Population dynamics of Arctica islandica off Long Island (USA): an analysis of sex-based demographics and regional comparisons

The boreal bivalve Arctica islandica is an important fishery in the United States (US), yet very little is known about the resiliency of this species to fishing activity due to limited understanding of localized population demographics. Demographics including age frequency, recruitment patterns, mortality rates, and sexual dimorphism were evaluated for a population sampled off Long Island (LI, 40.09658°N 73.01057°W) and compared with samples from Georges Bank (GB, 40.72767°N, 67.79850°W) collected in 2015 and 2017, where GB was described in a previous study. This study supports evidence that this species is sexually dimorphic. Earlier assumptions of prolonged lapses in recruitment were not substantiated for either the GB or LI populations; yearly cohorts were observed for the past century, and both populations presented recruitment pulses in approximately 8-y periods. Estimated ages from this study are older than previously reported for the US Mid-Atlantic with the oldest animal represented by a 310-year-old male collected from LI. Simulated total mortality was higher at GB than LI, and higher for GB females than GB males, with simulated mean longevity estimates greater at LI than GB. The population sex ratio at GB was 1:1.1 (female:male), whereas the LI ratio was 1:1.4 and relatively deficient in large females. Recruitment into the populations occurs routinely with substantial hiatuses being rare and substantive year classes occurring at least decadally with lesser, but contributing, recruitment in most years in between. Routine recruitment may insulate this species from risks posed by overfishing to an extent not typical for other long-lived species.