Meeting Abstract
Currently, commonly used methods for quantifying individual growth rates of wild fishes require terminal sampling (otolith analysis), time consuming tagging (mark-recapture), or have limited value as indicators of somatic growth (RNA:DNA ratios). The development of rapid, non-lethal methods for quantifying growth rates is needed to provide data necessary for informed fisheries management. Blood hormone concentrations have shown to be accessible indicators of growth regulation and metabolism. Specifically, insulin like growth factor-I (IGF-I) has a low clearance rate and robust relationship to somatic growth in several fishes, making it a potential endocrine biomarker of specific growth rate for fisheries applications. Here, we tested whether plasma IGF-I concentrations could be used as a tractable indicator of somatic growth and nutritional status in Sebastes rockfishes, a group of species important to commercial and recreational fisheries on the Pacific coast of N. America. To test associations between IGF-I and growth rate, we collected juvenile olive rockfish (Sebastes serranoides) and yellowtail rockfish (Sebastes flavidus) from central California, USA, and reared them in captivity under food ration treatments of 1% or 4% wet mass per day to experimentally generate growth variation. We hypothesize that fish raised under higher rations will exhibit high plasma total IGF-I concentrations. We also hypothesize that hepatic mRNA levels for IGF-I (igf1) and IGF binding protein-1b (igfbp1b) will be elevated in rockfish exhibiting faster somatic growth. Linking concentrations of IGF-I to growth and nutritional status in rockfish could provide a non-terminal assessment of health for these over-harvested species.
