Feeding ecology of autumn-spawned Atlantic herring (Clupea harengus) larvae in Trinity Bay, Newfoundland: Is recruitment linked to main prey availability?

Atlantic herring (Clupea harengus) populations in Newfoundland, Canada, are characterized by springand autumnspawning components, targeted as a mixed fishery. The spring-spawning component accounted for ~90% of the total catch until the early 2000s, but autumn-spawning herring now dominate the catch in most areas. We explored the links between recruitment of autumn-spawning herring and variability in larval prey and temperature during first winter. The main prey during the early larval stage was nauplii of the copepods Temora longicornis and Oithona similis. In the midlarval stage, Pseudocalanus sp. strongly dominated the diet. In the late-larval stage, larvae shifted to the larger calanoid copepods Calanus sp. The phenology of Pseudocalanus sp. shifted from a spring to autumn bloom during the mid-2000s, concurrent with the change of the springand autumn-spawning components. This change in zooplankton phenology suggests that conditions for herring larval survival have improved during autumn, although no significant relationships were found between recruitment and prey abundance or temperature. Our results suggest that multiple factors, rather than a single driver, interact in the regulation of herring year-class strength. Survival is the outcome of growth and mortality, making it important considering predation pressure along with prey availability in future studies.