Consequences of differing definitions of maturity for management regulations of a gastropod fishery

ABSTRACT Objective The channeled whelk Busycotypus canaliculatus is the primary species in the southern New England multispecies whelk fishery and is currently overfished. Here, the definition of maturity as it pertains to size-at-maturity (L50) estimates was reassessed to update the life history traits that were determined from a decade-old stock assessment. Methods Channeled whelk were sampled in Buzzards Bay during the winter of 2021 and seasonally via commercial traps in 2022 and 2023 in three regions of southeastern Massachusetts: Buzzards Bay, Vineyard Sound, and Nantucket Sound. The specimens were dissected to assess size at maturity and life history traits. Results The data showed that reproductive development and maturity were conflated in the previous definitions of maturity and was redefined based on biological principles. The definitions of female maturity that were reported in the literature resulted in an estimated L50 of ∼89 to 105 mm shell width (SW) and ∼154–175 mm shell length (SL), whereas the revised biological definition that we used here resulted in a 28% to 42% decrease in SW (61 to 66 mm) and 26% to 37% decrease in SL (109 to 117 mm) L50. In contrast, the L50 determinations for males remained similar. Throughout this study, more males than females were collected (65 ± 10% [mean ± SD]) because the fishery has removed proportionally more females due to their larger size and higher likelihood to be above the harvestable size limit. Female gonad and nidamental gland indices peaked in the summer, which suggests that the egg cases are laid in the fall. Reproductive phenology did not differ from that which was reported in prior studies on the same populations. Conclusions The results presented here highlight the need for a more precise data-based definition of maturity for channeled whelk, as maturity classifications can drastically alter size-at-maturity estimates and fishery management decisions.