The waved whelk (Buccinum undatum) is commercially fished in the North Atlantic Ocean; the fishery is growing in Atlantic Canada. The species’ oviparous reproduction limits dispersal, posing a challenge to fishery management at the meta-population level. The Minimum Landing Size (MLS) for B. undatum in Nova Scotia is set at 65 mm with intent to maintain an adequate spawning stock. The implicit assumption that the MLS approximates a size at which half the population has reached reproductive maturity (LM50) is unjustified. We measured the LM50 of the whelks sampled from commercial fishing catches during 2016 and 2017 at five sites on the Eastern Scotian Shelf located roughly 11–210 km apart. There were significant differences among all measured parameters including total shell length, LM50, sex ratio and parasitic prevalence. The latter was measured to investigate its effects on calculations of LM50 and fishery regulations. The LM50 was smaller than the MLS at all sites. The LM50 for males ranged 45–64 mm, and 53–65 mm for females. The age at LM50 was found to be consistent with other studies: 5–6 years for both sexes. The size-frequency distributions in most samples were approximately normally distributed. The sex ratio was within the range found in other studies but varied among sampling sites. The prevalence of castrating trematodes was found to be 2–26% in males and 5–25% in females. We suggest that the area-based, effort management model for the fishery should adopt locale-specific MLS values based on the LM50 determined for sub-populations being exploited within specific areas of fishing access.
