Reproductive Variance of Brood Dams and Sires used in Restoration Enhancement of Spotted Seatrout in Texas Bays and Estuaries

Abstract

AbstractSpawning patterns and reproductive variance of Spotted Seatrout Cynoscion nebulosus dams and sires at two restoration enhancement facilities in Texas were assessed across a spawning year by using parentage analysis based on 12 variable microsatellite loci. In total, 72.6% of all dams and sires contributed to at least one spawning event, although in contrasting patterns. Across all spawning events assayed, more sires contributed to each spawn, on average, than did dams; dams had considerably higher variance in reproductive success than sires. Dams alternatively had a higher average contribution to the number of progeny from a single spawn but also a much higher variance in the number of progeny produced per spawn. The variation in the number of progeny produced per dam and per sire and the number of actual mating combinations led to an average reduction of 64.3% in the genetic effective population size (Ne) per spawn relative to the maximum Ne that would be expected if (1) all possible dam × sire mating combinations occurred at random and (2) all families contained an equal number of progeny. Averaged over all spawns, the actual number of mating combinations accounted for approximately 83.6% of the total reduction in Ne, while variation in family size accounted for 16.4% of the total reduction in Ne. Results from this and other studies indicate that reductions in Ne of hatchery‐ or farm‐raised progeny stem primarily from noncontributing dams, suggesting that periodic identification and removal of low‐contributing dams from broodfish stocks constitute a critical step toward maximizing the Ne of hatchery offspring used in restoration enhancement.