Reproductive aspects of “charal prieto” Chirostoma attenuatum (Meek, 1902) of lake Pátzcuaro, Michoacán. New topics on atherinopsids of México

Abstract

Some important reproductive aspects of charal Chirostoma attenuatum were analysed for the annual cycle 1988-1989 in Patzcuaro lake, related to the phases of gonadal maturation based in Nikolsky and Peralta maturation scales; the gonadosomatic index were obtained for the maturation phases analysed. The size of first maturation was obtained as well as the minimal maturation size which were obtained by inter and extrapolation on the whole sample of matured individuals, the sexual ratio and the sizes structure. The results show a wide reproduction period from January to September; a sexual reproduction ratio of 2-3 males per female. Through the analysis of the maturation phases in each station it was possible to determined that Urandén, Zacuapio y Pacanda are reproductions grounds and that Urandén and La Playa are growing grounds suggesting that these places should be considered as reserved areas for the protection of the specie. The first maturity size was 8.1 cm LS and the minimum maturity size 5.5 cm LS. It was found that the sexual ratio is different from 1:1 (p>0.05) and that there is a differential distribution of sexes in the lake. Differential sizes in males and females were found in spatial and temporal scales. Both sexual ratio different from 1:1 and differential sizes of males and females are associated with a mayor phenomenon of sexual determination by temperature. Reproductive ecology studies are needed for this and other species of Mexican atherinopsids in which sexual temperature determination would play an important role to the understanding and management of these resources.