Collection of the mud crab Scylla serrata var paramamosain in Tinagong Dagat and Sapian Bay, northern Panay
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Mud crabs were collected by baited traps from the mangroves and estuaries of Tinagong Dagat Bay and Sapian Bay in Capiz, northern Panay monthly over 18 months. Scylla serrata var paramamosain made up 95.4% of the collection and Scylla oceanica, 4.6%. Mean catch rates of S. serrata from Tinagong Dagat was 0.4 crabs/trap in the mangroves and 0.5 crabs/trap in the estuary; in Sapian Bay, 0.9 crabs/trap in both habitats. In both bays, S. serrata occurred year round, but at greater abundance during the rainy season (June–September). Most crabs were 2–10 cm in carapace width, but some were up to 14 cm. Crabs were smaller in the mangroves (modal size 5 cm) than in the estuary (modal size 8 cm). The smallest crabs (2 cm) were collected in the mangroves in January and May, and the 3 cm crabs occurred most months except June, August, September, and November. The presence of smaller crabs in greater numbers in the mangroves indicates affinity for shallow, sediment-laden habitat with plenty of shelters in the form of mangrove roots and leaves. Very few crabs over 8 cm were captured in the mangroves. Crabs of 4–14 cm were captured in the estuaries, the 12–14 cm ones during July–October. The samples at each site formed several size groups every month, and ‗cohorts‘ could be discerned and followed over the next months. It was estimated that the 2–4 cm size group in January–May reached the size of 8–10 cm by October–November. Juvenile mud crabs apparently spent one year in the mangroves or estuaries. There were more males than females (1F:1.2M) in Tinagong Dagat, but the other way around (1M:1.3F) in Sapian Bay. Berried crabs of 14 cm were occasionally caught by filter net in Tinagong Dagat.
Solis, N. B. (2007). Collection of the mud crab Scylla serrata var paramamosain in Tinagong Dagat and Sapian Bay, northern Panay. In T. U. Bagarinao (Ed.), Research Output of the Fisheries Sector Program (Vol. 2. Reports on Fisheries and Aquaculture, pp. 98-99). Quezon City, Philippines: Bureau of Agricultural Research, Department of Agriculture.
PublisherBureau of Agricultural Research, Department of Agriculture
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Conference paperET Quinitio, FD Parado-Estepa, JJ Huervana & MR Burlas - In MRR Romana-Eguia, FD Parado-Estepa, ND Salayo & MJH Lebata-Ramos (Eds.), Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia: Challenges in Responsible Production … International Workshop on Resource Enhancement and Sustainable Aquaculture Practices in Southeast Asia 2014 (RESA), 2015 - Aquaculture Department, Southeast Asian Fisheries Development CenterWidespread interest in mud crab species is increasing because these are highly prized both in domestic and export markets. Among the three mud crab species commonly found in the Philippines, Scylla serrata, S. olivacea, and S. tranquebarica, S. serrata is preferred by farmers because it is larger and less aggressive than the other species. Likewise, S. serrata is the most widely distributed species in the Indo-west Pacific region. Hatchery-produced seedstock are presently used by some crab farmers in their grow-out operations. In the hatchery phase, feeding mud crab larvae with shrimp formulated diets and natural food was found to reduce the occurrence of molt death syndrome, one of the major problems in seed production. Larvae given 25% formulated diet (FD) + 75% natural food (NF; rotifers and Artemia) and 50% FD + 50% NF showed better performance than those larvae fed 100% FD, 100% NF and 75% FD + 25% NF indicating that usage of natural food, especially the expensive Artemia, can be reduced. Since the early crab instar (C) produced in the hatchery need to be grown further before stocking in grow-out ponds, two phases of nursery culture have been developed. C1-2 are grown to 1.5-2.0 cm carapace width (CW) size in the first phase and further grown to 3.0-4.0 cm CW in the second phase. Nursery rearing is done in net cages installed in ponds for easy retrieval. A combination of mussel or trash fish and formulated diet is used as feed. Domestication of the mud crab S. serrata as a prerequisite to selective breeding has been done at SEAFDEC/AQD. Likewise, defining criteria for the determination of quality of newly hatched zoeae for stocking in the hatchery was initiated. Newly hatched zoeae were subjected to starvation and stress test using formalin. Starvation failed to elicit responses that were significantly different between the good and poor quality larvae hence it is not suitable for larval quality evaluation. Based on three-year data, the formalin stress test gave mean cumulative mortalities of 2.38±0.32, 8.24±0.88, 20±1.58 in good quality larvae, and 43.74±2.39 while 22.93±4.19, 63.68±7.17, 84.29±3.88 and 97.65±1.06 for poor quality larvae at 0 (control), 20, 30 and 40 ppm formalin, respectively. As formalin level increased, cumulative larval mortality also increased regardless of the quality of the larvae. Formalin stress test proved to be a reliable method to determine whether a batch of newly hatched zoeae was of good or poor quality.
ArticleMorphological changes in the embryos, egg size and development, incubation period and morphological structures of newly hatched zoea of three mud crab Scylla species were determined. The three species exhibited similar embryonic development composed of 10 stages. The mean egg diameter of Scylla serrata was significantly larger (P<0.05) at the prehatch stage. The mean egg diameters of Scylla tranquebarica and Scylla olivacea were similar (P>0.05). The incubation period was the longest in S. serrata and the shortest in S. olivacea. There was a positive relationship between egg size and larval size, as S. serrata exhibited the largest egg size and first zoea. However, no correlation was detected between egg size at prehatch and lengths of the morphological structures of the newly hatched zoea. The three species exhibited similar lengths of cephalic structures, but S. olivacea had significantly shorter (P<0.05) abdominal structures. The duration of spawning from ablation was the shortest in S. tranquebarica and the longest in S. olivacea. The study is relevant to aquaculture and fisheries management of Scylla species.
Seasonal abundance, distribution and recruitment of mud crabs (Scylla spp.) in replanted mangroves ME Walton, L Le Vay, JH Lebata, J Binas & JH Primavera -
Estuarine, Coastal and Shelf Science, 2006 - ElsevierThe abundance and distribution of mud crabs were studied in a replanted mangrove forest in Buswang, Aklan, Philippines. Two fishing gears, lift nets and bamboo traps, were used to monitor relative abundance of Scylla spp. populations from March 2002 to December 2003 inside the mangrove forest. A third gear, a stakenet set across a creek, was used to monitor crabs migrating out of the mangroves during the ebb tide. Scylla olivacea formed 99.3% and 70.3% of the catch in the mangrove and the stakenet, respectively. The percentage of Scylla tranquebarica increased from <1% in the mangrove catches to 29% in the stakenet. Scylla serrata was present at very low levels in both catches. The lack of modal progression in the size–frequency plots and the year-round catch rate of gravid females suggested that recruitment was constant throughout the year. Even though relative abundance decreased over the study period indicating that the stock is being over-exploited, mud crab production is more than equivalent to that of most natural mangroves.