Species composition, reproduction, and body size of mud crabs, Scylla spp., caught in Urado Bay, Japan

Ogawa, Cynthia Yuri; Hamasaki, Katsuyuki; Dan, Shigeki; Obata, Yasuhiro; Kitada, Shuichi

doi:10.1163/193724012x649787

Cited by 23 publications

(17 citation statements)

References 20 publications

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“…The largest crab caught during this study was 147 mm and this was larger than reported in Thailand (135 mm) and smaller than reported in Malaysia (153 mm) (Moser et al, 2005;Walton et al, 2006;Ikhwanuddin et al, 2011). The size range observed in the Urado Bay, Japan was between 70 and 140 mm (Ogawa et al, 2012) and this again was comparable with the maximum size observed in the present study. In Thailand, Hamasaki et al (2011) observed size ranges between 86 and 129 mm.…”

Section: Discussionsupporting

confidence: 83%

“…The key morphological characters of S. olivacea includes red to brown coloured carapace, low rounded frontal spines, single reduced spine in the carpus of the chelipeds and absence of obvious polygonal markings in the legs and abdomen (Keenan et al, 1998). Investigations on reproductive biology of S. olivacea are limited and have been done on the populations in Thailand (Tongdee et al, 2001;Overton and Macintosh, 2002;Koolkalya et al, 2006;Hamasaki et al, 2011), Malaysia (Ikhwanuddin et al, 2011;Waiho et al, 2016) and Japan (Ogawa et al, 2011;Ogawa et al, 2012). However, such works from Indian waters are not available.…”

Section: Introductionmentioning

confidence: 99%

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

Viswanathan¹,

Pravinkumar²,

Suresh³

et al. 2019

Indian J. Fish.

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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.

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Section: Discussionsupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

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

Viswanathan¹,

Pravinkumar²,

Suresh³

et al. 2019

Indian J. Fish.

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“…Apart from morphological variations, variation in body size is also obvious among Scylla species. S. serrata is the largest, followed by S. tranquebarica and S. paramamosain (Ogawa et al, 2012;Fazhan et al, 2017a). S. olivacea is considered as the smallest among the four species (Waiho, Fazhan & Ikhwanuddin, 2016b;Fazhan et al, 2017a).…”

Section: Introductionmentioning

confidence: 99%

Morphological descriptions and morphometric discriminant function analysis reveal an additional four groups of Scylla spp

Fazhan

Waiho

Quinitio

et al. 2020

PeerJ

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There are four species of mud crabs within the genus Scylla, and most of them live sympatrically in the equatorial region. Apart from a report in Japan about the finding of a natural Scylla hybrid more than a decade ago after the division of genus Scylla into four species by Keenan, Davie & Mann (1998), no subsequent sighting was found. Thus, this study investigates the possible natural occurrence of potential hybridization among Scylla species in the wild. A total of 76,211 individuals from mud crab landing sites around the Malacca Straits, South China Sea and Sulu Sea were screened. In addition to the four-purebred species, four groups (SH 1, n = 2, 627; SH 2, n = 136; SH 3, n = 1; SH 4, n = 2) with intermediate characteristics were found, mostly at Sulu Sea. Discriminant Function Analysis revealed that all Scylla species, including SH 1 - 4, are distinguishable via their morphometric ratios. The most powerful discriminant ratios for each character and the top five discriminant ratios of males and females were suggested. The carapace width of SH 1 males and females were significantly smaller than pure species. Based on the discriminant ratios and the description of morphological characters, we hypothesize that the additional four groups of Scylla with intermediate characteristics could be presumed hybrids. Future work at the molecular level is urgently needed to validate this postulate.

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“…These assumptions are unlikely to be valid for a number of reasons, including (1) differential growth between sexes, with males growing faster than females (Sara ); (2) a skewed sex ratio in the annual catch (which is typically dominated by males; Sara ; Ogawa et al. , ; Dumas et al. ); (3) differences in the MLS applied to each sex; and (4) potential variation in mortality rates between sexes (Ward et al.…”

Section: Discussionmentioning

confidence: 99%

“…As sex-specific catches are not reported by mud crab fishers in the NT, males and females were assumed to contribute equally to the historical catch and form equal parts of the modeled biomass estimates. These assumptions are unlikely to be valid for a number of reasons, including (1) differential growth between sexes, with males growing faster than females (Sara 2010); (2) a skewed sex ratio in the annual catch (which is typically dominated by males; Sara 2010; Ogawa et al 2011Ogawa et al , 2012Dumas et al 2012); (3) differences in the MLS applied to each sex; and (4) potential variation in mortality rates between sexes (Ward et al 2008;Sara 2010;.…”

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confidence: 99%

Simple Modeling to Inform Harvest Strategy Policy for a Data‐Moderate Crab Fishery

et al. 2019

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Attempts to model the giant mud crab Scylla serrata fishery in the Northern Territory (Australia), have often been complex and the results difficult to interpret, leading to divergent estimates of fishing mortality. This has hindered the development of meaningful management policy. Additionally, analyses based on the entire Northern Territory fishery have masked the extreme variation in catches observed along the Gulf of Carpentaria coast. We applied a structurally simple model to visualize the historical patterns in stock size, recruitment, fishing mortality, and fishing mortality at maximum sustainable yield in the western Gulf of Carpentaria mud crab fishery (WGOCMCF) from 1983 to 2017. We also projected future catch and female spawning stock biomass (FSSB) under positive, neutral, and negative recruitment scenarios for three closure periods contained in the fishery harvest strategy (which start in October, if triggered) and compared these with the results of equivalent closures beginning in September. This exercise was undertaken because of known and significant changes in the proportion of fishing effort across different months as well as large variations in the proportion of females harvested each month (with both factors being particularly low in December). These differences were annualized and incorporated into the yearly time step of the model. Predicted catch and FSSB were similar for shorter closure periods (3 or 6 weeks), irrespective of the starting month. However, initiating a 3‐month closure in September rather than October could lead to a 16–17% increase in FSSB under negative and average recruitment anomalies, imposing a 9–10% reduction in predicted catch. Based on our experience applying a simple model to the WGOCMCF, we also describe processes and practices that could improve the quality of assessment data for this and other data‐moderate crab fisheries.

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Species composition, reproduction, and body size of mud crabs, Scylla spp., caught in Urado Bay, Japan

Cited by 23 publications

References 20 publications

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

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

Morphological descriptions and morphometric discriminant function analysis reveal an additional four groups of Scylla spp

Simple Modeling to Inform Harvest Strategy Policy for a Data‐Moderate Crab Fishery

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