Evaluation of natural mortality of an unfished gastropod (Buccinum undatum) population using statolith age-frequency data in the southern Mid-Atlantic Bight

Abstract

Natural mortality estimates of harvested stocks are key parameters used in stock assessments to aid in understanding the dynamics of populations, but these estimates are difficult to obtain and have a high degree of uncertainty. Data from unfished populations, which is often rare, provide a unique and valuable opportunity to estimate natural mortality. This study provides estimates of natural mortality using multiple methods from an unfished whelk (Buccinum undatum) population using statolith ages which prove to be an accurate method to assess age of gastropods. Using statolith age-frequency data, natural mortality for this unexploited Mid-Atlantic Bight whelk population was estimated to be 0.45–0.60 year−1. Due to the unexploited state of this population, the mortality estimate in this study can be assumed to be a true reflection of natural mortality and thus compared with mortality estimates for populations under varying degrees of exploitation to understand how exploitation affects population dynamics.