Using benthic recruitment densities to forecast fisheries recruitment of American lobster in Atlantic Canada

Abstract

There is limited understanding of the mechanisms underlying the marked spatial and temporal trends in landings of American lobster in Canada since the mid 1980’s, and little ability to forecast changes. We built an individual-based model for three Lobster Fishing Areas (LFAs) in Canada that uses the annual density of benthic recruits in nursery grounds to generate an index of exploited biomass 6 to 10 years in the future, using von Bertalanffy growth equations complemented with inter-individual variability in growth, and regional maturity ogives and spawning probabilities to allow exclusion of ovigerous females from the exploitable biomass. We found significant positive relationships between the modelled biomass index and fisheries landings in all three LFAs. Out-of-sample validation in two LFAs (longer time series) using 1-year and 6-year reduced data sets revealed mean annual prediction errors of 11.4% and 11.2%, and 23.7% and 51.7%, respectively. Our findings strongly suggest benthic recruitment indices could help make strategic decisions concerning lobster fishing activities, and they argue for the continued and expanded monitoring of lobster benthic recruitment in Canada.