Signature of ocean warming in global fisheries catch

The mean temperature of the catch, an index designed to characterize the effect of climate change on global fisheries catch, increased at a rate of 0.19 degrees Celsius per decade between 1970 and 2006, showing that ocean warming has already affected global fisheries. Response of fish populations to warming In a warming climate, we would expect the rise of warm-water marine species at the expense of those adapted to cooler waters. That characteristic pattern has now been detected in a study of catch composition in 52 large marine ecosystems between 1970 and 2006, a sample that includes most of the world's major fisheries. The authors develop an index, the MTC (mean temperature of the catch), calculated from the average inferred temperature preference of exploited species weighted by their annual catch. Over these years, global temperature preference increased at a rate of about 0.2 °C every decade, and the effects were even more pronounced in non-tropical areas. Taken together, these findings highlight the need to develop adaptation plans to minimize the impacts of climate change on the economy and food security of coastal communities. Marine fishes and invertebrates respond to ocean warming through distribution shifts, generally to higher latitudes and deeper waters. Consequently, fisheries should be affected by ‘tropicalization’ of catch 1 , 2 , 3 , 4 (increasing dominance of warm-water species). However, a signature of such climate-change effects on global fisheries catch has so far not been detected. Here we report such an index, the mean temperature of the catch (MTC), that is calculated from the average inferred temperature preference of exploited species weighted by their annual catch. Our results show that, after accounting for the effects of fishing and large-scale oceanographic variability, global MTC increased at a rate of 0.19 degrees Celsius per decade between 1970 and 2006, and non-tropical MTC increased at a rate of 0.23 degrees Celsius per decade. In tropical areas, MTC increased initially because of the reduction in the proportion of subtropical species catches, but subsequently stabilized as scope for further tropicalization of communities became limited. Changes in MTC in 52 large marine ecosystems, covering the majority of the world’s coastal and shelf areas, are significantly and positively related to regional changes in sea surface temperature 5 . This study shows that ocean warming has already affected global fisheries in the past fo