Data sets of primary production and productivity have occurred only intermittently over the past 30 years. These data are still being located, collated and summarized, and analyses is beginning. Some work that is farther along is a comparison of satellite-derived productivity and production data with environmental factors for the past five years by L.J. Miller and Dave Eslinger of the University of Alaska Fairbanks. L.J. Miller's master's thesis of this analysis should be available shortly. Data are from benthic trawl surveys covering the eastern and central Bering Sea shelf since 1972 and each species contains 7,426 stations sampled during that time period.
Analyses are underway including comparison with environmental data.
A second hypothesis that is not so well tested out yet is that oceanographic conditions, particularly temperatures, limit the growth of some populations. In cold years with an extensive cold pool, pollock recruitment is reduced because of lower egg hatch, and higher concentrations of adult pollock result in increased cannibalism. In warm years with a small cold pool, pollock recruitment is enhanced because of higher egg hatch, and the dispersal of pollock results in decreased cannibalism. Within a year or so, the population catches up so that cannibalism balances egg hatch. This may have been the mechanism that caused the pollock fluctuations over the regime shift.