Achieving sustainable fisheries in California depends on our ability to accurately assess population productivity in fishes. Historically, evaluations of productivity have relied heavily on measures of fish abundance; however, growth rate could also be used as part of a comprehensive approach to test the relationship between fish growth and environmental conditions (e.g., habitat, oceanographic parameters). When examined together, this information may be used to help marine resource managers better understand the drivers of productivity for marine fishes. The hormone insulin-like growth factor – 1 (IGF1) has been shown to be a reliable blood-based physiological biomarker for growth rate in marine fishes. We collected blood samples from Blue Rockfish (Sebastes mystinus) from two different Marine Protect Area (MPA) and non-protected locations along the central coast of California from 2016 through 2018, and then quantified the hormone IGF1. Preliminary analyses indicate that there is significant interannual and spatial variation in IGF1, suggesting variation in growth. Subsequent analyses will explore correlations of spatial and temporal variation in rockfish IGF1 to environmental conditions to explore effects of habitat and oceanographic variability on rockfish growth. Further understanding the relationships between environmental conditions and fish growth rates has the potential to improve management of economically and culturally important nearshore marine fishes.