Genetic population structure of the commercially most important demersal fish in the Southwest Atlantic: The whitemouth croaker (Micropogonias furnieri)

•Three different stocks of M. furnieri were found in Brazil using molecular markers.•One stock occurs in North Brazil, another off Rio and other in south Brazil.•There is an admixing zone between Rio and the South, which follows an IBD model. The whitemouth croaker (Micropogonias furnieri) is the main fish species of the demersal fisheries along the Atlantic coast of South America. There has been much debate regarding the number of stocks of this heavily exploited fish off the Brazilian coast between latitudes 23°S and 33°S. Analyses of morphometric and meristic data suggest that two stocks exist in that area, but this conclusion was not supported by genetic studies. Here, we used polymorphic nuclear loci (microsatellite and intron size polymorphisms) to compare samples of M. furnieri collected between Rio de Janeiro (23°02′S) and Chuí (33°41′S), as well as samples from much further north, along the coast of Bragança at Pará State (1°03′S). Our data demonstrate the existence of three distinct stocks of the species in Brazil: one in North Brazil (Bragança – Pará State), as previously suggested; and two previously not detected genetically: one between 23°S and 29°S; and another south of parallel 29°S. These findings indicate that the fisheries of the three areas should be managed as distinct stocks.