Marine resources and fisheries are coupled social-ecological systems that make substantial contributions toward food, livelihoods and foreign trade for many countries. While fisheries are often managed as independent populations, human and ecosystem processes link fisheries together in complex networks. Synchronous fluctuations among fisheries amplify variation and can destabilize ecosystems and economies, but the strength of synchrony remains unclear. We used wavelet coherence, a novel approach that accounts for multiple timescales and time lags. Furthermore, recent developments in the computation of wavelet coherence have enabled significance testing to be performed using fourier surrogates that retain temporal autocorrelation properties, a common feature in ecological time-series data. Here, we analyzed 1092 marine fisheries catch time-series representing 510 unique species from 15 different regions to test for the presence of coherence at global and regional scales. These time-series consisted of annual catches over the years 1955-2014, more than 60 years of data.
Results/Conclusions
We found five times as many pairs of coherent fisheries as expected from a null model and nearly every fishery (96%) was coherent with at least one other fishery globally. Coherent pairs of fishery catches were clustered within regions. Coherence was strongest in the northeast Atlantic, western central Pacific, and eastern Indian Ocean and among large pelagic species (tunas and billfishes). Most of these relationships were synchronous with no time lags, which implied external factors such as fishing behavior and climate. Regions with higher synchrony had lower stability in aggregate fishery catches, which can have negative consequences for food security and economic wealth of the fishing communities and countries located within these regions.