Evidence-led Approaches to Underpin Proportionate and Sustainable Management of Inshore Fisheries: a Case Study of the Live Wrasse Fishery

Abstract

Inshore fisheries are a substantial component of the commercial fishing industry and are generally comprised of vast numbers of small-sized, adaptable vessels that target seasonally-changing, mostly non-quota resources with a wide range of gear types. Despite this, the potential ecological and social impacts of inshore fisheries are often overlooked and difficult to quantify. Monitoring and management of the sector is also complex but, as the management of inshore fisheries is shifting towards an ecosystem-based approach, understanding fishing impacts on the target species, broader marine ecosystems and other stakeholders will be key to ensuring effective decision making. In this thesis, I use recently-developed multi-species inshore fisheries for live wrasse as a case study to identify and apply approaches that could help to secure sustainable and balanced management of otherwise data-poor inshore fisheries. First, I draw together evidence of the potential population-, ecosystem- and social impacts of live wrasse fisheries. I then outline possible approaches that can be undertaken by, or in support of, resource- and time-limited management authorities. Specifically, I present a model methodology for monitoring wrasse stock abundance dynamics from fishery-dependent data collected as part of routine management in Plymouth Sound on the south coast of England, and highlight that the main drivers of variation in catches and landings vary between wrasse species. I show evidence of inter-annual declines in the stock abundance of ballan wrasse, which is likely driven by the unsustainable removal of landable individuals on the landward size of Plymouth breakwater. I then investigate variation in resource use, preferred habitat and physiology within- and between species of wrasse using stable isotope analysis. I show that there is limited inter- and intra-specific overlap in the three-dimensional isotopic niches (estimated using δ13C, δ15N, and δ34S values of wrasse muscle tissue), suggesting overall trophic redundancy and resilience among wrasse to anthropogenic disturbance is low. I also show that this variation in isotopic niche may in part be driven by interspecific variation in thermal habitat and physiology, which were estimated using δ16O and δ13C values of otolith 6 aragonite. . Finally, I set out to better understand the nature and extent of the conflicts between recreational and commercial wrasse fishers using data collected through an online questionnaire. I highlight that the inter-sectoral conflict exhibited between recreational and commercial wrasse fishers has likely arisen from negative opinions of the potential risks the commercial sector poses to the local wrasse populations and ecosystems, as well as from wider-ranging concerns (e.g. about the environmental impacts of salmon farming). Ultimately, the results presented are used to explore and recommend management options that could be adopted by fisheries managers to avoid, reduce or mitigate the identified impacts. For example, I recommend that an upward revision of ballan wrasse conservation reference sizes should be considered by fisheries management authorities to help protect spawning individuals of both sexes. Additionally, I also suggest that wrasses (particularly ballan and corkwing) should be classified as influential species within marine protected areas designated to protect reef ecosystems. Finally, I highlight the importance of the early and sustained involvement of all stakeholders in the fisheries management process to help reduce or avoid conflicts. This research is likely to provide crucial underpinnings to the Wrasses Complex Fisheries Management Plan, which is due to be prepared by the Department for Environment, Food and Rural Affairs (United Kingdom) over 2023–2025. Furthermore, the methods applied and lessons learned here, in the case study of the live wrasse fishery, can be adapted and generalised to a variety of inshore fisheries in support of a truly evidence-led and ecosystem-based future approach to fisheries management.