Morfometria elíptica na predição de pesos e rendimentos corporais de tilápia do Nilo (Oreochromis niloticus)

Abstract

The Nile tilapia (Oreochromis niloticus) has low carcass yield, especially in terms of fillet, so it is necessary to study correlated variables that assist in indirect selection. This study aimed to evaluate the correlation of elliptical forms derived from primary morphometric measurements with the weights and yields of body components of Nile tilapia (Oreochromis niloticus) and their use in the indirect selection of commercially relevant carcass traits for genetic improvement purposes. Sixty families were used, and within each family, 40 animals with an average weight of 250 grams were randomly selected. Primary morphometric measurements, including standard length, width, and height, were obtained, along with animal weights: live weight, total fillet weight, loin fillet weight, and belly weight. Ellipticity and elliptical area were calculated from the collected primary morphometric measurements (height, width, and standard length). Pearson correlation analyses and linear regression analyses were conducted, with body component weights and body yields considered as dependent variables, and primary morphometric measurements, ellipticities, and elliptical areas as independent variables. Elliptical areas and primary morphometric measurements showed determination coefficients greater than 0.80 for the weight of clean total fillet and its subcuts. Elliptical areas also exhibited higher correlation values with body component weights than those presented by primary morphometric measurements. Elliptical areas adjusted the width to a shape closer to the real form of tilapia, making all planes good predictors for the studied weight range. Lateral elliptical area (LEA) showed the best R2, considering its formula accounts for the two main measurements affecting tilapia fillet: standard length and height. Prediction equations for yields had low R2 values (<0.31) for all morphometric measurements. Lateral, frontal, and dorsal elliptical areas (AEL, AEF and AED) had the highest correlation values and best fits for fillet weight prediction equations, proving to be better predictors than primary morphometric measurements. Lateral elliptical area (AEL) showed the strongest correlation with fillet weights (PFL) and the best coefficient of determination (R2 = 0.88). Therefore, the equation PFL = - 36.17 + 0.92 × AEL can be used as a predictor for the weight of clean total fillet.