Suitability of Insulin‐Like Growth Factor 1 (IGF1) as a Measure of Relative Growth Rates in Lingcod

Abstract

AbstractThe effectiveness of spatial management strategies is typically evaluated through traditional biological measurements of size, density, biomass, and the diversity of species inside and outside management boundaries. However, there have been relatively few attempts to evaluate the processes underlying these biological patterns. In this study, we take the first step toward developing a relative index of body growth for lingcod Ophiodon elongatus using plasma insulin‐like growth factor 1 (IGF1) with the ultimate goal of measuring spatial differences in relative growth rates. Insulin‐like growth factor 1 is one of the principal hormones that stimulates growth at the cellular level in all vertebrates and shows significant relationships with body growth in many fishes. In the laboratory, we found that the level of IGF1 was related to the instantaneous growth of juvenile lingcod. In the field, we measured size, condition, and plasma IGF1 level in 149 lingcod from eight locations inside and outside marine protected areas in the San Juan Islands, Washington. The IGF1 levels in wild lingcod were highly variable from site to site for both genders, and we were able to detect differences in IGF1 across space in males. Multivariate analyses showed that the spatial patterns of IGF1 differed from those of traditional biological measurements. More work is needed to validate the relationship between IGF1 and growth in larger individuals, but our research shows the potential for IGF1 to be used as an ecological indicator.