Biologia reprodutiva da tainha Mugil liza Valenciennes e do Parati Mugil curema Valencienns (Actinopterygii, Mugilidae) na Baia de Sepetiba, RJ, Brasil

Abstract

The reproductive biology of the mullets Mugil curema and Mugil liza was determined mainly by observing gonad development, size at maturation and fecundity. The objective of this study was to learn about the strategies developed by these species to maintain their exploited populations in an increasingly altered system. It was hypothesized that there are differences in reproductive strategies, such as in reproductive timing, in order to avoid larval competition allowing highest survivorship rates of offspring in this environment. Fishes were collected from commercial catches from a tropical Bay in southeastern Brazil during July 2006 to June 2007. Spawning time was determined by observing macro and microscopic gonadal stages and the gonadosomatic index (GSI). Females were larger than males; the sex ratio was female-biased for sizes large than 275 mm and 500 mm total length (TL) for M. curema and M. liza, respectively. The populations reached reproductive activity (L100) at 260 and 310 mm TL for males and females M. curema, respectively and 550 mm and 570 mm TL for males and females M. liza, respectively. Mugil curema has a wide spawning season from August to January. Fish with mature gonads were present between August and January. The GSI had the highest values in September and October, prior to the rainy season. Mugil liza spawning season is from May to August and fish with mature gonads also were present at this period and the GSI picked in June. The hepatosomatic index (HSI) was significantly related to the GSI, indicating that vitellogenesis mobilizes hepatic energy during the spawning season. Mean fecundity was found to be 415,000 (± 32 x 103) and 3,080,000 (± 104 x 103) oocytes for M. curema e M. liza, respectively. The presence of only two phases of oocyte development in ripe ovaries a reserve stock and a clutch of post-vitellogenic oocytes indicated that ovarian development is group synchronic, and these species are total spawner. The hypothesis was confirmed, therefore, there are differences in the reproductive strategies and tactics of these species such as segregation in reproductive timing, fecundity and oocytes size, tatics that allow higher rates of prole survival and avoid larval competition.