THE GROWTH AND SIZE DISTRIBUTION OF CURRENT YEAR CLASS LOLIGO PEALEI

Area of Science:

• Marine Biology
• Fisheries Science
• Cephalopod Ecology

Background:

• Understanding population dynamics is crucial for effective fisheries management.
• Longfin inshore squid (L. pealei) are a significant component of the North Atlantic ecosystem.
• Previous studies have provided limited data on L. pealei early life stages and growth rates.

Purpose of the Study:

• To estimate the growth rate and size distribution of the current year class of L. pealei.
• To determine the selectivity of otter trawls used in L. pealei population assessments.
• To analyze the reproductive timing and patterns of L. pealei.

Main Methods:

• Daytime otter trawl collections in Menemsha Bight during the latter half of 1967.
• Estimation of trawl selectivity using 50% retention length for L. pealei.
• Application of Cassie's method for separating year classes based on size-frequency distributions.

Main Results:

• L. pealei exhibited lognormal size-frequency distributions across different age groups.
• The median growth rate for the current year class was 1.8 cm dorsal mantle length per month for the first four months post-hatching.
• Sexual maturation was observed in approximately half of the one-year-old L. pealei, with none of the current year class maturing before their first fall migration.

Conclusions:

• Egg deposition for L. pealei is temporally and spatially isolated but occurs repeatedly throughout the Vineyard Sound area from June to September.
• The growth and size distribution patterns suggest distinct recruitment events for L. pealei.
• Otter trawl selectivity for L. pealei is size-dependent, with implications for population estimates.