Climate Variability, Fish, and Fisheries

Abstract

Fish population variability and fisheries activities are closely linked to weather and climate dynamics. While weather at sea directly affects fishing, environmental variability determines the distribution, migration, and abundance of fish. Fishery science grew up during the last century by integrating knowledge from oceanography, fish biology, marine ecology, and fish population dynamics, largely focused on the great Northern Hemisphere fisheries. During this period, understanding and explaining interannual fish recruitment variability became a major focus for fisheries oceanographers. Yet, the close link between climate and fisheries is best illustrated by the effect of “unexpected” events—that is, nonseasonal, and sometimes catastrophic—on fish exploitation, such as those associated with the El Niño–Southern Oscillation (ENSO). The observation that fish populations fluctuate at decadal time scales and show patterns of synchrony while being geographically separated drew attention to oceanographic processes driven by low-frequency signals, as reflected by indices tracking large-scale climate patterns such as the Pacific decadal oscillation (PDO) and the North Atlantic Oscillation (NAO). This low-frequency variability was first observed in catch fluctuations of small pelagic fish (anchovies and sardines), but similar effects soon emerged for larger fish such as salmon, various groundfish species, and some tuna species. Today, the availability of long time series of observations combined with major scientific advances in sampling and modeling the oceans’ ecosystems allows fisheries science to investigate processes generating variability in abundance, distribution, and dynamics of fish species at daily, decadal, and even centennial scales. These studies are central to the research program of Global Ocean Ecosystems Dynamics (GLOBEC). This review presents examples of relationships between climate variability and fisheries at these different time scales for species covering various marine ecosystems ranging from equatorial to subarctic regions. Some of the known mechanisms linking climate variability and exploited fish populations are described, as well as some leading hypotheses, and their implications for their management and for the modeling of their dynamics. It is concluded with recommendations for collaborative work between climatologists, oceanographers, and fisheries scientists to resolve some of the outstanding problems in the development of sustainable fisheries.

Effects of climate variability and climate change on the fishing conditions for grey mullet (Mugil cephalus L.) in the Taiwan Strait

“…Black bar: fishing effort of purse seiners; Grey bar: fishing effort of gill nets; Red line: CPUE of purse seiners; Blue bar: CPUE of gill nets Second, increasing sea surface temperatures (SSTs) and other climatic effects associated with global warming have contributed to reduce catches of grey mullet in Taiwan (Hung and Shaw 2006). Climatic effects on the fluctuations of fish populations and fisheries have long been recognized and continue to be critical (Lehodey et al 2006;Hsieh et al 2009;Tzeng et al 2012a;Lan et al 2012). The most widely studied climatic events causing impacts on fishes include those on an inter-annual scale, such as the El Niño/Southern Oscillation (ENSO) (Lehodey et al 2006;Hsieh et al 2009), and on a decadal scale, such as the Pacific Decadal Oscillation (PDO) (Mantua et al 1997;Tzeng et al 2012a).…”

“…Climatic effects on the fluctuations of fish populations and fisheries have long been recognized and continue to be critical (Lehodey et al 2006;Hsieh et al 2009;Tzeng et al 2012a;Lan et al 2012). The most widely studied climatic events causing impacts on fishes include those on an inter-annual scale, such as the El Niño/Southern Oscillation (ENSO) (Lehodey et al 2006;Hsieh et al 2009), and on a decadal scale, such as the Pacific Decadal Oscillation (PDO) (Mantua et al 1997;Tzeng et al 2012a). In particular, large-scale climatic oscillations such as the ENSO can cause SST changes on an inter-annual scale (Tzeng et al 2012b;Kuo and Lee 2013).…”

Centennial-scale fluctuations and regional complexity characterize Pacific salmon population dynamics over the past five centuries

“…For example, anomalously high returns of adult salmon to Kukaklek Lake in the past decade, unprecedented since record keeping began in 1956, appear to have been part of a natural cycle in sockeye productivity for that lake (7). In the absence of harvesting, climate is often considered to be the main driver of large shifts in fish abundance (2). Indeed, interdecadal variability in North Pacific sockeye salmon production during the past century has been tied to marine ecosystem shifts linked to the PDO (12,27).…”

“…Oncorhynchus nerka | nitrogen stable isotopes | fisheries | paleolimnology L arge fluctuations in abundance are a hallmark of fish stocks (1,2); fish abundance can fluctuate substantially over interannual to centennial time scales (3)(4)(5). Recent short-term variation in stock abundance can be characterized by fisheries catch records and scientific survey data, but to characterize low-frequency variability requires novel ecological approaches (6).…”

“…Low-frequency variation in fish abundance is often attributed to climatic forcing (2,9) or harvesting (10,11). At a broad scale, persistent multidecadal shifts in North Pacific salmon production throughout the 20th century have been linked to the Pacific Decadal Oscillation (PDO), with total salmon production in Alaska high when the PDO is in a warm phase and vice versa for cold phases (12).…”