Assessing indirect biodiversity conservation benefits of fisheries closures in the Gulf of St. Lawrence, Canada

which are ideally climate-informed, reflecting both the primary and indirect BCBs need to be developed and directly integrated across OECMs design, monitoring and management [11]. This way, a more comprehensive understanding of the effectiveness, functionality and rele- vance, as well as climate change vulnerability to help adapt management can be achieved [73]. Examples of biogeochemical ecosystem indicators include temperature, oxygen concentration, pH, and primary productivity. Ecological ecosystem indicators should include the biomass of species related to primary and indirect BCBs [23, 74], such as cold-water coral cover, sponge cover or redfish biomass. Our study represents one approach in integrating available data and knowledge about the ecosystem protected by OECMs in the Gulf of St. Lawrence, to assess BCBs now and with ongoing climate change. This approach could be translated into a stan- dardized ecosystem indicators for the region, by, for example, providing integrated impact maps on a regular schedule, such as shown in Fig 4. Finally, targeted and adaptive improvement of OECMs in Canada and other regions of the world will rely on understanding of climate vulnerability by species and by region [75]. Conse- quences, climate vulnerability assessment need to become a key component in OECM desig- nation and evaluation under current and future climate change. Our approach represents one among several approaches [75], where we specifically aimed at filling the gap of matching management and assessment needs in terms of temporal and spatial scale, hence, moving

towards operationalizing climate vulnerability assessments for OECMs. Limitations and outlook Our assessment has its limitations in terms of data availability, species focus, and uncertainty in the applied climate change projections of the environmental variables. Data limitations—the data of potential spawning habitat of Atlantic halibut, Greenland hal- ibut and redfish are based on various sampling and tagging studies that only cover 2–5 years that are not overlapping. While this is the currently available data on these specific spawning behaviours in the region, longer time frames would give a better estimate of current spawning habitats and their variability in the Gulf. This underscored the above-mentioned necessity of continuous ecosystem monitoring of OECMs, where, for example, depth-integrated ichthyo- plankton sampling could provide data on larval distribution and density within a given region. While this has been challenging for species that reproduce in the winter due to seasonal ice- cover in the Gulf, climate warming has already and is expected to continue to reduce ice-cover in the Gulf in the future [76], providing a wider sampling window. Our analysis is based on knowledge from peer-reviewed literature and government publica- tions. While these sources provide evidence of e.g., current and future changes in the bottom environment of the Gulf of St. Lawrence or larval density of specific fish species, local knowl- edge and Indigenous knowledge can provide additional evidence of ecosystem status and

changes within OECMs in Canada [25, 77]. This is further relevant, as the Aichi Biodiversity Targets of the Convention on Biological Diversity’s Strategic Plan for Biodiversity acknowl- edge Indigenous stewardship for areas outside of protected areas, such as OECMs [78]. Here, the Indigenous Circle of Experts in Canada stipulated these areas as Indigenous Protected and Conserved Areas that are Indigenous led with a long-term commitment to biodiversity conser- vation [77]. Species focus—We focused on three groundfish species in our assessment of indirect BCBs of the OECMs in the Laurentian Channel. This focus was due to the recent findings of poten- tial spawning habitats in of the three groundfish species in the Laurentian Channel [49, 51, 52], as well as their economic contribution to the fishing industry in the region [79]. We assumed a positive impact on their spawning habitat in the Gulf of St. Lawrence due to the PLOS ONE Indirect biodiversity conservation in the Gulf of St. Lawrence PLOS ONE | https://doi.org/10.1371/journal.pone.0316754 January 9, 2025 13 / 20