Water temperatures in the southeastern Bering Sea influence the density of walleye pollock Theragra chalcogramma early life stages, potentially influencing spatial distributions and the phenology of reproduction and development. We quantified stage-specific changes in spatial and temporal distributions under cold-and warm-water conditions using generalized additive models. Analyses showed that walleye pollock egg and yolksac larval spatial distributions are unaffected by temperature, suggesting that spawning locations are stable. Preflexion larvae, late larvae, and juveniles shift onto the shelf under warm conditions, similar to spatial shifts observed in distributions of sub-adults and adults. Temporal distributions were used to address the hypothesis that timing of the density peak at each stage is delayed under cold conditions. Differences in the timing of density peaks supported the hypothesis that the timing of spawning, hatching, larval development, and juvenile transition are temperature-dependent. The current analysis represents the best support available for the importance of temperature to walleye pollock in determining early life stage development and population trends in the eastern Bering Sea. Our data indicate that future changes in water temperatures could influence the early life stages of an ecologically dominant member of the Bering Sea community by changing phenology and habitat use in the first several months of life.KEY WORDS: Theragra chalcogramma · Temperature · Distribution · Phenology · Bering Sea
Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 455: [257][258][259][260][261][262][263][264][265][266][267] 2012 temperature during the pollock post-spawning feeding season (Kotwicki et al. 2005). Biomass increased with summer temperatures and the feeding migration progressed farther north and inshore (east) from spawning grounds as temperature increased. Kotwicki et al. (2005) hypothesized that warmer water temperatures advance the post-spawning feeding migration by advancing the timing of spawning. They did not address the alternate hypothesis that spawning distribution changes in response to temperature conditions.Colder than average years are characterized by late sea-ice retreat from the shelf in the spring, water column temperatures < 2°C over the shelf during spring and summer, and abundant large-bodied zooplankton . Warmer than average years are characterized by early ice retreat, continental shelf water temperatures > 2°C during spring and summer, and smallbodied zooplankton. Sea-ice conditions also determine the extent and location of a pool of cold bottom water in the summer over the middle shelf (50 to 100 m depth, Stabeno et al. 2012a). Pollock distributions generally are restricted to areas > 2°C, such as those found outside the cold pool (Wyllie-Echeverria & Wooster 1998). Therefore, in warm years, a larger area of thermally-suitable habitat is available to pollock over the continental shelf, particularly over the midd...