The fate of first-year pollock in fall and winter depends on availability of large crustacean plankton

LifeLinkedtoIce First year pollock


Box 6. Earlier sea ice melt may lead to a decline in the Bering Sea pollock fishery

The walleye pollock fishery is a commercial fishery in the northwestern Pacific Ocean, with landings of 1.3 million tonnes in 2011 [210] valued at 375 million US dollars. Until recently the prevailing view was that climate warming would lead to greater pollock production, but this has been shown not to be the case

[211, 212].
Conditions in the Bering Sea shift between warm and cool phases, driven by the broad-scale climate pattern of the Pacific Decadal Oscillation [213]. In warm years, the sea ice melts early in the year and the sea becomes well mixed by winter storms that are still prevalent. Instead of following the general pattern of earlier melt leading to earlier algal blooms [214], the wind mixing keeps the surface waters from warming up and delays the annual algal bloom. In cold years, ice breaks up later and algal blooms develop quickly in the stable layer of meltwater that forms on the surface of the sea [212].
The net result is that in years with earlier ice melt the delayed algal blooms lead to a reduced crop of the large crustacean zooplankton that are the best food for pollock in their first summer. The young pollock do not build up the energy reserves they need to survive the winter and they are more vulnerable to predation and to cannibalism by larger pollock. The following spring, there are few year-old pollock entering the population [212]. High sea-surface temperatures in late summer also reduce the availability of large crustaceans for the young pollock [211].
Poor survival of first-year fish during the warm years with early sea ice melt from 2002 to 2005 led to a severe decline in Bering Sea pollock. Stocks rebounded in the colder years that followed [193]. A Bering Sea climate regime with more prolonged warm periods, as is projected by climate models, will likely lead to a decline in stocks and a reduced walleye pollock fishery [211].



Figure 26. The fate of first-year pollock in fall and winter depends on availability of large crustacean plankton

Predation, cannibalism by larger pollock, and starvation in winter increase for first-year pollock in years with earlier sea ice melt (top diagram).

From Hunt et al. 2011 [212]



Conservation of Arctic Flora and Fauna (CAFF) 

The data can be downloaded freely. Users are requested to reference the source.

Eamer, J., Donaldson, G.M., Gaston, A.J., Kosobokova, K.N., Lárusson, K.F., Melnikov, I.A., Reist, J.D., Richardson, E., Staples, L., von Quillfeldt, C.H. 2013. Life Linked to Ice: A guide to sea-ice-associated biodiversity in this time of rapid change. CAFF Assessment Series No. 10. Conservation of Arctic Flora and Fauna, Iceland. ISBN: 978-9935-431-25-7.



210. NOAA. 2012. Fisheries of the Unitied States 2011. Current Fishery Statistics No. 2011. National Marine Fisheries Service, Office of Science and Technology, National Oceanic and Atmospheric Administration, Silver Spring, MD.
211. Mueter, F.J., Bond, N.A., Ianelli, J.N., and Hollowed, A.B. 2011. Expected declines in recruitment of walleye pollock (Theragra chalcogramma) in the eastern Bering Sea under future climate change. Ices Journal of Marine Science 68(6): 1284-1296.doi:10.1093/icesjms/fsr022.
212. Hunt, G.L., Coyle, K.O., Eisner, L.B., Farley, E.V., Heintz, R.A., Mueter, F., Napp, J.M., Overland, J.E., Ressler, P.H., Salo, S., and Stabeno, P.J. 2011. Climate impacts on eastern Bering Sea foodwebs: a synthesis of new data and an assessment of the Oscillating Control Hypothesis. ICES Journal of Marine Science: Journal du Conseil 68(6): 1230-1243. doi:10.1093/icesjms/fsr036.
213. Zhang, J.L., Woodgate, R., and Moritz, R. 2010. Sea ice response to atmospheric and oceanic forcing in the Bering Sea. Journal of Physical Oceanography 40(8): 1729-1747. doi:10.1175/2010jpo4323.1.


214. Kahru, M., Brotas, V., Manzano-Sarabia, M., and Mitchell, B.G. 2011. Are phytoplankton blooms occurring earlier in the Arctic? Global Change Biology 17(4): 1733-1739. doi:10.1111/j.1365-2486.2010.02312.x.



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