Assessing size at sexual maturity and fine-scale population structure in a direct developing whelk (Buccinum undatum) in Southern Newfoundland, Canada

Buccinum undatum (waved whelk) is a neogastropod with several small-scale commercial fisheries in Atlantic Canada. Whelks are vulnerable to overfishing, partly because they lack a pelagic larval phase. To date, no studies in the Northwest Atlantic have synthesized demographic and genetic data to explore the species' biology at a fishery relevant scale. We quantified patterns of genetic structure in whelks within both the Northwest Atlantic Fisheries Organization subdivision 3Ps fishing zone and in the broader Northwest Atlantic, and estimated length at first maturity (L50) of 3Ps whelks. Genetic structure estimates were low, indicating one genetic population within 3Ps, with subtle but significant differentiation across the Northwest Atlantic. L50 was 64.0 mm and 69.9 mm for males and females respectively and above the regional minimum legal size of 63 mm. Our results suggest that separate regional management of Northwest Atlantic fisheries is appropriate. Within 3Ps, whelks are genetically well-mixed, but the implications for population persistence and management remain unknown. To safeguard the stock in the face of continued fishing, further assessments of demographic traits are warranted.