Patterns of Larval Source Distribution and Mixing in Early Life Stages of Pacific Cod (Gadus macrocephalus) in the Southeastern Bering Sea

Pacific cod (Gadus macrocephalus) in the southeastern Bering Sea aggregate at discrete spawning locations but there is little information on patterns of larval dispersal and the relative contribution of specific spawning areas. Age-0 Pacific cod from two cohorts were examined to determine: if size, age, and otolith chemistry vary among capture locations; if variation in early larval otolith elemental signatures can be used to infer the number of chemically distinct sources contributing to juvenile recruits; and to what extent juvenile collection locations are represented by fish with similar chemical histories? Five chemically distinct groups of larvae were identified in the 2006 cohort and three groups in 2008; however, three groups accounted for 80-100% of the juveniles in each year. There were non-random spatial distributions of early stage larvae in both years, which reflected interannual variation in regional oceanography. There was also coherence in chemical signatures within groups of fish throughout the early life history. The variation in elemental signatures throughout the early life history indicates that otolith chemical analysis could be an effective tool to further clarify larval sources and dispersal and estimate the contributions of juvenile nursery habitats to the adult population within the southeastern Bering Sea.