The food and feeding relationships of larval and 0+ year juvenile fishes in lowland rivers and connected waterbodies. I. Ontogenetic shifts and interspecific diet similarity.

Many fish species are zooplanktivorous at the onset of exogenous feeding, but distinct shifts in their foraging biology may occur with development. This study investigated the food and feeding relationships of the larvae and 0+ year juveniles of 13 fish species in ‘main river’, ‘marina’ and ‘pond’ macrohabitats in the lower River Trent, England. Young larvae had narrow diet spectra, with feeding diversity and the importance of species-specific traits increasing with development. Two main ontogenetic shifts in diet were differentiated, corresponding with the transition from finfold to finformed larvae, and from the larval to the juvenile period. Dietary overlap was generally greatest among ecologically similar species, with competition and resource partitioning most likely where prey availability was lowest. The greater availability of zooplankton in connected waterbodies compared with main river channels provides suitable prey for a wide range of fish species, and may enhance recruitment success. [ABSTRACT FROM AUTHOR]