Biologia reprodutiva do peixe tetra splash Copella arnoldi (Regan 1912) em uma bacia do atlântico noroeste ocidental

Abstract

Fish that spawn in the terrestrial environment tend to have a higher energy expenditure against the risk of dehydration of eggs and the degree of survival of juveniles, eventually adjusting their reproduction to the hydrological conditions of the environment. Therefore, the present work had the objective of analyzing the influence of precipitation on reproductive aspects of tetra splash Copella arnoldi on the Taiassuí river, in a basin of Northwest Atlantic West, Pará State, Brazil. A total of 171 specimens were collected in bimonthly campaigns from August 2016 to June 2017, in laboratory standard length and total weight were evaluated, then the specimens were eviscerated for later weighing and analysis of the gonads. The gonads underwent histological routine to determine the stage of gonadal development. The mature gonads were placed in Gilson's solution and dissociated to obtain the data of fecundity and type of spawning. On average, each mature female of C. arnoldi. possessed 85 oocytes; the lowest and highest oocyte diameter frequency was in the 700-300 μm class, respectively; the modal type distribution indicates a total spawning. The L50 was estimated at 18.09 mm for females and 18.52 mm for males. The weight-length relationship indicated that females and males tend to grow in equal proportions of weight and length. The condition factor did not change in relation to the rainfall cycle, although slightly higher values were observed during the dry season. The sex ratio remained the expected (1: 1) throughout the study period, however during April and August there is a predominance of females in the population. The spawning period of C. arnoldi appears to be associated with the rainy season, since two reproductive peaks can be observed in December (early rainy season) and April (month of higher precipitation). Thus, we show that C. arnoldi synchronizes spawning with the rainy season probably due to a lower risk of egg dehydration and greater survival of juveniles.