The arapaima, an emblematic fishery resource: genetic diversity and structure reveal the presence of an isolated population in Amapá

The arapaima ( Arapaima gigas ) is one of the most emblematic species of the Amazon region, and has a long history of exploitation. The present study investigated the connectivity and genetic variability of the arapaima in the region of the confluence of the Amazon and Araguaia-Tocantins basins, with emphasis on the population from the Lago Piratuba Biological Reserve, in the Brazilian state of Amapá. The study was based on the analysis of 11 microsatellite loci and the mtDNA control region sequences of 114 arapaima collected at six localities in the region of the eastern Amazon. The genetic analysis found significant differentiation, which indicated the presence of three distinct populations, the Lower Amazon-Marajó, Lago Piratuba, and Lower Tocantins populations, which lacked any significant level of gene flow. All three populations presented evidence of recent bottlenecks and distinct levels of genetic diversity, which was high only in the Lower Amazon-Marajó population. The conservation strategies for this region should consider the specific characteristics of these three populations and the different patterns of diversity found. The genetic characterization of the Lago Piratuba reserve as a unique population reinforces the importance of the implementation of adequate management strategies in the region.