Ocean quahog (Arctica islandica) growth rate analyses of four populations from the Mid-Atlantic Bight and Georges Bank

Abstract

Growth rates from 1480 Arctica islandica from New Jersey, collected in 2019 from north and south of the Hudson Canyon, were analyzed and compared to animals obtained from Long Island and Georges Bank. New Jersey represents the southern portion of the A. islandica stock in the Mid-Atlantic Bight, and animals here may experience warmer temperatures compared to their northern counterparts. Arctica islandica from New Jersey have slower maximum growth rates compared to northern A. islandica, particularly from Georges Bank; however, A. islandica from south of the Hudson Canyon have higher growth rates at older ages compared to the other three sites. Growth rates have been increasing over the past three centuries, potentially due to increasing bottom water temperatures, with time to maturity and time to commercial size drastically decreasing, leading to fewer years for reproduction prior to recruiting into the fishery. Three growth models, von Bertalanffy, Tanaka, and modified Tanaka were examined for goodness of fit to growth data. The von Bertalanffy, commonly used in fisheries management, had the worst fit for all populations, males and females, and at all 20-year cohort groups, and should not be used in the management of this species. The Tanaka and modified Tanaka models are recommended in its place, as these models best fit A. islandica growth at young (Tanaka) and older (>160 years, modified Tanaka) ages.