MEPS 438:229-239 (2011)  -  DOI: https://doi.org/10.3354/meps09316

ABSTRACT: Multiple lines of evidence suggest that changes in the marine climate in the eastern Bering Sea are leading to numerical and distributional shifts in fish populations that may affect the balance of predator−prey relationships. A rapidly increasing arrowtooth flounder Atheresthes stomias population has prompted concern about the growing threat of arrowtooth flounder predation on economically valuable walleye pollock Theragra chalcogramma. The goal of this study was to investigate the overall increasing trend of arrowtooth flounder at a finer spatial resolution to better understand the potential spatial variability in their predatory impact under a changing climate. The specific objectives were to determine whether arrowtooth flounder were increasing equally throughout the eastern Bering Sea and, if not, (1) identify areas with dissimilar abundance trends and (2) explore physical and biological habitat characteristics that may be contributing to these differences. Clustering arrowtooth survey catch per unit effort revealed 4 distinct spatial groups showing stable, increasing, and variable trends. Increasing bottom water temperature and depth were associated with higher proportions of trawls containing arrowtooth and higher catch rates. Age-1 and -2 pollock were the predominant prey in all areas, but higher rates of non-empty stomachs in the northwest region indicated that current predatory impacts on pollock may be higher there. Favorable physical habitat (deep and warm) and diet trends (full stomachs) suggest that arrowtooth flounder in the northwest region of the eastern Bering Sea have the potential to increase further, perhaps to the abundance levels seen in the high-density area where they may have reached carrying capacity.

KEY WORDS: Arrowtooth flounder · Atheresthes stomias · Bering Sea · Fish distribution · Cluster analysis · Predation · Walleye pollock · Climate change