Does displacement of fishing effort from marine protected areas impact the wider environment? A review and case study for displacement within the Hauraki Gulf

Abstract

Globally, the number of marine protected areas (MPAs) is increasing in hopes of addressing the declining health of the world’s oceans. One of the leading anthropogenic impacts causing this decline is the overfishing of marine species. MPAs impose a spatial restriction, with varying levels of protection, and therefore reduce once available fishing grounds. Prior fishing efforts in MPAs must either cease to exist or redistribute to new locations. This displacement of fishing effort is often raised as an argument against MPA establishment, as the movement of fishing effort is widely perceived to simply increase the negative impacts of fishing on areas outside MPAs. To investigate the relative importance of displacement of fishing effort from MPAs, this study first synthesised the current literature on studies examining the effects of fishing effort displacement from MPAs. Overall, 83 studies were found that discussed impacts that displaced fishing effort were having on biodiversity, local communities, or fishers. The majority of studies (58%) reported no negative impact of displaced effort, whereas 12% reported negative impacts arising from displaced effort, and this was seen across ecological and socio-economic factors. Some of the negative implications of displaced effort were increased costs for fishers, increased bycatch rates, impacting livelihoods, and increased degradation of benthic ecosystems. The remaining studies found displacement depended on which proposed MPA scenario was implemented. Overall, the impacts of displacement of fishing effort varied for each MPA and reinforced the concept that each MPA is unique to the environment that it is in. This study also found that the impacts of displacement seldom undermined the overall objectives of the MPAs. For the future of marine protection, this study shows that for effective management, managers need to assess the risks of displacement of fishing effort before MPA implementation. It also concluded that for a greater success of MPAs, spatial restrictions should be accompanied by a reduction in the overall fishing effort The second part of this study investigated how a newly proposed network of MPAs within the Hauraki Gulf Marine Park (HGMP), northern New Zealand, may influence fishing effort displacement. The Sea Change – Tai Timu Tai Pari marine spatial planning initiative is proposing an increase in marine protection within the HGMP from 6.6% protection to 17.6%. As the HGMP also supports the largest commercial and recreational snapper Chrysophrys auratus fishery within the country, these new MPAs may result in the displacement of this fishing effort. Fisheries data was retrieved from the Ministry of Primary Industries, and commercial and recreational snapper catches were mapped across the HGMP to see how much catch was coming from the proposed MPAs. Overall, 9.6% of commercial snapper catch in 2020/2021 and 9.1% of recreational snapper catch (2017/2018) for the whole HGMP was caught within these proposed areas. At a local MPA level, the MPAs proposed for the inner HGMP support a higher proportion of the local recreational catch due to extensive fishing effort concentrated in these zones and surrounding areas. While this may potentially mean a greater effect of displacement on surrounding areas, further research and monitoring will be needed to determine any potential effects of this displacement. Importantly whether the proposed MPAs will have a net positive or negative impact on snapper populations and surrounding fisheries, and how these compare to wider biodiversity and socio-economic outcomes. As these MPAs are set to be implemented in 2024, this study helps provide insight into the level of displacement. Overall, this thesis has discussed that fishing effort displacement from the creation of MPAs, can have impacts on wider biodiversity, communities, and fishers, but more generally observed is that there are no increasing negative impacts. This study has highlighted though that there are gaps within the current knowledge regarding displacement effects on overall net populations. Impacts of displacement should be assessed for each new MPA highlighting the need for this study’s assessment of potential snapper fishery displacement within the Hauraki Gulf. Concluding that the proposed MPAs within the Hauraki Gulf may be used as a case study to investigate displacement effects further.