Evaluating Nursery Habitat Quality for Juvenile Rock Sole (Lepidopsetta polyxystra) Using Lipid Class Condition Indices, Fatty Acid Trophic Markers and Otolith Microstructural Analyses

Northern rock sole, Lepidopsetta polyxystra, from nurseries in Kodiak Island, Alaska have demonstrated significant inter-annual variability both in their depth distribution and abundance. Much of this variation has been correlated with the density of polychaete tubes; principally Sabellides sibirica existing on nursery grounds. However, the mechanistic importance of worm tubes to flatfish is unknown but could be either an alternative refuge and/or a feeding habitat. We used lipid condition factors and fatty acids to explore the trophic role of polycheate production in driving observed variation in juvenile flatfish energetics at two nursery habitats in 2009 and 2010. Lipid condition indices were higher in 2010 fish than in 2009. This elevation in 2010 was associated with lower fish densities, earlier timing of metamorphosis and higher growth following metamorphosis. Fatty acid biomarkers exposed differences in trophic structure between nursery embayments that were consistent across years. Higher condition in rock sole at Holiday Beach was associated with elevated diatom markers in the food web. Multivariate analyses of fatty acids indicate that juvenile rock sole display a close trophic association with polycheate worms.