Population dynamics of the crab Hepatus pudibundus (Herbst, 1785) (Crustacea: Decapoda: Aethridae) in the Cananéia region, extreme south of the São Paulo State

Author(s)

Lizandra Fernandes Miazaki

• Document type: Master's Dissertation
• Press: Botucatu. 2017-05-03.
• Institution: Universidade Estadual Paulista (Unesp). Instituto de Biociências. Botucatu
• Defense date: 2017-02-20
• Advisor: Rogério Caetano Costa; Sabrina Morilhas Simões

Abstract

The crab Hepatus pudibundus is wide distributed in the Brazilian coast. The species has no commercial value but is intensely captured as bycatch of penaeid shrimp fishery, so it suffers the same impacts of the target species. In this view, the present study investigates the population dynamics, focusing on the following aspects: sex ratio, morphological sexual maturity and gonads, reproductive period, juvenile recruitment, growth and longevity of individuals. Sampling was performed monthly in the region of Cananéia/SP, from July/2012 to June/2014 in seven stations, with a shrimping boat equipped with otter trawl nets. Temperature and salinity of the bottom water, the organic matter content, sediment granulometry and rainfall were investigated. A total of 1,650 specimens were captured. Males were larger than females. The sex ratio skewed towards females. The estimated sizes for morphological and gonadal sexual maturity (CW50) were 42.26 mm and 48.97 mm for males, and 43.09 mm and 47.15 mm for females, respectively. Reproductive females occurred throughout the studied period and juveniles were captured in most months. Such demographic categories were positively correlated with temperature. Growth parameters showed differences between sexes: CW∞ = 78.91 mm, k = 0.0066/day, t0 = 0.0965 for males and CW∞ = 67.68 mm, k = 0.0064/day, t0 = 0.0032 for females. Longevity was estimated at 1.91 years and 1.98 years for males and females, respectively. The sexual dimorphism found in this study is possibly related to behavioral differences between males and females. The sex ratio skewed towards females may be related to different growth and mortality rates, food restriction and different use of habitat for each sex. The estimated values for morphological maturity were higher for females, which favor the reproductive success of the species; females with a larger cephalothorax cavity can produce and externalize a higher number of eggs in relation to minors. In contrast, the size of gonadal maturity estimated was higher in males, which may also be favorable to the reproduction of the species; larger males are in advantage when protecting and manipulating the female during copulation. The results suggest a continuous reproduction and recruitment, which are typical of warm tropical and subtropical regions, corroborating the paradigm of latitudinal effect as well as the parameters of growth and longevity. The data presented provide a greater understanding of the life cycle of the species. Additionally, since trawl nets are not selective, this study also provides information for a better trawl fishery management, addressing not only the target shrimp but also the bycatch species. (AU)

• FAPESP's process: 15/20382-0 - Population dynamics crab Hepatus pudibundus (Herbst, 1785) (Crustacea, Decapoda: Aethridae) in the region of Cananéia, extreme south of São Paulo, Brazil
• Grantee: Lizandra Fernandes Miazaki
• Support Opportunities: Scholarships in Brazil - Master