Commercial fishing amplifies impacts of increasing temperature on predator-prey interactions in marine ecosystems.

Observations of PPMR were taken from the Dapstom stomach content database (ICES 1997; Daan 1981; Pinnegar 2019). We utilised a total of 313,953 individual observations from 53,444 individual stomachs of 88 unique predator species. These observations were made on 1,862 different research hauls across the Northeast Atlantic (44° N to 79.5 ° N and 28.5 E° to 41.9° W) from 1981 to 2016. Predators were always identified to species level, with prey identified to the highest possible taxonomic level, i.e. species where possible, but often to family level. All prey species were considered (i.e. both fish and invertebrates). Fullness of stomach or level of digestibility were not considered and so the estimates of body mass may be subject to some associated uncertainty. Additional variables taken from the database included the prey abundance per predator stomach (prey count), the geographical coordinates, and the year and month each sample was collected. These variables were included in the study as any change in PPMR can be driven by multiple and not mutually exclusive processes, e.g. changes in predator body size, prey body size, predator behaviour to select different sized prey, or the behaviour of prey to avoid predation based on their body size. This data was then joined to daily sea surface temperature (SST) data (°C) from both satellite and in situ observations were extracted from the Copernicus open access data repository (Good et al., 2020). The spatial resolution of the temperature data was 0.05° longitude x 0.05° latitude and covered every month from 1981 to 2016. The average temperature (°C) was calculated per month and matched to PPMR data sampled in the following month to account for any lag effects (i.e. if a predator’s stomach contents were sampled in May 1992, then the corresponding temperature would be the monthly average of April 1992). Other environmental variables used for modelling purposes included salinity, chlorophyll (ug/l), and the average water column depth (m), which were taken from the ICES open-source data portal (ICES Data Portal, Dataset on Ocean HydroChemistry, Extracted June 12, 2023. ICES, Copenhagen). The mean of each environmental variable was calculated for each month of every year (1981–2016) and matched to the following month of PPMR data, as described for temperature. The longitude and latitude coordinates were to four decimal points. Due to spatiotemporal limitations in the environmental data layers available, 43 % of PPMR observations did not have corresponding salinity or chlorophyll data. The data was then joined to commercial fishing effort dataset. We make use of The Scientific, Technical and Economic Committee for Fisheries (STECF) trawling effort dataset because of its extensive coverage in space and time which corresponded with our PPMR observations (STECF, 2017). The STECF data provides annual fishing hours per ICES rectangle (0.5° latitude by 1° longitude) across areas of the Northeast Atlantic. We downloaded the data for the region 49.25° N to 63.25° N and 7.5° W to 12.5° E, covering the period 2002 to 2022. The data is a compilation of member state submissions in response to the Data Collection Framework (DCF) Fishing Effort Regimes Data Call in 2013 88. The STECF dataset used in this study included data from Belgium, Denmark, Netherlands, United Kingdom, France, Germany, and Sweden. Fishing effort was matched to the PPMR observations based on the year and ICES rectangle in which the sampling took place. This resulted in 131,767 PPMR observations in the Northeast Atlantic from 2002-2016 with a corresponding measure of fishing effort in hours per year (Fig. 1c). References: Daan N. Data base report of the stomach sampling project 1981. International Council for the Exploration of the Sea (1989). Good S, et al. The current configuration of the OSTIA system for operational production of foundation sea surface temperature and ice concentration analyses. Remote Sensing 12, 720 (2020). ICES. Database report of the stomach sampling project 1991 (Issue 219). . (ed Sea ICftEot) (1997). Pinnegar JK. DAPSTOM—An integrated database & portal for fish stomach records. (ed Centre for Environment FAS). 5.5 edn (2019).