Using Prey Life-History to Infer Temporal and Spatial Shifts in Foraging Behavior of Juvenile Flatfish from an Alaskan Nursery Habitat

Diets of two juvenile Plueronectidae species were examined from Port Moller, Alaska during August of 2012. Stomach contents were examined from 263 age-0 Northern Rock Sole (Lepidopsetta polyxystra) and 168 age-1 Yellowfin Sole (Limanda aspera). Prey items in diets were binned into four location and behavior strategies: endobenthic, epibenthic, hyperbenthic, and planktonic. Prey bins were selected to span potential patterns of association with the substrata, ranging from close association with the sediment (endobenthic) to no association with the sediment (planktonic) during active foraging.  These categories provide proxy information on juvenile fish foraging strategy, as close association with the sediment is linked to risk-averse behavior is flatfishes.  We determined that Northern Rock Sole and Yellowfin Sole have significantly different foraging behaviors based on analyses of the prey bins. Feeding intensity was highest in Northern Rock Sole after sunset and on more pelagic prey while Yellowfin Sole shows no diurnal patterns in feeding intensity. We hypothesize that Northern rock sole juveniles are risk-averse, but engage in intensive crepuscular feeding to mitigate exposure as they engage in prey capture of euphausiids in the hyperbenthos, while Yellowfin Sole juveniles demonstrate less tolerance for risk remaining close to the sediment throughout the day.