Early life history ecology for five commercially and ecologically important fish species in the eastern and western Gulf of Alaska

Abstract

The Gulf of Alaska Integrated Ecosystem Research Program is a multi-disciplinary study examining interactions between physical and biological oceanography to understand how the environment influences the survival and recruitment of early life stages of select commercially and ecologically important groundfish species. Biological and oceanographic surveys in the eastern and western Gulf of Alaska were conducted during spring and summer of 2011 and 2013; we present a synthesis of ichthyoplankton data. The results describe seasonal (spring vs. summer), regional (eastern vs. western Gulf of Alaska), and interannual (2011 vs. 2013) variation in distribution, abundance, and larval sizes of the focal species. In spring, Pacific Cod (Gadus macrocephalus) larvae were more abundant in 2013 than 2011 and occurred primarily in the western Gulf of Alaska near Kodiak Island, over the shelf, and over the continental slope. Walleye Pollock (Gadus chalcogrammus) larvae were also more abundant in the western Gulf of Alaska, with substantially higher abundance in 2013. Larval rockfish (predominantly Pacific Ocean Perch; Sebastes alutus) were collected in deep water or were associated with the slope, troughs and canyons intersecting the slope, and the outer shelf. Rockfish larvae were collected throughout the study region in spring, with no significant differences in abundance between regions or years. In summer, rockfish (predominantly species other than Pacific Ocean Perch) were more widely distributed over the shelf and were more abundant in the eastern Gulf of Alaska both within and across years, indicating species-specific spawning events. Sablefish (Anoplopoma fimbria) larvae, however, were more abundant in the eastern Gulf of Alaska and in 2011 and were predominantly collected near areas of deep water such as Yakutat Canyon. In 2011, Arrowtooth Flounder (Atheresthes stomias) abundances of larvae were higher in the western Gulf of Alaska, whereas in 2013 abundances were higher in the eastern Gulf of Alaska. Arrowtooth Flounder larvae were collected primarily along the slope and near canyons and troughs. The results from individual years presented here can be used in individual-based model validation of connectivity matrices, delineating transport patterns to suitable nursery habitat, and evaluating recruitment bottlenecks for these focal species in the Gulf of Alaska. Future research will examine patterns of community structure and assemblage diversity using the comprehensive ichthyoplankton dataset. The observed ecological patterns provide insight into how environmental forcing may influence early life history aspects of recruitment.