Spotted seatrout (Cynoscion nebulosus) populations are vulnerable to catastrophic winter kills at least once a decade. Enhancing the wild spotted seatrout population with hatchery-raised stocks after those catastrophic kills requires a balance to ensure the ideal genetic diversity and population size for long-term species adaptability.
Hatchery managers have few established protocols for determining appropriate stocking numbers or evaluating the potential risks of stocking on the genetic health of the wild population. Researchers will compare stocking strategies at multiple population abundance levels to determine the best practices for spotted seatrout conservation efforts.
Project Findings
A total of 797 hatchery-produced spotted seatrout samples from 2014 and 2018 were genotyped to identify which parents contribute to spawning events and each parent pair’s proportional contribution to the total number of offspring, allowing for an improved understanding of the effective population size of hatchery-raised spotted seatrout.
Researchers utilized a new Python individual-based model (IBM), incorporating the improved hatchery effective population estimates, to guide management decisions for spotted seatrout and better understand the influence of stocking strategies on wild populations. Using this IBM, spotted seatrout’s life history and current genetic diversity in Charleston Harbor were found to provide them with high resilience to recover from population bottlenecks associated with cold winter events.
Researcher recommendations for a restoration stocking program for spotted seatrout experiencing a single cold winter kill event would include incorporating the SCDNR’s optimized hatchery production protocols to maximize genetic diversity of stocked fish, utilizing as many broodstock as possible, and restricting stocking to 200,000 juveniles or fewer per year.
Preliminary simulation results provide resource managers and stock enhancement research programs with quantitative tools that promote responsible recovery and management of spotted seatrout populations in the case of a future severe winter event in South Carolina or beyond.