European flounder foraging movements in an estuarine nursery seascape inferred from otolith microchemistry and stable isotopes

Despite the importance of estuarine nurseries in the regulation of many fish stocks, temporal and spatial movements and habitat use patterns of juvenile fish remain poorly understood. Overall, combining several movement metrics allowed us to characterize dispersal patterns of juvenile flounder, Platichthys flesus, along an estuarine seascape. Specifically, we investigated otolith microchemistry signatures (Sr:Ca and Ba:Ca ratios) and stable isotope ratios (delta 13C and delta 15N) in muscles of these juveniles, during three consecutive years to assess inter -annual fluctuations in their home range and isotopic niches. The morphological condition and lipid content of individuals were lower in years of high as compared to low dispersal along the estuarine gradient. We discuss these results in relation to the ecosystem productivity and intra-and inter-specific competition level, which in turn affects movements and foraging behaviors of juvenile flounders.

Automated summary

This study characterized the dispersal patterns and inter-annual fluctuations of home range and isotopic niches in juvenile flounder using otolith microchemistry signatures and stable isotope ratios. The results showed that individuals had lower morphological condition and lipid content in high dispersal years along the estuarine gradient. These findings provide insights into the effects of ecosystem productivity and intra-and inter-specific competition on the movements and foraging behaviors of juvenile flounders.