Publication Abstract

Predator-prey interactions determine food web structure, energy flow, 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 studied how the predator to prey body mass ratio (PPMR) changed as a function of temperature and fishing effort in over 50,000 predator stomachs collected across the Northeast Atlantic over 35 years. PPMR increased with temperature, driven by intraspecific decreases in prey body mass – effects that were exacerbated by greater fishing effort. To compensate for smaller prey species in warmer waters and areas of high fishing, predators targeted fewer species of relatively large prey, but this was insufficient to alter the community wide increase in PPMR. Higher PPMR is associated with weaker trophic interactions that dampen 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 by providing estimates of how climate warming interacts with fishing to affect energy flow through marine food webs.

Amy L. Shurety, Murray S. A. Thompson*, Elena Couce*, Tom C. Cameron and Eoin J. O’Gorman