Aspectos da biologia reprodutiva e padrões de crescimento da tilápia Oreochromis niloticus, Linnaeus,1758, (Linhagem Chitralada) em cultivos experimentais

Abstract

This work was accomplished in the Aquiculture Experimental Station belong to the Fisheries Department of the UFRPE and in the Fish culture Station of CHESF, Paulo Afonso-BA, in the period between the year of 2001 and 2002. Aimed to study some aspects of the reproductive biology of the Nile-tilapia, Oreochromis niloticus, chitralada strain, and the patterns of growth of its offspring in different experimental conditions. Initially, it was investigated the growth performance among sexually reverted and no-reverted fish, in two offspring strains with patterns of growth denominated type A and B. These offspring were a result of the breeding crossing between the broods fish, having the following patterning of growth: ♂A X ♀A and ♂A X ♀B. First, the growth was compared among the reverted fish and no-reverted ones, inside of each group and between them; a intra and inter-specific comparisons. Soon after, it was observed the growth of the successive strains from non-reverted fish stocks, a comparative study of the growth between males and females, and finally, the study of the sexual proportionality from the same spawned fish. According to the results, there was not significant difference (P=5%) among reverted fish and no-reverted ones, as for the intra-groups (A with A and Bwith B) as well for the inter-group comparison (A and B). There was no statistical difference among the offspring F1 and F2 of no-reverted fish, and between the males and females, when they were cultivated in tanks. There was a difference in growth when the males cultivated in earthen pond were compared with those females reared tanks. Males were larger, statistically,. With relationship to the sexual proportionality inside spawning, it was noticed that the male was more predominant than the female, in a sexual proportion that varied among 4:1 - 2:1. It could be concluded that non-reverted fish grew as much as the reverted ones, in consequence of two factors: 1) the females grow as much as the males and 2) the number of males is always predominant over females in any spawning. The variables physical-chemistries of the water were considered in the normal conditions for the practice of fish culture. The group of tilapia Chitralada here investigated is a strong candidate for the program of species selection based on AGV (Additive genetic variation), done in several parts of the world. It is recommended the effective control of this tilapia strain and wider scientific observations, in order to verify the continuous effect of theresults obtained in this work.