Spilling over deepwater boundaries: evidence of spillover from two deepwater restricted fishing areas in Hawaii

The net export of adults (spillover) is an important though contentious benefit of marine protected areas (MPAs). Controversy over spillover often exists because it is difficult to discern empirically. In addition, of those studies that have provided empirical evidence, nearly all are from shallow reef ecosystems. Here we examined 2 deepwater MPAs in the main Hawaiian Islands, established to benefit a complex of species called the 'Deep 7.' To study these fishes, we used baited cameras and commercial fishery data. Relative abundance, fish size, and species richness observed using camera data declined with distance from MPAs, signifying that species had begun to spill over the MPA boundaries into fishing grounds. Further, temporal analyses of these spatial trends indicated that they did not always exist but developed in the fifth and sixth years of sampling. Changes in fish size over time supported these results, with asymptotes in fish size seen inside and increases seen outside MPAs in the fifth and sixth years of sampling. Displaced fishing effort may have also caused initial declines in Etelis coruscans size and catch data that increased in later years. Further, low sample sizes and public announcements prior to sampling in Year 8 may have contributed to the decline in E. carbunculus sizes inside, and spatial trends outside, an MPA that were no longer significant in Year 8. Identifying the ability and time span for an MPA to begin to benefit a fishery and how quickly fishing may remove those benefits is crucial to resolving debates regarding the use of MPAs in fisheries management.