Mean Temperature of Catch Shows Impact of Ocean Warming on Fisheries

by Hannah Tannenbaum

Understanding the impact of climate change on marine fisheries viability has important implications for the sustainability of the industry. Cheung, Watson and Pauly (2013) collected catch and supplemental data, and computed mean temperature of catch, MTC from average inferred temperature of over 900 species of exploited fish weighted with their annual catch rates. MTC was inferred from modeled distributions for the years 1970 to 2006. It was shown that there is a positive relationship between increased rate of SST change and increases to MTC, and that global fisheries have responded with ‘tropicalization,’ shifts.

Climate change is predicted to have a broad variety of effects on marine fisheries distribution, phenology, and ecological implications including studies which have shown increased vulnerability of some fisheries. Fisheries have been shown to be directly related to optimal physiological tolerances, particularly temperature. Therefore the authors sought to examine the range boundaries and centroids of commercial fisheries over time, and therefore developed the mean temperature catch index to track response to temperature over time.

The MTC was calculated as the average temperature preference of species by their annual catch from 1970 to 2006. The data were further classified by fifty-two large marine ecosystems, LMEs qualified as temperate, subtropical, and tropical. Overall it was found that mean temperature catch increased by a rate of 0.19°C per year, with the largest increases in the northeast Pacific Ocean and northeast Atlantic Ocean. It was also found that there was a close relationship between the rate of SST and MTC changes, suggesting it is a valid proxy for range shifts in relation to climate change.

The relationship between MTC and SST change was undermined by an overall lack of data, as well as increased fishing efforts since the 1970s confounding data irregularities. Nonetheless, the results suggest increased catch rates of warmer water species at higher latitudes and decreases in tropical fisheries. These adaptations to climate change could have important implications on fisheries management and global food security, as many tropical nations are dependent on fisheries for nutritional and economic value.

Cheung, W, Watson, R and Pauly, D. 2013. Signature of Ocean Warming in Global Fisheries Catch. Nature, 497, 365-369 doi: 10/1038/nature12156

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