Using mark–recapture information to validate and assess age and growth of long-lived fish species

Abstract

Long-lived species from marine and freshwater environments have experienced declines linked to anthropogenic effects such as overexploitation, dam construction, and habitat modification. An understanding of the age structure and the associated dynamics determined from these data for long-lived species is critical for both perseverance of at-risk species and maintenance of exploited species. We used pallid sturgeon (Scaphirhynchus albus) to evaluate the efficacy of mark–recapture data from known-age, hatchery-reared fish (ages 1 to 7) to corroborate age and growth estimates obtained from sectioned pectoral fin rays. Accuracy of age estimates from known-age fish was 13%, whereas 72% of estimates were within 2 years of the true age. Annual growth was significantly different between estimated growth (back-calculated) and actual observations of tagged pallid sturgeon. Age for pallid sturgeon of any given size was estimated with parameters derived from mark–recapture data, and the predicted length-at-age relation was similar to observations from known individuals. In instances where age determination for all ages of interest cannot be verified, mark–recapture appears to be a viable solution for examining growth and has shown promise as a tool for estimating ages in long-lived species with calcified structures that are difficult to read.