experimental assessment of genetic tagging and founder representation in hatchery-reared red drum (Sciaenops ocellatus) used in stock enhancement

Multiplexed microsatellite markers were evaluated as genetic tags for red drum (Sciaenops ocellatus) juveniles used in stock enhancement. Offspring were generated from spawns of nine sets of five broodfish (three dams and two sires) in individual brood tanks. Intensive sampling, by trawling, at 2, 7, 8, 10 and 11 days after release of ~192 500 hatchery-raised fingerlings resulted in recovery of a total of 310 fingerlings. All parents and recovered offspring were genotyped for variation at 30 microsatellites combined for simultaneous assay in six multiplex panels. An optimal combination employing three of the six multiplex panels allowed unambiguous parentage assignment of all recovered offspring. Only 21 of 52 possible dam x sire combinations were represented among recovered offspring. The founder equivalent (fe) of the recovered offspring was 8.7 vs the expected fe of 36.0 (95% CI = 33.3-38.4) if reproductive success was randomly distributed among breeders. The significantly lower founder equivalent translated into reduced genetic diversity among the recovered offspring and may reflect differing contributions of individual broodfish to spawning events, differing productivity among brood tanks, and/or variable survival of families during early larval and/or juvenile stages.