Long days were the norm this past summer for graduate students Theresa Bersin and Ellie Brauer of California Polytechnic State University (Cal Poly), San Luis Obispo, as they conducted research on Pacific rockfishes supported in part by a Small Project Grant from the AFS Cal-Neva Chapter. Assisted by undergraduate students Katie Saenger and Grace Willett also from Cal Poly, Theresa and Ellie collected blood from wild juvenile blue rockfish (Sebastes mystinus) with intent to derive growth rate measures from the amount of insulin-like growth factor-1 (IGF1) present in each fish.
In fish, the hormone IGF1 is released into the blood stream to stimulate growth after food is consumed. The concentration of IGF1 in blood circulation relates positively to a fish’s recent foraging success and rate of growth, such that quantifying IGF1 in just a single sample of blood can provide a non-lethal, relative measure of a fish’s growth rate. This novel physiological approach hasn’t yet been applied broadly to wild fish populations but has the potential to provide growth rate data useful to fisheries management. By analyzing IGF1 concentrations in small samples of blood collected from blue rockfish, Theresa and Ellie are working to link individual growth measures in rockfishes to fine scale, nearshore habitat mapping along a section of the California’s Central Coast. This summer’s research was one part of a larger project of a team led by project PIs Sean Lema (Cal Poly) and Brian Beckman (Northwest Fisheries Science Center, NOAA Fisheries) aimed at using IGF1-derived growth rate data to improve our understanding of how rockfish growth is affected by variation in local ocean conditions.
Theresa Bersin and Ellie Brauer
Photo: Graduate student Theresa Bersin (second from right) and undergraduate student Grace Willett (right) collecting blood from blue rockfish with the help of volunteer fishermen.