Otolith chemistry can discriminate signatures of hatchery-reared and wild spotted seatrout

Abstract

A central goal of stock enhancement is to increase species abundance and potential harvest by supplementing recruitment of wild populations. The efficacy of these efforts is predicated upon the survival of these hatchery-reared organisms after release, and determining their fate is essential to understanding the success of these programs. Along the northern Gulf of Mexico, spotted seatrout (Cynoscion nebulosus) represent the number one recreational fishery and in Texas are stocked in coastal bays and estuaries to enhance natural fish abundance. The natural chemical properties of fish otoliths represent one mechanism to track the fate of hatchery-reared fish in the wild and make inferences about their movement and survival. Establishing a baseline signature pattern to discriminate hatchery-reared from wild fish is an essential first step in this process. Spotted seatrout fingerlings were collected from three Texas bays and three Texas saltwater fish hatcheries. Sagittal otoliths were analyzed for stable isotopes (δ13C and δ18O) and a suite of twelve trace elements. Multivariate and univariate analysis of variance tests indicated significant differences among natal origins and reduced the number of chemistry predictors to nine. Linear discriminant function analysis using jack-knife cross-validation successfully classified 92% of fish to their correct natal origin. These results show that otolith chemistry is a powerful tool for discriminating hatchery-reared from wild spotted seatrout; therefore, chemical signature patterns reflected in the otoliths establish a baseline for tracking the fate of hatchery-reared fish in the wild. This information can provide more quantifiable estimates of stock enhancement success to fishery managers by improving our understanding of the fate and contribution of hatchery-reared fish to wild populations.