Ontogenetic Diet Shifts in Early Life History Stage Estuarine Fishes (Family Sciaenidae) from the Chesapeake Bay

Early life history stage (ELHS) fishes are more susceptible to starvation than adults and successful feeding at these stages is critical. Members of the family Sciaenidae are an excellent model group to investigate ontogenetic diet shifts because as adults they occupy a broad spectrum of feeding niches. Stomachs have been excised from 376 specimens from 11 species of sciaenids representing two foraging guilds (benthic sciaenids vs. pelagic sciaenids) collected from the Chesapeake Bay. Stomach contents were identified to the lowest possible taxonomic level and then pooled into the prey’s primary habitat (i.e., pelagic shrimp, benthic shrimp). To examine ontogenetic shifts in sciaenids, mean percent number of each prey category was calculated to reduce the bias associated with small sample sizes. Dietary shifts were observed in larval sciaenids by 28 mm standard length (SL); 1/3 of the benthic foraging sciaenid diet consisted of benthic crustaceans whereas pelagic sciaenids were consuming mostly pelagic crustaceans (47%). Before 28 mm SL, both benthic and pelagic foraging sciaenids were consuming pelagic crustaceans, mostly copepods. Many of the examined sciaenid species have overlapping spawning and ingress periods, therefore, the ability to partition foraging habitats in ELHS may be a mechanism to reduce competition.