The separation of the effects of environmental variability from the impacts of fishing has been elusive, but is essential for sound fisheries management1,2,3,4,5,6,7. We distinguish environmental effects from fishing effects by comparing the temporal variability of exploited versus unexploited fish stocks living in the same environments. Using the unique suite of 50-year-long larval fish surveys from the California Cooperative Oceanic Fisheries Investigations4 we analyse fishing as a treatment effect in a long-term ecological experiment. Here we present evidence from the marine environment that exploited species exhibit higher temporal variability in abundance than unexploited species. This remains true after accounting for life-history effects, abundance, ecological traits and phylogeny. The increased variability of exploited populations is probably caused by fishery-induced truncation of the age structure, which reduces the capacity of populations to buffer environmental events1,5,8,9. Therefore, to avoid collapse, fisheries must be managed not only to sustain the total viable biomass but also to prevent the significant truncation of age structure1,5,8,9. The double jeopardy of fishing to potentially deplete stock sizes and, more immediately, to amplify the peaks and valleys of population variability7, calls for a precautionary management approach10,11.
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We thank the CalCOFI for the use of the data. R. Hewitt, D. Checkley, M. Ohman, S. Sandin, M. Maunder, P. Hastings, K. Roy, D. Lucas and S. Glaser provided discussion and comments on this work. A. MacCall, K. Hill, D. Sampson, I. Stewart, J. Cope, D. Aseltin-Nelson and J. Mason provided fisheries-related data. B. Macewicz, N. Lo, B. Watson and S. Suyama provided data and comments on life-history traits of fishes. Our study was funded by NOAA Fisheries and the Environment (FATE), the National Marine Fisheries Service, NSF/LTER CCE ‘Nonlinear Transitions in the California Current Coastal Pelagic Ecosystem’, the Center for Marine Bioscience and Biotechnology, National Taiwan Oceanic University, the Deutsche Bank Complexity Studies Fund and the Sugihara Family Trust. Author Contributions C.H. and G.S. conceived the original study. C.H. is responsible for the statistical analyses and uncovering the main result. All co-authors contributed to refining the analysis, framing and interpreting the result, and to its final exposition.
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About this article
Acta Oceanologica Sinica (2018)