30 ppt) in August and September and represented ~25–40 and 10%, respectively, of the cod collected at that time. Significantly more cod were collected in 1989–90 than in 1982–83, although water temperatures were not significantly different between the two periods. Sampling by additional fishing gears, including SCUBA observations, supports the hypothesis that 0-group and 1-group cod move into the sampling area at night (or dusk) and that daytime gear avoidance is secondary to diel activity patterns in explaining differences in day and night catches.