| The naked goby, Gobiosoma bosci, is an abundant small bodied benthic fish found in estuaries along the east coast of the United States. In the present study, naked gobies were collected from four states along the western Atlantic (South Carolina, North Carolina, Maryland, and New Jersey) to investigate diet and feeding ecology. Gut content analysis revealed that naked gobies are benthic microcarnivores that feed primarily on harpacticoid copepods, amphipods, and polychaetes. As generalist, opportunistic predators, diet composition varied slightly with geographic region, habitat and season, but major prey taxa were consumed at all localities. By quantifying gut fullness and dietary niche width, the data strongly support the proposition that naked gobies are daytime visual predators, that reproductive behavior may suppress foraging activity, and dietary niche width broadens with an increase in the diversity of prey items available. An ontogenetic meiofaunal to macrofaunal diet shift was documented, and the behavioral targeting or retention of meiofaunal prey items decreases gradually with ontogeny. The volumetric contribution of macrofaunal prey items is very high even at small predator body sizes (12 mm standard length, SL), suggesting a rapid ontogenetic shift towards the energetic importance of macrofauna. The volumetric diet shift can be described by two regions: a region of low variability (fixed feeding patterns) in gobies > 20 mm SL, and a region of high variability (plastic feeding patterns) in gobies < 20 mm SL. The observed diet shift may be regulated by ontogenetic changes in metabolism, and potential changes in the energetic contributions of meiofauna vs. macrofauna throughout ontogeny. A simple framework to quantitatively describe diet shifts using data collected from gut content analysis is proposed and explained. These results contribute to our understanding of the life history of the naked goby, and the ecological role they play in estuaries along the Atlantic coast of the US. |
