Daily and seasonal spatial behaviour of waved whelk Buccinum undatum: implications for fishery management and restoration

Many marine invertebrate fisheries are vulnerable to overexploitation and require conservation measures to ensure their sustainability. In recent years, landings of waved whelk Buccinum undatum (Linnaeus, 1758) have fallen considerably along the coasts of the St. Lawrence (Canada), dropping by up to 76% in some fishing areas. Local overfishing may be explained, in part, by the species’ oviparous reproduction, which limits larval dispersion and population interactions. Using a two year long-term acoustic telemetry study, we tracked 20 individuals to assess their general movement behaviour and potential to disperse within an area. Tagged individuals displayed considerable daily movements (from a mean of 2 to 16 m/h), with no sensible differences between day and night. Both speed and habitat usage potential (HUP) varied among seasons, most likely due to the species' reproductive cycle: HUP was significantly larger during the breeding season of May (4570 m2) and June (2779 m2) than in the preceding winter months (1046 m2). Although some individuals moved over a considerable depth range, we did not observe seasonality over the bathymetric gradient of the area. Overall, the species' restricted HUP limits individual dispersal, resulting in very poor connection between neighbouring populations and making B. undatum vulnerable to local overfishing.