Reproductive biology of the blue crab Callinectes sapidus on the Patos Lagoon estuary, RS, Brazil

Abstract

In this study, the reproductive state and the gonad relations of Callinectes sapidus were determinated on the estuary and oceanic adjacent area on the Patos Lagoon, RS, Brazil, from catch per unit of effort and fecundity data. Monthly samples were collected from April of 2008 to April of 2010. The size of carapace at first maturation (LC₅₀) of the blue crab was estimated in 108 mm for males and 115 mm for females. There was an increase in the gonadosomatic relation during winter months, and a decrease during summer months. The gonad relation allows inferring that the copula and gonad development is delimited between winter and spring. Through the analysis of the proportion of gonad development stage, the majority of the females from the beginning of winter presented immature gonad, whereas in the summer, the majority of analyzed females had gonad in rest, indicating recent spawning. The species presents a well marked seasonal reproduction for the estuary, with males maturing at a smaller size than females. In the reproductive season of 2008, there was a balance between the sex ratio, which was not repeated in the 2009 season. It is possible that such phenomenon occurs due to the high volume of rainfall recorded during that period, causing migration of females to higher salinities for spawning. Callinectes sapidus is sensitive to environmental alterations, and longer periods of rainfall combined with other factors like low salinity and temperature can endanger future breeds.