Increasing spillover enhances southern California spiny lobster catch along marine reserve borders

Abstract

The conservation benefits of marine reserves are well established but their contribution to adjacent fisheries via spillover is less certain and context‐dependent. Theoretical predictions do not always match empirical evidence from individual reserves, so carefully designed studies are essential for accurately assessing spillover and its contribution to fisheries. Biomass buildup within reserves, and spillover from reserve borders, also usually takes time to develop. In 2003, a network of no‐take marine reserves was established in the Northern Channel Islands (NCI) of southern California (CA) to conserve biodiversity and to eventually enhance local fisheries through spillover of larvae, juveniles, and adults. The reserve network impacted the local CA spiny lobster (Panulirus interruptus) fishery by removing about 20% of fishing grounds in the NCI. In 2008, a collaborative fisheries research effort detected substantial lobster population increases within reserves, and an indication of the possible spillover of adult lobsters across reserve borders. To estimate whether and how much populations within reserves, and spillover from reserves, have increased through time, we repeated the sampling program 10 years later in 2018 at two of the three original reserves. Scientific trapping was conducted prior to the fishing season along a spatial gradient beginning deep within the reserves to reference sites located outside (≥2 km) of reserve borders. Results showed that legal‐sized lobster abundance in traps (catch per unit effort) increased by 125%–465% deep inside reserves, and by 223%–331% at sites near to reserve borders, and by nearly 400% just outside of reserve borders over the 10‐year period, thus indicating a substantial increase in spillover across reserve borders. A similar pattern was observed in lobster biomass caught in traps at the two reserves. This study demonstrates how spillover scales with biomass buildup and that collaborative fisheries research can be used to assess the efficacy of marine reserves as fishery management tools worldwide.

Regional differences in fishing behavior determine whether a marine reserve network enhances fishery yield

“…Our prior work showed increases in spiny lobster abundance within two reserves located in one shing block in the northern region, and the related spillover of legalsized adult lobsters, as well as enhanced lobster catch and CPUE in that shing block relative to nearby blocks without reserves 21 . Prior research also revealed that lobster shers often concentrate their trapping effort near reserve borders 21,28,29 , in part due to the shers participation in collaborative research with scientists and awareness of its results 22,30 . We reasoned that differences in yield between the north and south regions associated with the establishment of the MLPA reserves could be explained by differences in shing behavior between the two regions, speci cally the degree to which shers in each region shed near reserve borders early in the shing season (October-November) when landings are by far the highest.…”

“…Regional differences in shing behavior that altered the effectiveness of reserves on shery yield may also re ect cultural differences in addition to environmental differences. Beginning in 2003, we developed a collaborative shery research program in the northern region of the shery to assess the effects of marine reserves on lobster populations, spillover, and shery yield 21,22,30 . Our collaboration relied on research trapping campaigns with shers as well as numerous formal and informal meetings with members of the California Lobster and Trap Fisherman's Association (CLTFA) and the CA Department of Fish and Wildlife (CDFW), at which our results pertaining to the responses of lobster populations to reserve protection were discussed.…”

“…Statistical analysis of marine reserve data also found that spillover of adult target species is a relatively common phenomenon, but modelling of those data indicated spillover was not su cient to sustain depleted sheries 17 . By contrast, results from eld studies have shown that spillover of adults can enhance local catch in depleted sheries [18][19][20] , and at least in one case a sustainable, well-managed shery [21][22][23] .…”

Marine protected areas promote resilience of kelp forests to marine heatwaves by preserving trophic cascades

“…Larger individual biomass of overexploited species is expected inside fully protected MPAs, and these larger animals are usually more efficient at consuming larger urchins . Having such estimates for spiny lobsters in this study could help us to further understand the role of spiny lobsters in trophic cascades, although spillover effects of lobsters in both abundance and biomass have been demonstrated previously (Lenihan et al, 2022). Moreover, we did not include in our analyses other smaller species, such as crabs, which may benefit from MPAs and influence urchin populations by feeding on their juveniles (Clemente et al, 2013).…”

Introduction: Honoring the contribution of Charles H. Peterson (1946–2020) to the field of marine ecology

“…Paxton et al (2022) provide a framework for better incorporating ecological principles, adaptive management, and experiments in the siting, design, construction, and evaluation of artificial reefs in the coastal ocean. To wrap up the Special Feature , Smith et al (2022) and Lenihan et al (2022) report on the ecological impacts of fishing and the use of marine reserves and collaborative fishery research in recovering, restoring, and managing coastal marine fisheries. In summary, the papers in our Special Feature represent a great tribute to the legacy of Charles H. Peterson and are research contributions that would have made him proud.…”