In the absence of detailed knowledge on how fish species will respond to climate change, simple macroecological approaches can be usefully employed to investigate the potential impacts on production of marine ecosystems across a body size range typically encompassing mesozooplankton and fish larvae up to the largest predatory fishes. Statistical models can be used to establish relationships between observed primary production and fishery yields. Simple theory based on the transfer of energy from smaller to larger organisms and temperature dependence on metabolic rates can be used to predict the static abundance-body size distribution from primary productivity and temperature. Dynamic size spectrum models allow for time-dependent processes to be taken into account and testing effects of different fishing scenarios on the size spectrum.
Results/Conclusions
Using a coupled physical-biogeochemical model, climate-mediated changes in primary productivity and temperature were modelled for 20 large-marine ecosystems around the world under past and far-future climate change scenarios. This information was used to force a static size-based scaling model and a dynamic size spectrum model to estimate the potential abundance-size distributions of marine predators, across size ranges that are typically dominated by fish and squid. The dynamic size spectrum model is then used to investigate the effects of different size-selective fishing strategies on potential yield of the overall system. We compare potential production estimates from both size-based models in the absence of exploitation to present day observed catches of small pelagic, demersal and large pelagic fishes and discuss the potential implications for fisheries in the future.