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

Abstract

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 discuss how fishing and climate forcing interact on individual fish, marine populations, marine communities, and ecosystems to bring these levels into states that are more sensitive to (i.e. more strongly related with) 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 loss of older age classes, 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, decreasing 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. Because climate change occurs slowly, its effects are not likely to have immediate impacts on marine systems but will be manifest as the accumulation of the interactions between fishing and climate variability — unless threshold limits are exceeded. Marine resource managers need to develop approaches which maintain the resilience of individuals, populations, communities and ecosystems to the combined and interacting effects of climate and fishing. Overall, a less-heavily fished marine system, and one which shifts the focus from individual species to functional groups and fish communities, is likely to provide more stable catches with climate variability and change than would a heavily fished system

Regional warming changes fish species richness in the eastern North Atlantic Ocean

“…Perry et al 2010. Climate is changing globally, and it is likely that an increase in temperature is contributing to the increase in Lusitanian species or the decrease in Boreal species.…”

Transitional states in marine fisheries: adapting to predicted global change

“…To sustainably target fisheries developing as a result of climate, both the industry and management system will need to be made more flexible (Perry et al 2010). In the North Sea context, this requires a management system that is better able to assess and support new sustainable fishing opportunities, rather than being locked in to assessing quotas for a series of populations that provide a falling share of total catch.…”

Distribution and composition of the epibenthic megafauna north of Svalbard (Arctic)

“…Moreover, longer ice-free periods will certainly lead to an increase in human activity levels, in Arctic seas in general and the waters north of Svalbard in particular, including bottom trawling (ACIA 2004). This development will exert additional anthropogenic pressure on the marine ecosystems by either direct top-down effects of the fishery or indirect bottom-up effects by subsequent changes in trophic relationships or, most likely, the combination of both Perry et al 2010). To document such direct anthropogenic impact on the benthos, field studies are necessary to document the current status of the threatened habitats.…”