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

concentration, and pH from the Bio-ORACLE ERDDAP server (https://tinyurl.com/Bio- ORACLEv3). All variables of the Bio-ORACLE v.3.0 dataset were assessed for their reliability and accuracy through cross-validation against in-situ observation from the Global Ocean Data Analysis Project [58]. Further, we selected mean decadal projections for present-day condi- tions (2010–2019) as well as future conditions (2050–2059 and 2090–2099) under two emis- sions scenarios (SSP2-45 and SSP5-85) from the Bio-ORACLE v.3.0. dataset. Next, to analyse future changes in environmental variables across the Gulf of St. Lawrence and for each OECM, we standardized decadal changes to relative change in 2050–2059 (mid-century) and 2090–2099 (end-century) relative to the 2010–2019 (baseline). Lastly, based on percent relative change of the bottom environmental variables, we calculated the mean percent change in each variable by OECM, emissions scenario, and future timeframe. All analyses were conducted in R Studio (version 2023.12.0+369) with R 4.4.0. Spatial overlap analysis. We combined the data layers (Table 2) and the relative changes in the bottom variables to assess overall environmental changes in the Gulf and to evaluate whether potential indirect BCBs from the selected OECMs occur currently. By identifying which areas may experience the least/most environmental changes by mid-, and end-century, we also assessed whether current, indirect BCBs are likely to persist with intensifying climate change or not. Results Current OECMs and spawning habitats in the Gulf of St. Lawrence

Based on the current potential spawning habitat of Atlantic halibut, Greenland halibut, and redfish (henceforth, also referred to as focus species) were largely located in the Laurentian Channel and overlapped with current OECMs (Fig 1). 5 out of 11 OECMs (Central Gulf of St Fig 1. Overlap of current Other Effective area-based Conservation Measures (OECMs) in the Gulf of St. Lawrence with significant benthic habitats and potential spawning habitat for three demersal fish species. Significant benthic habitat includes habitat for cold-water sponges and sea pens [46, 47]; potential spawning areas include areas for Greenland halibut (Reinhardtius hippoglossoides; 50,51), Atlantic halibut (Hippoglossus hippoglossus; [49]), and redfish (Sebastes mentella, Sebastes fasciatus; [52]). Land shapefiles retrieved from http://www.naturalearthdata.com/; shapefiles for OECM outlines retrieved from [45]. https://doi.org/10.1371/journal.pone.0316754.g001 PLOS ONE Indirect biodiversity conservation in the Gulf of St. Lawrence PLOS ONE | https://doi.org/10.1371/journal.pone.0316754 January 9, 2025 5 / 20