Two decades of no-take zones enhance lobster (Jasus edwardsii) abundance and size within marine protected areas in southeastern Australia

Abstract

Marine protected areas (MPAs) are a proven strategy for managing various stressors affecting marine ecosystems. No-take MPAs safeguard targeted species from fishing pressures, often enhancing their density, size, and biomass. Benthic species with high site fidelity, such as lobsters, have shown to benefit from such protections worldwide. This study examined the effects of MPAs on lobsters (Jasus edwardsii) within a southeastern Australian MPA network. From 2013 to 2023, we conducted fishery-independent sampling using 1065 baited pots (555 inside MPAs, 510 outside), sampling over 2000 lobsters. More and larger lobsters were caught per pot inside the MPAs (3.05 individuals/pot, 127 mm average length/pot) compared to outside (1.4 individuals/pot, 121 mm average length/pot). To assess MPA effects while accounting for habitat and environmental variability, we applied species distribution models by associating several response variables with seafloor structure (e.g., depth, seafloor complexity), oceanographic (e.g., temperature, wave energy), and protection/context (e.g., status, fishing region, MPA zone) factors. These models explained between 18 % and 75 % of the variability in the response variables with predictive accuracy ranging from 45 % to 86 %. Jasus edwardsii counts, sizes, and biomass – both overall and by sex – responded positively to MPA protection despite regional and environmental variability. Other than protection status, depth, fishing region, and MPA zone were consistently important across most models with the remaining variables showing varying influence. These findings highlight MPAs' dual role in conserving biodiversity and potentially supplementing local fisheries, with benefits that likely extend beyond their boundaries.