Genetic Identification of Hatchery‐Released Red Drum in Texas Bays and Estuaries

Abstract

The stock enhancement program for red drum Sciaenops ocellatus in Texas annually releases from 25 to 30 million fingerlings into Texas bays and estuaries and represents one of the largest such programs for marine fishes worldwide. We used 16 nuclear-encoded microsatellites and a 370-base-pair fragment of the mitochondrial DNA (mtDNA) D-loop to assign red drum sampled from two bays along the Texas coast to either hatchery or wild origin. A total of 30 hatchery-released fish were identified among 321 red drum belonging to three year-classes sampled from Galveston Bay, while a total of 11 hatchery-released fish were identified among 970 red drum belonging to four year-classes sampled from Aransas Bay. Allelic richness (microsatellites) was significantly lower among hatchery-released fish than among hatchery broodfish and wild fish. Similarly, the expected number of mtDNA haplotypes in hatchery-released fish (based on simulation analysis) was significantly lower than that expected in a random sample of both brood and wild fish. The contribution of brood dams, sires, and dam 3 sire combinations to the hatchery-released fish was nonrandom, as was the distribution of hatchery-released and wild fish with respect to sampling stations (localities) within each bay. The possibility of a Ryman-Laikre effect is discussed.

Compromising genetic diversity in the wild: unmonitored large-scale release of plants and animals

“…Hatchery fish had habitat usage similar to wild fish in Florida [74] but not in Texas [69]. Hatchery releases comprised an estimated 1-12% of the wild population in Texas and Florida and up to 78% in South Carolina [69,73]. In Texas, adults used for broodstock had comparable levels of genetic diversity to wild fish, but released fish had lower genetic diversity [69].…”

“…Large enhancement efforts have been conducted for over two decades for red drum (Sciaenops ocellatus) in both the Gulf of Mexico and the Atlantic. As many as 25-30 million fingerlings are released each year in Texas alone [69]. State-of-the art genetic monitoring programs associated with these enhancement efforts have provided key information about effects on natural populations:…”

“…Estimated N e for local populations is roughly 10 2 -10 3 compared to a census size on the order of 10 6 adults [70][71][72]. Individual broodstock programs typically use 40-200 adults [71][72][73], but non-random contributions of different parents leads to relatively low hatchery N e [69,71,72]. A detailed study of one Texas hatchery in one year estimated the hatchery N e to be 28-47 [71].…”

“…A detailed study of one Texas hatchery in one year estimated the hatchery N e to be 28-47 [71]. Hatchery fish had habitat usage similar to wild fish in Florida [74] but not in Texas [69]. Hatchery releases comprised an estimated 1-12% of the wild population in Texas and Florida and up to 78% in South Carolina [69,73].…”

“…Hatchery releases comprised an estimated 1-12% of the wild population in Texas and Florida and up to 78% in South Carolina [69,73]. In Texas, adults used for broodstock had comparable levels of genetic diversity to wild fish, but released fish had lower genetic diversity [69]. No reductions in levels of genetic diversity were detected in wild populations [70].…”