Functional foraging habits and dietary overlap of yellowfin sole (Limanda aspera) and northern rock sole (Lepidopsetta polyxystra) in a coastal nursery of the Bering Sea

Understanding patterns of foraging and competition in nursery habitats can elucidate patterns of productivity in multispecies fisheries. Yellowfin sole (Limanda aspera) and northern rock sole (Lepidopsetta polyxystra) co-occur throughout the Bering Sea where they support major fisheries. We examined the diets and foraging ecology of juvenile yellowfin sole and northern rock sole (35-100 mm in standard length) captured along the north side of the Alaska Peninsula and in the Port Moller-Herendeen Bay system, the largest marine embayment in the southeastern Bering Sea. As observed in other parts of their ranges, the diets of both species included polychaetes and amphipods. The primary difference in the diets of these species was that the prey of yellowfin sole were almost exclusively endobenthic and epibenthic invertebrates (>82.7% by weight combined) and the northern rock sole consumed substantial amounts of hyperbenthic mysids and pelagic euphausiids (42% combined). Overall dietary overlap was low (Schoener index [SI]=0.39), in part due to differences in microhabitat use. At sampling stations where both species co-occurred, dietary overlap was notably higher (SI=0.55). Patterns of functional foraging habits and juvenile niche separation that facilitate coexistence of these species throughout their range were expressed with a novel application of principal components analysis of the abiotic (habitat characteristics) and biotic (consumer traits) factors associated with commonly occurring prey types.