Crescimento morfométrico e alométrico de linhagens tilápia ( Oreochromisniloticus)

Abstract

The objective of this research was to study the morphometric and allometric development and evaluate the yield of processing of tilapias meat in function of the body weights on two strains: Chitralada (or Thai) and Supreme. This experiment was carried out at the Fish Culture of the Animal Sciences Department, Federal University of Lavras, M.G. - Brazil. Different morphometric measurements and their relations, and variables as the volume of the body (VBODY) and the area of the skin (AS) were measured. Growth curves in function of fish weight were fitted according to function of Brody (1945). For the morphometric growth, the Supreme strain presented higher limiting values for standard length (SL) and body width (taken in the first ray of the anal fin - BW2), higher growth rate of body perimeter (taken in the first ray of the dorsal fin and in the tail) and higher width/SL and perimeter/width relations. These variables indicate that Supreme strain has a cylindrical format of their muscles and consequently, a larger fillet yield, compared to Chitralada strain. The correlation between these variables, carcass yield and fillet yield were higher for Supreme strain compared to Chitralada. The strain Chitralada presented higher limiting values for the body height (taken in the first ray of the dorsal and anal fin), higher growth rates for SL and a reduction rate on head's length (HL) in relation to SL. The Supreme strain also presented smaller limiting value for the percentage of visceras and also larger carcass yield and fillet yield, being more expressive in body weights superior to 500 g. The allometric growth of the fillet was heterogonic and later in age in both strains. The morphometric measurements and their relations showed low correlation with carcass yield (YCAR) and with fillet without skin (YFWS) yield, in both strains. In Chitralada these correlations did not exceed 30 %, and the largest values were found for HL (negative correlation) and BW2/SL (positive correlation) in relation to YCAR. The VBODY had the largest correlation coefficient with fillet yield in Supreme strain (0,586). All morphometric measurements had high correlations (in most of the cases above 90 %) with both carcass and fillet weights. The variable AS had the highest correlation (about 96 %) in the two strains. It was concluded that there in difference in the morphometric growth between the two strains. The VBODY and AS are measurements that can be used in selection programs. Carcasses with smaller height/width, perimeter/width relations and with larger width/length and perimeter/height relations are more suitable for commercialization, as this can indicate larger eatable parts yield. Selection programs improving meat yield selected by measurements and morphometrics relations should be made differently for each tilapia strain.