This project examines effects of ocean acidification (as simulated by elevating pCO2 levels) on swimming physiology, behavior and gene expression patterns of early post-settlement rockfishes found in Central California’s kelp forests and rocky reefs. Manipulation experiments are being conducted at the Monterey Bay Aquarium Research Institute to compare the effects of ocean acidification on rockfish species that recruit during periods of strong and weak upwelling. The hypothesis is that juveniles (2–4 centimeters in length) exposed to more acidic waters, consistent with climate-change scenarios for 2050 and 2100, will have an impaired ability to distinguish the odors of predators and, as a result, will show reduced problem-solving abilities. Researchers will also examine consequences of elevated pCO2 conditions on juvenile fishes’ swimming speeds and aerobic performance (e.g., respiration rates). In the genetics component of the project, they will develop assays to characterize changes in the expression of genes involved in olfaction, acid-base regulation, cellular stress response and protein biosynthesis in fishes exposed to ambient and elevated pCO2 levels. A secondary hypothesis being explored is that species recruiting in spring may be more adapted to variable pH-conditions associated with seasonal upwelling of deeper, more acidic waters. In the past year, researchers have found that copper rockfish (which recruit in spring) are much more sensitive to more acidic conditions than blue rockfish (which also recruit in spring). In the coming year, they plan to finalize results of gene expression assays and they will conduct experiments with additional rockfish species to better understand species-specific sensitivities to elevated pCO2. Results will be shared with federal and state fisheries agencies involved with managing groundfishes.