Meeting Abstract
Nutritional stress affects somatic growth in part by altering the expression of hormones in the somatotropic endocrine axis such as insulin-like growth factor-1 (Igf-1). In this study, we examined how the Igf system responds to variation in food availability in juvenile copper rockfish, Sebastes caurinus, a nearshore Pacific rockfish species important for both recreational and commercial fisheries. By regulating food rations, we created groups of copper rockfish with higher or lower growth rates. After 140 d under these rations, some rockfish from both growth treatments were fasted for 12 d, while other fish continued to be fed. As expected, juvenile rockfish in the high ration treatment grew more quickly (avg. length specific growth rate [SGR]: 0.114% per d) than those in the low feed treatment (SGR: 0.055% per d), so that high ration fish were larger in mass and length and had a higher body condition (k). Fish from the high ration treatment also had higher blood glucose concentrations than those under low ration, and fish from both ration treatments that were fasted had lower blood glucose than those that continued to be fed. Rockfish that grew more slowly from reduced rations had a lower relative abundance of gene transcripts encoding igf1 in the liver, but elevated hepatic mRNAs for Igf binding proteins igfbp1a and igfbp1b. Fasting decreased the abundance of igf1 mRNAs in the liver in both growth groups, while concurrently increasing igfbp1a and igfbp1b mRNAs over 3-fold. These results point to changes in Igf signaling as contributing to the reduced growth that Pacific rockfishes exhibit under conditions of limited food abundance.
