IDENTIFICATION OF SPRING AND FALL SPAWNED EGGS AND THE GENETIC DISTINCTION OF GULF STURGEON IN THE CHOCTAWHATCHEE RIVER, ALABAMA-FLORIDA
The Gulf Sturgeon (GS; Acipenser oxyrinchus desotoi) is a threatened subspecies of Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus) which inhabits the Gulf Coast of the United States. Prior studies of Eurasian sturgeon species and Atlantic Sturgeon have revealed the existence of a dual spawning strategy (i.e. spring and fall). The presence of a fall spawn has also been proposed for GS, but only with the support of circumstantial evidence. This study used molecular techniques to investigate seasonality of GS spawning and the possibility that this has produced unique genetic groups in the Choctawhatchee River. Mitochondrial DNA from suspected GS eggs was used to verify the presence of a dual spawn. Microsatellite genotypes were used to characterize and quantify the extent of differentiation of genetic groups in the population. Egg samples were collected in spring and fall seasons of 2019 and 2020. Adult fin clips were collected in late summer and fall of 2018 to 2021. A total of 381 eggs were collected and sequences for 74 of these were confirmed as GS when compared to known haplotypes. STRUCTURE analysis of microsatellite genotypes identified two distinct genetic groups, presumably representing spring and fall spawning groups. Most individuals strongly assigned to a particular group with 44 fish identified as spring spawners and 67 as fall spawners. Only three individuals showed admixture between the two groups. The verification of a second spawn can have significant effect on how the species’ recovery is managed.
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