Date of Award


Degree Name

MS in Biological Sciences


College of Science and Mathematics


Sean Lema

Advisor Department

Biological Sciences

Advisor College

College of Science and Mathematics


Identifying areas of high fish population productivity is crucial for protecting habitats essential to fish growth and reproduction and, ultimately, for achieving sustainable fisheries. Historically, evaluations of habitat quality have relied heavily on linking spatial variation in fish abundance to environmental parameters such as substrate category, depth, or bathymetry. That approach, however, assumes that areas of high fish abundance best support growth and reproduction of a species and thus may fail to detect spatial or temporal variation in population attributes, such as somatic growth rate, which can be central to recruitment success and survival. In this study, we employed a novel physiological approach using the hormone insulin-like growth factor-1 (Igf-1) as a blood-based ‘biomarker’ for recent growth rate to determine patterns of spatial and temporal variation in growth of Blue Rockfish (Sebastes mystinus) along nearshore central California, USA. Blue Rockfish were sampled between 2016 and 2018 from two different regions ~60 km apart on the central coast of California: the Piedras Blancas region and the Point Buchon region. In each region, sampling was conducted in a Marine Protected Area (MPA) and in an adjacent non-protected area. In all years, Blue Rockfish in the Piedras Blancas region had consistently higher growth rates compared to the Point Buchon region. Yearly differences in average Igf-1 values were similar for fish collected from the Piedras Blancas and Point Buchon regions, suggesting that broad-scale, annual variation in food availability affects Blue Rockfish growth rates similarly across this geographic extent of the central California coast. While no consistent differences in Igf-1 were observed for fish sampled at protected MPA and adjacent non-protected areas, spatial variation on the scale of 500 m was observed across some sites sampled on the same day, suggesting that Blue Rockfish growth can vary substantially across even relatively constricted habitat locations. Temporal variation in growth rates was also observed on the scale of < 1 month across some sampling sites. These findings illustrate how Igf-1 can provide a tool for identifying recent growth rate variation in wild Pacific rockfishes with the potential to improve management of economically and culturally important nearshore marine fishes.