Spatiotemporal dynamics of effective fishing effort in the American lobster (Homarus americanus) fishery along the coast of Maine, USA

Abstract

Utilization and interpretation of fishery-dependent data such as fishing effort, although important in quantifying the dynamics of a fishery, tend to be challenging due to non-random sampling and the complexity of quantifying a species’ interaction with complex effects of environmental factors. We developed a framework for estimating effective fishing effort from fishery-dependent sampling data for the coastal Maine American lobster (Homarus americanus) fishery, where a lack of high resolution effort data does not permit sufficient understanding of fishery dynamics. This framework incorporates environmental covariates in a bootstrapped two-stage generalized additive model to standardize lobster catch per unit effort (CPUE) from 2006 to 2013. Estimated confidence intervals (CIs) of sub-regional standardized CPUE were combined with congruent resolution landings data to estimate CIs of effective effort. Both effort and landings varied seasonally, with the peak of effective effort consistently preceding the peak of landings. Coast-wide from 2006 to 2013, effective effort increased modestly (4.6%) while landings increased dramatically (69.6%), suggesting assessment of spatiotemporal fishery dynamics may provide important insights for future management. Characteristic northeast-southwest differences in catch and effort suggest spatial non-stationarity of biological, temporal, and geographic processes in the Maine coastal American lobster fishery. The approach developed in this study has utility in situations in which a fishery may be data-limited, or with a surplus of fishery-dependent data.