Sexual maturity, reproductive cycles, and juvenile recruitment of Perisesarma Guttatum (Brachyura, Sesarmidae) at Ponta Rasa mangrove swamp, Inhaca island, Mozambique

  • Flores A
  • Saraiva J
  • Paula J
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Abstract

The sesarmid Perisarma guttatum is the most abundant crab species inhabiting the lower man- grove areas at Inhaca Island, and presumably an ecologically important species in this habitat. Among the scarce available information on its population ecology, this species is known to follow a semi- lunar rhythm of larval release, with breeding probably extended year-round. In this study, a popula- tion of P. guttatum was examined, from which estimates of sexual maturity were carried out for both sexes, and breeding activity was monitored to describe short-term variation of reproductive in- tensity. In an attempt to relate reproductive cycles with recruitment patterns of young, a systematic random sampling design was used to quantify and describe the juvenile population. Reproductive parameters in adults and density estimates for juveniles were obtained from samples taken at 4-d in- tervals over a 3-mo period. Reproductive activity increased over the study period. Females released larvae around the new and full moon, but lunar variation of the ovigerous ratio with peaks preced- ing full moon periods indicated that different breeding groups may account unevenly for the repro- ductive output of the population. Very young recruits made up the larger fraction of the juvenile popu- lation, and their density increased from the beginning to the end of the sampling season. Density variation pattern of first-crab stages followed fortnight cycles, but slow growth prevented recruit- ment pulses to be tracked in size-frequency distributions. Polymodal distributions corresponded to recent recruits and older juveniles originating from previous settlement seasons. Growth rates of iden- tified age groups suggest that sexual maturity in females is likely to be achieved after 2 years or more

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Authors

  • a a V Flores

  • J Saraiva

  • J Paula

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