Morphometric discrimination among three stocks of Macrobrachium amazonicum in the Brazilian Amazon

The aim of this study was to compare stocks of Amazon River prawns (Macrobrachium amazonicum) among 3 sampling sites (Tucuruí, Cametá and Soure) in the Tocantins/Araguaia River Basin (Amazônia, Brazil) through morphometric analyses. A total of 360 specimens (180 males and 180 females) were sampled, and 21 morphometric characters were assessed and subsequently analyzed using descriptive and multivariate statistics. Principal component analyses showed a strong ability to distinguish the different stocks, especially between those at the sites most distant from each other (Tucuruí and Soure). In the discriminatory analysis, the most significant characteristics for females were total length (TL), carapace width (Cw) and palm width (Pw), whereas for males, the most significant characteristics were Pw and Cw. The cluster analysis showed different groupings for the male and female models, although the Tucuruí and Soure stocks were always separated. Therefore, the multivariate analyses identified 3 different stocks in the sampled area, and an explicit fishing management plan for each stock is suggested because this species has been shown to be imminently threatened by overfishing in the Amazon region.