Trends in larval densities, spawning timing, and site quality of capelin (Mallotus villosus) across bays and habitats in Newfoundland, Canada

Capelin is a short-lived forage fish species that underwent a population collapse in 1991 on the Newfoundland and Labrador Shelf, Canada (Northwest Atlantic Fisheries Organization Divisions 2J3KL) and has not recovered. The collapsed stock is characterized by delayed spawning timing and low recruitment. As year-class strength is set early in life, long-term larval monitoring at an intertidal spawning site in Trinity Bay (TB) is used as a proxy for stock-wide recruitment. Capelin spawn at both intertidal and subtidal habitats; however, there is minimal larval information from bays with a high incidence of subtidal spawning. We aimed to (i) compare inter-annual trends in temperatures, timing of spawning, and annual larval densities between two northeastern bays [TB and Notre Dame Bay (NDB)] and (ii) compare habitat quality metrics and larval densities between subtidal and intertidal sites in NDB. The date of first spawning in TB and NDB was positively correlated, suggesting that years with delayed spawning are experienced shelf-wide. While larval density was lower in NDB compared to TB, inter-annual trends were similar. In NDB, larval densities at both intertidal and subtidal spawning habitats were similar within a year, but temperatures and the proportion of dead eggs were lower at subtidal sites. These habitat quality metrics, however, were not related to annual larval density. These findings improve our knowledge on sources of capelin productivity, including the potential importance of subtidal spawning to recruitment dynamics.