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If you catch only the final scene of your favorite show, you see how things end up; you know who captures the throne. But you can only guess how they got there. You missed the swordfight, the betrayal, the final power play. “The most exciting thing about this research is to try to understand the forces that motivate ecosystem change while it is in progress,” says NOAA Fisheries biologist Dr. Janet Duffy-Anderson, who initiated the study in collaboration with Ed Farley (NOAA Fisheries), Ron Heintz (NOAA Fisheries), and Phyllis Stabeno (NOAA’s Pacific Marine Environmental Laboratory). She wants to watch the whole episode.
A Change of Regimes
If cold conditions returned in 2015, the changes might go no further than that. It takes more than one year to transform the ecosystem. It is during a series of warm years—a warm regime—that far-reaching changes are set in motion. And 2015 was predicted to be the second year of a prolonged warm phase. Duffy-Anderson and colleagues recognized this chance to see what really happens during a change of regimes in the Bering Sea. The team acted quickly to plan a special cruise on the NOAA Ship Oscar Dyson. And their efforts were rewarded: 2015 has been a very warm year. “After this cruise we will have the data in hand to intensively study this Bering Sea ecosystem shift,” says Duffy-Anderson. “This is a win for science.” A Pivotal Role Pollock plays a central role in the Bering Sea ecosystem. Nearly all of the food energy that travels up the food web from plankton to predators gets there via pollock: pollock eat plankton and small fish; predatory fish, seabirds, and marine mammals eat pollock. If a predator doesn’t eat pollock, chances are it eats something that ate pollock. Humans are major pollock predators too. If you have lunched on fish sticks or a California roll, you have probably eaten pollock. Bering Sea pollock supports the largest commercial fishery in the U.S and the second largest in the world. Besides supplying an important food resource to many consumers, the fishery provides a livelihood for the many people who catch, package, and distribute pollock. Drama Plot Twists At first glance, Bering Sea pollock seem to do best in warm conditions. During a single warm year, young pollock thrive. But if warm conditions persist for more than a year, the population declines. In the long run, pollock do better during a cold regime. Here’s what scientists think happens. Warm phases feature an abundance of small, low-fat copepods; in cold conditions, larger, oil-rich copepods take the stage. After a warm summer on a low-fat diet, young pollock are abundant and lean; their cold-summer counterparts end up fewer but fatter. Then winter comes, and in winter, fatter is fitter. Pollock with bigger energy stores seem to survive better. Based on data collected during cold years, this hypothesis holds true. No one has had a chance to test it during a warm regime – until now. Cast and Crew A multidisciplinary team of experts from NOAA Fisheries, the University of Alaska, and NOAA’s Pacific Marine Environmental Laboratory will work together to weave these subplots into a complete story. Duffy-Anderson hopes this cruise will answer some big questions: How long does it take for the ecosystem to change? Why is there a lag between a shift in climate and a swing in pollock populations? When does the copepod community change enough to affect pollock nutrition? Understanding how ecosystem change unfolds—the whole episode-- will be an important contribution to NOAA Fisheries’ continuing effort to understand and predict how a changing climate will affect Alaska’s ecosystem and fisheries, and the people who depend on them. Stay tuned for live reports from the Bering Sea cruise this September on the AFSC Blog More information on the Bering Sea ecosystem and climate Duffy-Anderson, J.T., Barbeaux, S., Farley, E., Heintz, R., Horne, J., Parker-Stetter, S., Petrik, C., Siddon, E., and Smart, T. 2015. A critical synthesis of the first year of life of walleye pollock (Gadus chalcogrammus) in the eastern Bering Sea and comments on implications for recruitment. Deep Sea Research II: Topics in Oceanography, in press. DOI: 10.1016/j.dsr2.2015.02.001 Siddon, E.C., Kristiansen, T., Mueter, F.J., Holsman, K.K., Heintz, R.A., and Farley, E.V. 2013. Spatial Match-Mismatch between Juvenile Fish and Prey Provides a Mechanism for Recruitment Variability across Contrasting Climate Conditions in the Eastern Bering Sea. PLOS One. DOI: 10.1371/journal.pone.0084526 Stabeno, P.J., N.B. Kachel, S.E. Moore, J.M. Napp, M. Sigler, A. Yamaguchi, and A.N. Zerbini. 2012. Comparison of warm and cold years on the southeastern Bering Sea shelf and some implications for the ecosystem. Deep-Sea Research Part II 65–70:31–45, http://dx.doi.org/10.1016/j.dsr2.2012.02.020.
For more information please contact Marjorie Mooney-Seus,
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