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

extend beyond the ecological sphere, highlighting consequences OECM policy and manage- ment. As the environment continues to change, adaptive management will be crucial to ensur- ing that OECMs remain effective in fulfilling their conservation objectives [23]. Through this study, we aim to contribute to a deeper understanding of the role of OECMs in marine biodi- versity conservation and to provide insights that can inform future conservation efforts in the face of a changing climate. Material and methods Knowledge and data layers We synthesized data sources on eight selected OECMs, associated species, and variables for the bottom environment in the Gulf (details on the specific data sets and their respective sources are in Tables 1 and 2): (i) marine conservation management—spatially explicit bound- aries and properties of current significant benthic habitats and OECMs; (ii) species tracking and geolocation modeling for Atlantic halibut (Hippoglossus hippoglossus); (iii) systematic field sampling and DNA identification of Greenland halibut (Reinhardtius hippoglossoides); (iv) sys- tematic field sampling of redfish larvae (Sebastes spp); (v) life-history parameters in terms of preferred temperature ranges for non-spawning and spawning adults of Atlantic halibut, Greenland halibut, and redfish; (vi) High-resolution, future climate change projections of bot- tom temperature (˚C), bottom oxygen concentration (mmol m-3), and bottom pH, under two climate change emissions scenarios, Shared Socioeconomic Pathways (SSPs)—SSP2-45 and

SSP5-85. We selected these particular variables due to their associations with the geographic distribution and life-history traits of demersal species, including spawning locations and suc- cessful completion of early life stages (e.g., [15, 17, 41–43]). The two pathways, SSP2-45 and SSP5-85, translate to moderate to extreme changes in the three bottom environment variables: Table 1. Overview of Other Effective Conservation Measures (OECMs) in the Gulf of St. Lawrence included in this study with direct and indirect biodiversity con- servation benefits (BCBs). ID OECM Appr. Size [km2] Av. Depth ± St.Dev [m] Direct BCB Indirect BCBs Reference 1 Beauge´ Bank Sponge Conservation Area 215 86.63 ± 9.86 Cold-water corals Protection of habitat used by fish and invertebrates. [30] 2 Central Gulf of St Lawrence Coral Conservation Area 1,284 405.81 ± 14.64 Sea pens [31] 3 East of Anticosti Island Sponge Conservation Area 939 132.35 ± 26.35 Cold-water corals [32] 4 Eastern Gulf of St Lawrence Coral Conservation Area 423 462.02 ± 17.45 Sea pens [33] 5 Eastern Honguedo Strait Coral and Sponge Conservation Area 2,338 366.12 ± 22.46 Cold-water corals & Sea pens [34] 6 Jacques-Cartier Strait Sponge Conservation Area 346 97.87 ± 18.56 Cold-water corals [35] 7 North of Bennett Bank Coral Conservation Area 821 401.54 ± 25.35 Sea pens [36] 8 Parent Bank Sponge Conservation Area 530 122.91 ± 40.86 Cold-water corals [37] 9 Slope of Magdalen Shallows Coral Conservation Area 335 388.79 ± 19.23 Sea pens [38] 10 South-East of Anticosti Island Sponge

Conservation Area 845 357.96 ± 34.28 Cold-water corals [39] 11 Western Honguedo Strait Coral Conservation Area 496 377.93 ± 6.64 Sea pens [40] https://doi.org/10.1371/journal.pone.0316754.t001 PLOS ONE Indirect biodiversity conservation in the Gulf of St. Lawrence PLOS ONE | https://doi.org/10.1371/journal.pone.0316754 January 9, 2025 3 / 20