Efeitos diretos e indiretos das medidas e razões morfométricas sobre os rendimentos corporais de tilápia do nilo (Oreochromis niloticus)

Abstract

The work was carried out in order to assess the measures and morphometric ratio are more directly associated to body income of Nile tilapia Oreochromis niloticus in two weight classes. Data were analyzed from 257 specimens of Nile tilapia, divided into two weight classes: P1 = 400 to 599 g and P2 = 600 to 900 g. The morphometric measurements were used: standard length (SL), head length (HL), body height (BH), and body width (BW) and the ratios of these measures (HL/SL, BH/SL, BW/SL, HL/BH, BW/BH, BW/HL). The income bodies were calculated: carcass (ICAR), fillet (IFILLET), head (IHEAD). The data were initially submitted to the procedure "Stepwise", aim to eliminate problems of multicollinearity among the morphometric variables, then were calculated the phenotypic correlations among the dependent variables (incomes body) and the independent variables (measured and morphometric relations). Later these correlations were divided into direct and indirect effects through path analysis and the direct and indirect contributions of each variable measured in percentage terms. It was observed that the morphometric ratio BW/HL, for both classes weight, was the variable most strongly correlated and direct effect on IFILLET and IHEAD, and when the larger ratio BW/HL greater IFILLET and minor IHEAD. The morphometric measures and ratio studied, in general, had low correlation with the ICAR, except SL that show most correlated (-0.65) and direct effect in the weight class P1 verifying that as higher SL minor ICAR. It is concluded that, the morphometric ratio BW/HL can be used as indirect measure of income IFILLET and IHEAD.