MEPS prepress abstract   -  DOI: https://doi.org/10.3354/meps14766

ABSTRACT: Fishing is often concentrated near marine protected area (MPA) boundaries due to expectations of greater catch-rates associated with the ‘spill-over’ of adult individuals. This fishing is known to reduce populations near boundaries, but our understanding of the long-term sustainability of this harvest remains limited. Over the last 25 yr, the spiny lobster Jasus edwarsii has experienced serious declines within north-eastern New Zealand MPAs. Prior to reductions, commercial fishers concentrated effort on offshore boundaries targeting lobsters undertaking seasonal offshore movements. While this spill-over highlighted the success of these MPAs, it also indicated they were too small to encapsulate seasonal movements. In recent years fishers rarely target this area, and the extent to which lobsters move offshore is unknown. To evaluate connections between this spill-over harvest, population declines and changes in seasonal movements, potting-surveys were conducted over 2018-2019 to examine seasonal shifts in population distribution. During 2018-2019, seasonal changes in habitat were evident, but mostly constrained to coastal-reef habitat, with ~5% caught offshore of reef, and only one individual caught beyond offshore boundaries. Comparison with commercial-catch data from reserve boundaries from 1994–1997 revealed reductions in abundances and changes in size and sex of lobsters caught offshore. In contrast to 1994–1997, only large males were caught offshore of reef habitat. At low densities, small and female lobsters may be maintaining greater association with protective-reef structure. The historic offshore boundary spill-over harvest reflected offshore movements at high population densities but likely contributed to population declines. This in turn altered the extent lobsters move offshore and inevitably closed this spill-over pathway.