Genetic population structure of the critically endangered stellate sturgeon (Acipenser stellatus) in the Black Sea basin: Implications for conservation

Abstract

Stellate sturgeon (Acipenser stellatus) is a species of great conservation concern throughout its range. Over the past century, it has experienced a dramatic decline in abundance and distribution in the Black Sea basin. Information regarding the genetic structure of the species is very limited in the region, despite its crucial importance for developing adequate management plans for the species’ conservation and recovery. Samples from 163 A. stellatus were analysed using mitochondrial and microsatellite DNA markers to investigate the species’ genetic characteristics in the north-western and southern Black Sea. Both genetic markers revealed high genetic diversity (153 haplotypes and 264 alleles) and low genetic differentiation of marine and freshwater catches. The north-western Black Sea population is undergoing a slight demographic expansion after a bottleneck event induced by overfishing and dam constructions. The genetic population structure indicates a single genetic cluster in the north-western Black Sea region and signs of admixture of two genetic clusters in the southern region. It also provides the first evidence for a remnant reproductive stellate sturgeon micro-population in rivers of Turkey and Georgia. A sturgeon fishing ban and stocking activities carried out during the last decades, largely without any prior genetic assessment of the sturgeon populations, added little conservation value. Outreach initiatives and urgent actions are required to foster the recovery of this Critically Endangered species in the region. Reconstruction of the connectivity of the rivers and the enhancement of habitats and spawning grounds are beneficial to all sturgeon species. An ex-situ conservation programme for Turkish rivers which flow into the Black Sea would be beneficial to help conserve the genetic resources until the habitats and migration routes become functional. Moreover, genetic screening and recruitment programmes must be functional for all rivers flowing into the Black Sea.