Publication abstract

Sensitivity of marine systems to climate and fishing: concepts, issues and management responses

I.R. Perry, P. Cury, K. Brander, S.Jennings*, C. Mollmann and B. Planque

Modern fisheries research and management must understand and take account of the interactions between climate and fishing, rather than try to disentangle their effects and address each separately. These interactions are significant drivers of change in exploited marine systems and have ramifications for ecosystems and those who depend on the services they provide. We demonstrate how fishing and climate forcing interact at the levels of the individual, population, community, and ecosystems to bring these levels into states that are more sensitive to climate forcing. Fishing is unlikely to alter the sensitivities of individual finfish and invertebrates to climate forcing. It will remove individuals with specific characteristics from the gene pool, thereby affecting structure and function at higher levels of organisation. Fishing leads to a reduction in age-structure, spatial contraction, loss of sub-units, and alteration of life history traits in populations, making them more sensitive to climate variability at interannual to interdecadal scales. Fishing reduces the mean size of individuals and mean trophic level of communities, increasing their turnover time leading them to track environmental variability more closely. Marine ecosystems under intense exploitation evolve towards stronger bottom-up control (and greater sensitivity to climate forcing) as a result of decreases in populations of top predators which promotes increases in prey species with faster turnover rates. Because it occurs more slowly, the effects of climate change are not likely to have immediate impacts on marine systems, but will be experienced as the accumulation of the interactions between fishing and climate variability. Managers need to develop approaches which maintain the resilience of individuals, populations, communities and ecosystems to these combined and interacting effects of climate and fishing. Priority should be given to maintaining broad population age and size structures and ensuring that genetically distinct and/or spatially defined population subunits are not extirpated. Such actions would lead to systems that are less likely to undergo sudden modifications in structure and will remain productive under the dual perturbations of climate forcing and fishing.

Reference

I.R. Perry, P. Cury, K. Brander, S.Jennings*, C. Mollmann and B. Planque (2010) Sensitivity of marine systems to climate and fishing: concepts, issues and management responses. Journal of Marine Systems 79; 403-417