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

## TL;DR

Commercial fishing and rising temperatures are changing predator-prey body size ratios in marine ecosystems, potentially weakening ecosystem stability.

## Contribution

The study empirically demonstrates how fishing and warming jointly affect predator-prey body mass ratios and ecosystem stability.

## Key findings

- PPMR increases with temperature and is further amplified by high fishing effort.
- Smaller prey in warmer and heavily fished areas lead predators to target larger prey, but this doesn't counteract the overall PPMR increase.
- Higher PPMR is linked to weaker trophic interactions and reduced energy transfer efficiency.

## Abstract

Predator-prey interactions determine food web structure, energy flux, and ecosystem stability. Increasing temperatures and commercial fishing both alter body size distributions that underpin predator-prey interactions, but empirical evidence of their individual and combined effects is limited. We study how the predator to prey body mass ratio (PPMR) changes as a function of temperature and fishing effort in over 50,000 predator stomachs collected across the Northeast Atlantic over 35 years. PPMR increases with temperature, an effect that is exacerbated by greater fishing effort, driven by intraspecific decreases in prey body mass in heavily fished areas. To compensate for smaller prey (both within and across species) in warmer waters and areas of high fishing, predators target the largest prey available to them, but this is insufficient to alter the community-wide increase in PPMR. Higher PPMR is associated with weaker trophic interactions that dampen strong oscillatory dynamics but could also reduce energy transfer efficiency within ecosystems, both of which can affect ecosystem stability. These results could help underpin ecosystem-based management and sustainable fisheries by providing estimates of how future climate warming might interact with fishing to affect energy flux through marine food webs.

This study shows how commercial fishing and increasing temperatures impact predator-to-prey body mass ratios (PPMR) in the Northeast Atlantic. Authors identify an increase in PPMR that may weaken ecosystem stability, giving insight for sustainable fisheries management under future climate warming.