Abstract

Marine ecosystems support human life in multi-faceted ways and are depended on for food and income by many coastal communities. However, marine habitats are being altered by anthropogenic pressures, influencing the diversity and distribution of species, including species that are relied upon by commercial fisheries. Destructive fishing practices such as dredging and trawling can have adverse impacts on the seabed and associated species through the degradation and fragmentation of benthic habitats. Spatial management of marine areas is required to mitigate impacts, with Marine Protected Areas (MPAs) being advocated as tools that can not only protect and restore biodiversity but also improve fisheries sustainability and protect fisher livelihoods. The levels of protection vary and many MPAs are feature-based in that they only restrict damaging activities from specific evidenced conservation features within their boundaries. MPAs that exclude bottom-towed fishing from all habitats within their boundaries, a form of whole-site MPA designation, have shown benefits in terms of increased biodiversity and biomass beyond the benefits demonstrated by feature-based MPAs. In Jersey, Channel Islands, two offshore MPAs that are managed following the whole-site approach were designated in 2017. This provided an opportunity to assess both ecological and socio-economic outcomes of this form of marine 8 management. The objectives of MPAs relate to both conservation and fisheries but the impact of spatial management changes on local fisheries is rarely captured in post MPA designation monitoring, despite social and economic factors being known to influence the success of a MPA. To date, fishing impacts on rocky reef habitats have been the focus of ecological MPA research, while the impacts of fishing on mixed sediments that also support biodiversity have received less attention. Firstly, this thesis aims to add to the understanding of socio-economic impacts through engagement with the local fishing fleet to understand impacts to fishers’ livelihoods; and secondly it aims to address the ecological knowledge gap regarding the response of mixed sediments following the exclusion of bottom-towed fishing through a combination of survey methods (baited video, towed video, and grab surveys), both inside and outside the MPAs. For the key commercial fishery species (lobster, Homarus gammarus; brown crab, Cancer pagurus; spider crab, Maja brachydactyla; scallop, Pecten maximus; and whelk, Buccinum undatum), multiple habitats in Jersey’s waters were found to contribute to their annual economic value to Jersey fisheries (~ £7.5 million). Also identified is the strong economic dependence of local fishers on shellfish, particularly crab and lobster, as the majority of the fleet comprises static potting vessels. However, the MPAs had yet to have a noticeable benefit in terms of increased catch or improved fisher wellbeing. Ecologically, it was found that mixed sediment habitats, such as those targeted by bottom-towed fishing practices, had greater numbers of mobile and infaunal taxa inside the MPAs compared to Open Controls. Although for infaunal taxa, this was only statistically significant for the oldest MPA surveyed. This highlights the importance of MPA age, especially when considering ecological success. Within the MPAs there was no increase in the abundance of any of the key commercial 9 crustacean species (lobster, brown crab and spider crab). This may have been related to the continuation of static fishing within the MPAs. Emphasised in this thesis is the importance of considering species’ life histories and their habitat requirements in management plans. Also discussed is the need for further spatial management of fisheries outside of the current MPAs and the introduction of gear limits within the MPAs to secure sustainable fishing livelihoods. Critically, this research provides the first insight into species assemblage composition, diversity and abundance in response to the exclusion of bottom-towed fishing across a range of sedimentary habitats and the results could be used to better inform future MPA management.

Document Type

Thesis

Publication Date

2022-01-01

DOI

10.24382/983

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