Low contemporary effective population size detected in the Critically Endangered giant sea bass, Stereolepis gigas, due to fisheries overexploitation

The giant sea bass, Stereolepis gigas (Polyprionidae), is the largest teleost distributed in the northeastern Pacific from California to northern Mexico and has been overexploited by fisheries for more than a century. As a consequence of this historic exploitation, populations collapsed throughout the region in the last century resulting in the listing of the species as Critically Endangered by the IUCN. Recently, numbers of giant sea bass have been increasing within the region due primarily to the banning of the near shore gill net fishery in California waters in 1994. To assess population structure, the impact of historic exploitation on the genetic diversity and effective population size of the species, and to detect signs of recent population expansions, individuals from throughout the northeastern Pacific (n = 61; Northern Channel Islands, CA to San Quintín, Baja California) were sequenced at the mitochondrial control region and genotyped using 12 nuclear microsatellite loci generated from next-generation sequencing. Based on these markers, a single population was detected with low genetic diversity resulting in an estimated contemporary effective population size of less than 500 individuals with evidence of recent expansion within the region.