Spatial ecology of black dogfish (

Abstract

Context Shark pupping and nursery grounds are essential habitats, yet these areas are undocumented for deepwater species. Young juveniles of black dogfish (Centroscyllium fabricii) were found to be dominant in the Laurentian Channel, prompting an analysis of their distribution in Canadian waters of the Northwest Atlantic. Aims This study documents patterns of distribution by sex and life stage for black dogfish in shelf and slope waters of Canada. Methods Over 40 years of trawl survey data from the Canadian Department of Fisheries and Oceans (DFO) Newfoundland and Labrador Region was analysed to document patterns of distribution of black dogfish by sex and life stage. Key results Free-swimming neonates were found in the Laurentian Channel, along with adult females, including some with pups, indicating that the Laurentian Channel is the pupping grounds for this species. Small black dogfish, highly abundant in the Channel, is largely absent in slope waters, indicating that the Channel is the nursery ground for black dogfish in Canada. Conclusions As they grows, black dogfish individuals undergo a multi-year distributional shift extending over ∼4000 km, originating in the Laurentian Channel out to slope waters, with the largest fish being found furthest from the Channel. No other deep demersal chondrichthyans are known to undergo a progressive migration as they grow, more akin to pelagic sharks where separate pupping–nursery grounds and long-distance migrations are commonly documented. Implications The segregation by life stages shown in the present study differs from previously reported distribution patterns of black dogfish in Greenland and Iceland. Given warm and stable ambient temperatures in the Channel, similar to slope waters, black dogfish is stenothermal, maintaining a narrow thermal profile throughout its life. Identifying the essential habitats of pupping and nursery grounds is crucial to the management and conservation of this species.