FY 1995

An exploratory analysis of associations between biotic and abiotic factors and year class strength of Gulf of Alaska walleye pollock

Megrey, B.A., S.J. Bograd, W.C. Rugen, A.B. Hollowed, P.J. Stabeno, S.A. Macklin, J.D. Schumacher, and W.J. Ingraham, Jr.

In Climate Change and Northern Fish Populations, R.J. Beamish (ed.), Can. Spec. Publ. Fish. Aquat. Sci., 121, 227–243 (1995)

This analysis examines the relative importance of various physical and biological factors on year-class strength of walleye pollock (Theragra chalcogramma) in Shelikof Strait, Alaska. Biological data for the analysis consists of a recruitment time series covering the period 1962-89 and egg and larval abundance time series for 1981-89. Physical data describe atmospheric and oceanic features of the region including estimates of precipitation, turbulent wind mixing, volume transport, and sea-surface temperature. Principal component analysis showed that 37% of the variance in the physical data was captured by the first two modes. The second mode, attributed to large-scale atmospheric circulation, separated conditions that contribute to high and low recruitment. Univariate and multivariate statistical techniques suggested that age-0 and age-1 abundance estimates as well as age-2 recruitment estimates are related to precipitation, an index of atmospheric sea-level pressure gradient, and local wind mixing. From the results of these analyses, several hypotheses are proposed: spring wind mixing in Shelikof Strait affects larval survival; large-scale atmospheric circulation affects processes leading to recruitment; baroclinicity may generate mechanisms conducive to larval survival; and effects of the physical environment on predation and behaviour may affect juvenile survival.