Reproductive biology of the orange mud crab Scylla olivacea (Herbst, 1796) from the Pichavaram mangroves of south-east India

Abstract

The present study was conducted to assess the size distribution, sex ratio, size at first sexual maturity, fecundity and spawning season of the commercially important orange mud crab Scylla olivacea (Herbst, 1796) in Pichavaram mangroves in south-east India. This study is the first contribution to the knowledge of reproductive biology of S. olivacea from the Indian coast. Size distribution analysis in the fishery revealed the irrational exploitation of undersized S. olivacea. The estimated sex ratio deviated from equality, being 1:0.87, revealing a male domination. Size at first sexual maturity was determined to be 87 mm in carapace width (CW) in females. Fecundity ranged from 1.16 to 3.53 million in females of 76 to 135 mm CW. Breeding takes place year-round with a peak in pre-monsoon, indicating that it is a prolific breeder. Results revealed that immature individuals of S. olivacea contributed significantly to the catches and thus an effective management of the resource by framing minimum legal size is crucial so that the females are allowed to spawn at least once prior to capture.

Population parameters of the orange mud crab Scylla olivacea (Herbst, 1796) from the Sundarban mangrove forest in Bangladesh

“…Recruitment of both sexes exhibited a bimodal recruitment pattern where young crabs are added to the population continuously throughout the year in the study area with a major recruitment peak for males from November to January and for females from February to April ( Figure 6 ). Similarly, Viswanathan et al (2019) reported major recruitment of S. olivacea from December to March in Pichavaram mangrove, India. They also reported that larval development and succession of juveniles take place within 3–4 months after breeding.…”

“…The smallest CW of this mud crab recruitment occurs at 35mm, 45mm, and 47mm CW in Philippine, India, and Malaysia respectively ( Viswanathan et al, 2019 ; Waiho et al, 2016 ; Walton et al, 2006 ). The largest CW of male crab in this study was 164 mm (mean 102.05 ± 24.5 mm) whereas the CW was 148 mm (mean 104.33 ± 77.4 mm) in India ( Viswanathan et al, 2019 ) and 134 mm CW (mean 90.4 ± 12.66 mm) in Malaysia ( Waiho et al, 2016 ). The CW of S. olivacea caught from Sundarban was quite high; nevertheless, the mean value is comparatively low.…”

“…The overall recorded male and female ratio in present study was 1:0.66 and evinced the existence of male domination over female in the population. The male and female sex ratio was 1:0.87 in the Pichavaram mangroves of India ( Viswanathan et al, 2019 ) and 1:0.77 in Malaysian mangrove swamp ( Jirapunpipat, 2008 ). Relatively lower percentage of female especially in sub-adult population class size ( Figure 8 ) is found in the study areas.…”

“…The CW ∝ of same species in other Asian countries including India and Malaysia are similar. The CW ∝ of male and female S. olivacea were 148.05 mm and 138.8 mm, respectively in Pichavaram mangroves India ( Viswanathan et al, 2018 ). Similarly, the CW ∝ of common S. olivacea was 154.82 mm in Setiu wetland areas, Malaysia ( Zaidi et al, 2011 ).…”

Fishing pattern and environmentally friendly analysis on mud crab (Scylla spp.) fishery in Mojo mangrove ecosystem, Pemalang Regency, Central Java, Indonesia

“…In Figure 1 shows that anthropogenic pressure on mud crabs in the Mojo mangrove ecosystem increases during the west monsoon season (rainy season), it is caused during the rainy season the mud crabs make a reproductive phase [18,19,20]. Differences in peak reproductive seasons may be related to the suitability of the environmental conditions of the waters in supporting the reproduction process.…”