Efeito da época da indução hormonal sobre a qualidade da desova em matrinxã (Brycon amazonicus)

Abstract

The objective of this study was to identify the effects of the season of hormonal induction on the quality of spawning in matrinxã (Brycon amazonicus). The females used in this experiment were selected from the group at Fazenda Santo Antonio, Rio Preto da Eva/AM, which was maintained at six ponds with an average size of 1,000 m2 and an average depth of 1.6 m each. The previous conditioning pond were divided by nets of plastic fiber, so that the number of catches in trawls was halved, reducing the impact on the harvest entire lot. Between the months of February and August, the latent period for gonad maturation of matrinxã, females were subjected to a stocking density of one breeder per 10 m2 and fed commercial extruded feed containing 40% crude protein, one day each two to 1.5% of biomass. The experimental period began on September 13th with the selection and induction of the first group of breeders and ending on November 18th with the extrusion of oocyte fertilization of the last females chosen for the experiment. After spawning were collected biometrics data (weight and length) and fecundity (egg production) and these reproductive data enabled the characterization of the influence of biometric variables on fecundity relative and absolute, identifying the ideal time for artificial reproduction of breeders, characterization of the influence of edaphoclimatic conditions [atmospheric temperature data (° C) and precipitation (mm)] on relative and absolute fecundity and evaluation of the condition factor as a tool for selection of matrinxã breeders. At the experiment ending, 59 females (average weight 1315.9 ± 307.04 g) spawned 7,057 g of oocyte mass. The weight.lenght-1 relation of females was positive (y=0,1653x2,5067; R2=0,8126). The average productivity of eggs per female was 119.61 g, almost 10% of the live weight of animals. Relative fecundity was important to estimate the time of the year most productive in relation to the number of eggs produced. There was little interaction between fecundity and weight and length, but the closer to the end of the experiment (November) was most the power of interaction between the relations. The edaphoclimatic conditions influence the spawning of matrinxã (p<0.05), with the wettest months tend to have better spawns. For the condition factor (Kn) statistical differences were found in relation to the central value (Ho: Kn = 1.0, α = 0.05), however, do not found direct relationship between the values of Kn and fecundity of animals. There was no statistical difference between the fecundity of females that showed Kn>1.0 (45.8% of females had an average fecundity of 126.4 g of eggs) and Kn<1.0 (54.2% of females had an average fecundity of 117.13 g of eggs), although females with Kn<1.0 present a greater deviation around the average fecundity. Among the months tested, the best month of the average relative fecundity was November.