California Sea Grant College Program

Studies of fish diets can improve the understanding of trophic distributions

and the predatory role of a species in an ecosystem. Identifying the spatial and

temporal variability in the diets of fishes can provide useful information for stock

assessments and management. Yellowtail Rockfish (Sebastes flavidus) are a

commercially and recreationally important fishery species, and abundant along

the central California coast, yet the most recent studies of diets occurred over 20

years ago in Oregon and Washington. To provide current information from

California, I examined the food habits of Yellowtail Rockfish collected near

Cordell Bank, the Farallon Islands, and Half Moon Bay in 2013 and 2014 using

gut content and stable isotope analyses. Yellowtail Rockfish analyzed in this

study were semi-pelagic predators, feeding primarily on tunicates, crustaceans,

and teleosts. Based on δ15N values, fish caught in 2013, on average, were

feeding at lower trophic levels than those caught in 2014, and δ13C values

indicated that fish caught at the northern-most sites were feeding on more

pelagic-influenced carbon sources. Yellowtail Rockfish in central California can

be described as opportunistic feeders because predation patterns were

temporally localized, and diets consisted mostly of transitory prey sources. The

Yellowtail Rockfish diet information presented in this study fills data gaps of a key

life history component, and will be useful for future stock assessments.