Oral Presentation Australian Society for Fish Biology Conference 2024

Reconsidering the impossible: a size-based approach to the recruitment potential of larval and juvenile Pacific hake (Merluccius productus) (111169)

Iain M Suthers 1 , Charles Hinchliffe 1 2 , Hayden Schilling 3 , Erica Mason 2 , Andrew Thompson 2 , John Field 2 , Pierre Pepin 4 , Daniel Falster 1
  1. Ecology & Evolutionary Research Centre,, University of New South Wales, Sydney, NSW, Australia
  2. Southwest Fisheries Science Centre,, NOAA, La Jolla, California, USA
  3. NSW Department of Primary Industries, Port Stephens Fisheries Institute, Nelson Bay, NSW, Australia
  4. Northwest Atlantic Fisheries Centre, Fisheries and Oceans Canada, St. Johns, Newfoundland, Canada

Forecasting interannual variability in the supply of young fish to the fishery remains a significant problem after 100 years. A comprehensive metric of larval success is the interaction of growth (G) and mortality (M), sometimes referred to as the recruitment potential. Both M and G require estimates of age, arduously obtained from daily growth increments, at fine spatial and temporal scales. However, we have recently shown that the descending slope of the size-frequency distribution of a growing population is a robust measure of the M/G ratio, without having to age the larvae. We applied this method to larval surveys of Pacific hake, from the California Cooperative Fisheries Investigations winter surveys, between 1978-2021 where eight strong year classes appeared in the fishery. The annual average larval M/G, based on the size distribution, was not correlated with the subsequent fishery year class strength, estimated from the age-specific harvest. There was however, a weak positive correlation using spring surveys of pelagic juvenile hake (2005-2021). Routinely incorporating the competing effects of growth and mortality for the first time will re-invigorate fisheries oceanography, particularly with regard to the ephemeral coastal features, adjacent to substantial coastal fisheries.