Trophic plasticity of larval notothenioid fish Harpagifer antarcticus in shallow waters from the South Shetland Islands, Antarctica

Adaptive plasticity in foraging of early life stages of marine fishes is highly relevant, particularly in environments such as the Antarctic inshore waters. In this study we analyzed the trophic habits, feeding success and selectivity of larval spiny plunderfish Harpagiferantarcticus (Osteichthyes: Harpagiferidae) collected weekly in austral summer 2014 and 2015 at Bahía Chile, Greenwich Island, South Shetland Islands. Based on the stomach contents of 202 individuals ranging between 5.97 and 10.66 mm, the spiny plunderfish was omnivorous, with chain-forming diatom Thalassiosiraminuscula, euphausiid eggs and copepodites as the main prey items. The feeding success, measured as prey number per gut and total volume per gut, and the trophic niche breadth were independent of the standard length. Only the maximum prey size (width) was positively correlated with larval size, suggesting a preference for larger prey as larvae grow. At the interannual scale, significant differences were only detected in the ingested prey per gut, with higher values during summer 2014. In this season, trophic niche breadth increased with larval size. At the weekly scale, and after storm winds from southeast and high turbulence in surface waters, H. antarcticus larvae switched their selective feeding based on large prey (i.e., copepodites) to a more opportunistic feeding strategy, relying on large abundance of small (i.e., T. minuscula) to medium-size prey (euphausiid eggs). The present results suggest that larval spiny plunderfish exhibit feeding behavior plasticity, ensuring higher feeding rates after major changes triggered by meteorological conditions in a shallow embayment of the South Shetland Islands.