Reproductive period and size at first maturity of Ucides cordatus Linnaesus, 1763 (Crustacea: Decapoda) in two mangrove of Maranhão, Brazil
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1
State University of Maranhão, Chemistry and biology, Brazil
Ucides cordatus, popularly known as “uçá”-crab, plays an important ecological role by actively working on nutrient cycling of mangroves. In Maranhão State, this species has been heavily exploited and some evidence of overfishing, as weight reduction and average size of captured specimens, are already observed. In recent years, research on the biology and ecology of this species have intensified throughout the coast of Brazil. There is still a deficit of studies that deal with their population and reproductive dynamics in Maranhão State. We then aimed to analyze aspects of reproductive biology Ucides cordatus in two mangrove at the coast of Maranhão, in order to determine its reproductive period in the studied mangroves and to compare it with the closed season estabilished by law at Maranhão State. We carried out 12 monthly collections from October 2014 to October 2015 in two mangroves. The first is located in Quebra Pote - São Luís (2º 41,344’ S; 44º 12.604’ W), and the second is located in Araçagi - Raposa (02°27.181' S; 44°09.548' W). Sampling was performed by means of fishing effort, for 1 hour. The specimens were stored in plastic bags and frozen until the analysis time. In laboratory, we conducted biometrics and sex discrimination of each specimen. We then removed the carapace of each specimen with tweezers and scissors in order to macroscopically examine the color, consistency and thickness of the gonads. Four maturation stages were determined: Immature (IM), under development (UD) developed (DE) and exhausted (EX). For the determination of the reproductive period, we monthly performed the registration of female with gonads developed and ovigerous females in all study period. We calculated the sex ratio for each collection month and for the full sampling period. Chi-square test (χ2) was performed to verify differences on sex ratio, at the 0.05 significance level. The size at first gonadal maturation was calculated using Statistica software. A total of 399 specimens of U. cordatus was obtained, 253 from Araçagi and 146 from Quebra Pote. The frequency of females in mangrove Araçagi was higher than of males, at which the absolute abundance of 133 females to 120 males. However, in Quebra Pote mangrove was observed abundance of 89 males to 57 females. The crabs population of Araçagi proved to be more equilibrated, with the male/ female ratio of 1: 1.10, no statistical differences between the sex ratio of the organisms analyzed (χ2 = 0.66). Unlike observed in Quebra Pote, which has submitted a male/ female ratio of 1.7: 1, showing statistical differences between sex ratios with a predominance of males (χ2 = 9.70). The analysis of each month sampling in Araçagi mangrove registered a significant predominance of females in October (χ2 = 5), while in Quabra Pote predominated males in January (χ2 = 12.46) and March (χ2 = 20.56). In relation the maturation of the analyzed specimens, we observed that 21.1% of the analyzed females had developed gonads in Quebra Pote mangrove, whereas developed males represented 39.3%. In Araçagi, 13.5% of females exhibited developed gonads and 16.7% of males. In both mangrove, the size of mature males was lower than in females. In Araçagi, the carapace of mature specimens exhibited 44.55 mm wide in females and 37.40 mm wide in males. Whereas in Quebra Pote, the mature females showed carapace of 46.66 mm and mature males exhibited carapace with minimum wide of 42.49 mm. The average size of first maturation is a very important estimate on reproductive biology studies, especially to commercial species, because it provides benefits for conservation plans such as the minimum size of commercial catch. In the study mangroves, differences in the reproductive period of U. cordatus were not observed, once suitable females for reproduction occurred among the months of December to April, with reproductive peak in the months of December to March. The ovigerous females were registered only in January, February and March. We also observed reproductive migration of crabs for the copulation in January. These results revealed that the reproduction of the “uçá”-crab may be classified as seasonal, occurring between the months of December to April, since females with developed gonads and ovigerous females were observed only at this time. Our results suggest that the reproductive period of “uçá”-crab is more extensive than the period established by the Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis (IBAMA) for the State of Maranhão, period covering some days of January, February and March. In this sense, the present study was highly relevant due to indicating primordial aspects to crab fisheries management, once the crabs are resources of social and economic importance in the coast of Maranhão.
Keywords:
Reproductive period,
“Uçá”-crab,
Reproductive biology,
Maranhão mangroves,
Ucides cordatus
Conference:
XIX Iberian Symposium on Marine Biology Studies, Porto, Portugal, 5 Sep - 9 Sep, 2016.
Presentation Type:
Poster Presentation
Topic:
4. FISHERIES, AQUACULTURE AND BIOTECHNOLOGY
Citation:
Almeida
ZS,
Sousa
DB,
Tchaicka
L,
Fortes
RN,
Araujo
A and
Ribeiro
RP
(2016). Reproductive period and size at first maturity of Ucides cordatus Linnaesus, 1763 (Crustacea: Decapoda) in two mangrove of Maranhão, Brazil
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Front. Mar. Sci.
Conference Abstract:
XIX Iberian Symposium on Marine Biology Studies.
doi: 10.3389/conf.FMARS.2016.05.00127
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Received:
30 Apr 2016;
Published Online:
03 Sep 2016.
*
Correspondence:
Dr. Zafira S Almeida, State University of Maranhão, Chemistry and biology, São Luis, Maranhão, Brazil, zafiraalmeida@hotmail.com