Food and Feeding Habits of the Mud Crab, Scylla serrata Forskal Inhabiting the Negombo Lagoon in the West Coast of Sri Lanka
TL;DR: It became evident that the crabs feed continuously during the night and only at the high tide in the daytime, and there is no seasonal variation in the food items.
Abstract: The Mud crab, Scylla serrata is an economically important crustaceaninhabiting the lagoons of the west coast of Sri Lanka Currently there is interestin mass rearing of the species in ponds Thus, a study was carried out to identifythe food and feeding habits of Seylla serrata in the Negombo Lagoon Thestomach contents of crabs of different sizes caught by unbaited gears were screenedto identify the food constituents and it wasfound that crabs of medium size (subadults)mainly fed on molluscs and the small ones (juveniles) on crustaceansMonthly samples were also studied and found that there is no seasonal variationin the food items Diurnal studies were carried out to determine the feeding timeand it became evident that the crabs feed continuously during the night andonly at the high tide in the daytime
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TL;DR: The study suggests that replanting of mangroves even in mono-genus stands was effective in restoring mud crab populations, indicating recovery of an ecological function to a level equivalent to that of natural mangrove environments.
63 citations
TL;DR: It is concluded that full domestication of tropical Indo-West Pacific Portunidae will not occur in the next 5 to 10 years and that the main constraints to be overcome are the aggressive behavior of the crabs, their carnivorous diet and competition for suitable coastal farm sites.
Abstract: Large and long-term investments in research, development and technology verification are required for the successful culture, domestication and coastal stock enhancement of any species, including crabs. As more species options are sought for culture, the choice of candidate species could be guided by ex-ante assessments to help identify suitable species and anticipate future constraints and opportunities. Focusing on tropical Indo-West Pacific Portunidae, we propose multiple criteria for domestication and stock enhancement that include life cycle, diet and feed conversion efficiency, behavior, disease resistance, growth rate, marketability, farming systems, profitability and environmental impact. The chief candidate species (four species of Scylla, Portunus pelagicus, P. sanguinolentus, and Charybdis feriatus) are considered against the criteria. Experience in the stock enhancement of P. trituberculatus, a subtropical portunid, is reviewed. We conclude that full domestication will not occur in the next 5 to 10 years and that the main constraints to be overcome are the aggressive behavior of the crabs, their carnivorous diet and competition for suitable coastal farm sites. We also recommend considering the tropical Portunus and Charybdis species examined here as additional or alternative options to the Scylla species. Stock enhancement may be feasible in some locations, provided suitable fisheries management and industry institutions are created.
62 citations
TL;DR: Type of lipid class and fatty acid components in mature ovaries as well as in NSE are generally considered to be indicative of their importance in reproductive physiology and embryonic and larval development.
Abstract: Wild-caught and pond-reared female mud crab Scylla serrata at different stages of ovarian maturation were collected from Samar and Capiz, Philippines. Crabs were categorized into five stages according to the external morphological and microscopic appearance of the most advanced oocytes. The ovaries, hepatopancreas, muscle and newly spawned eggs (NSE) were analysed for lipid class components and fatty acids. Total lipid was higher in pond-reared than in wild-caught crabs but increased with ovarian maturation in both groups. Ovarian lipid peaked at the fully mature stage, coinciding with a decline in hepatopancreatic and muscle lipids. Lipid levels declined significantly in spent females. The tissues contained elevated highly unsaturated fatty acids such as arachidonic (20:4n-6), eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acids, but at higher levels in late maturing and fully mature ovaries and in NSE. The type of lipid class and fatty acid components in mature ovaries as well as in NSE are generally considered to be indicative of their importance in reproductive physiology and embryonic and larval development.
45 citations
TL;DR: This work describes the profile of five proteases and four carbohydrases from the crustacean decapods Macrobrachium australiense, Scylla serrata, P. pelagicus and P. esculentus feeding in the natural habitat, to provide an indication of their digestive capabilities.
Abstract: This work describes the profile of five proteases and four carbohydrases from the crustacean decapods Macrobrachium australiense (Holthuis), Scylla serrata (Forskal), Portunus pelagicus (Linnaeus), Penaeus esculentus, Penaeus plebejus (Hess) and Metapenaeus bennettae (Racck & Dall), feeding in the natural habitat, in order to provide an indication of their digestive capabilities. The results raised the following points. First, species from each family showed a particular suite of digestive enzymes. Second, the activity of cellulase from M. australiensis and S. serrata, using AZCL-HE cellulose as the substrate, was around 90% higher than that observed with AZO-CM cellulose. However, for P. pelagicus and P. esculentus, the enzyme activity was better with AZO-CM cellulose. Third, M. australiense displayed the highest ratio of amylase to protease activity. In contrast, Portunidae species, P. pelagicus and S. serrata showed the lowest ratios. Fourth, comparison of the laminarinase activity of M. bennettae and P. esculentus in October (Spring) and December (early Summer) showed a significant decrease in December. Finally, the wide distribution of digestive enzymes in these crustaceans may reflect different feeding habits and habitats.
43 citations
TL;DR: Growth rate and survival of mud crabs cultured in individual drive-in cages located in the mangrove forests dominated by Rhizophora mucronata were evaluated and it was revealed that crabs fed with mixed feed had significantly higher % growth compared to fish offal but were similar to gastropod meat.
Abstract: The populations in coastal areas in east Africa have increased dramatically in the last decades, resulting in increased pressure on coastal resources. The examples are declining fish catches, deteriorating conditions of coral reefs and reduction of mangroves forests. The objective of the study was to asses the potential of grow-out Aquac of mud crabs Scylla serrata, as an alternative livelihood for resource-poor coastal communities. Growth rate and survival of mud crabs (S. serrata) cultured in individual drive-in cages (30 x 30 x 30 cm) located in the mangrove forests dominated by Rhizophora mucronata were evaluated. The effect of feed (Terebralia pallustris - gastropod meat, fish offal and mixture of the 2) was determined in a completely randomised design. Feeding was done at 10% body weight at incoming tide throughout the experimental period of 120 days. Monthly sampling was employed and total weight (g), cheliped length (cm), carapace length (cm) and width (cm) were measured. The study aimed at establishing the growth rate, moulting and mortality of crabs fed using locally available feeds. A total of 180 drive-in cages were used for the experiment giving 60 replicates for each treatment. Drive-in cages were built with "fitos" and grouped in sets of 10 for easy management. Crab seed stock of 50 - 380 g for the experiment were bought from artisanal fishermen application of ANOVA and post-hoc test revealed that crabs fed with mixed feed had significantly higher % growth (47.9%) compared to fish offal (33.4%) but were similar to gastropod meat (43.2%) p < 0.05. Growth rate was significantly affected by feed type, where higher values were recorded in mixed feed diets (gastropod meat and fish offal, 1.29 g/day) compared to the individual feeds (0.96 and 0.97 g/day for fish offal and gastropods meat respectively. There was no significant difference in growth of monosex crabs female (0.996 - 1.55 g/day) and males (0.893 -1.01 g/day) p = 0.373.
Key words: Mangrove, mud crab, feed, drive-in cage, growth.
32 citations
Cites result from "Food and Feeding Habits of the Mud ..."
...Though it has been observed from studies that the juvenile S. serrata show a preference for detritus, while much larger crabs have more crustacean and fish in their diet (Prasad and Neelakantan, 1988) but no information exists on the nutritional requirements for bigger crabs cul- 008 J. Ecol....
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TL;DR: The natural diet, rate of foregut clearance and diurnal activity of the crab Scylla Serrata were determined, and it was concluded that S. serrata does not normally catch mobile forms such as fish and penaeid prawns.
Abstract: The natural diet, rate of foregut clearance and diurnal activity of the crab Scylla serrata were determined The gut volume is related to size of crab as gut volume (ml)=007e0033x, where x=carapace width in millimetres Fifty per cent of crabs collected in Australia and South Africa contained molluscan remains and about 21% contained crustacean remains — chiefly grapsid crabs Fish remains were rarely found, and it was concluded that S serrata does not normally catch mobile forms such as fish and penaeid prawns Gut clearance of organic tissue was rapid and almost complete after 12 h Fish bone was retained for a mean time of 2 to 3 days, and shell for 5 to 6 days Time-lapse photography, using infra-red light, was used to record activity Visible light flashes reduced activity S serrata remained buried during the day, emerging at sunset to spend the night feeding, which occurred intermittently even when unlimited food was available If no food was present the amount of time spent on the substrate surface was halved
213 citations
TL;DR: Scylla serrata in a South African estuary occurred more frequently in that part which had the highest number of prey organisms, and showed a preference for small crabs as prey.
Abstract: Scylla serrata in a South African estuary occurred more frequently in that part which had the highest number of prey organisms. Food location was by contact chemoreception, using the dactyls of the walking legs. Major prey groups were burrowing bivalves, attached bivalves and small crabs. s. serrata showed a preference for small crabs as prey. Because of their larger mass and higher energy content compared with other prey organisms, these crabs represented the major energy source of S. serrata in this area.
68 citations
TL;DR: The St Lucia system is a South African estuarine lagoon which experiences wide salinity fluctuations; recent records show a range of 2%0 to 89%0; the death of these food organisms during periods of extreme salinity may reduce the carrying capacity of the system for crabs.
Abstract: Summary The St Lucia system is a South African estuarine lagoon which experiences wide salinity fluctuations; recent records show a range of 2%0 to 89%0. The population of the crab Scylla serrata in the St Lucia estuary system was surveyed in January 1977. An estimate based upon catch per unit effort indicated a population of about 180 000 adult crabs. Population density declined with increasing distance from the mouth of the estuary. S. serrata was more abundant in muddy than in sandy areas. The crabs survived a four-month period of low salinity (2%0) in 1976, but their hypersalinity tolerance (60%0) is too low to permit their existing in most of the system during periods of high salinity. S. serrata feeds chiefly on benthic molluscs and crustacea; the death of these food organisms during periods of extreme salinity may reduce the carrying capacity of the system for crabs.
36 citations
TL;DR: Microbenthos and detritus were found to support most of the herbivorous species while larger benthos, emergent halophytes, and plankton play minor roles, and the dominant species were treated in a similar way and reported upon.
Abstract: The food and feeding habits of the influent and subinfluent species (11 fish, 4 shrimps, and 4 crabs) in Hawaiian fish ponds were analyzed to ascertain the biotic interaction. The dominant species were treated in a similar way and reported upon earlier. The ponds are virtually autarchic, and the available food supply is almost totally dependent upon the physical features of the biotope. Microbenthos and detritus were found to support most of the herbivorous species while larger benthos, emergent halophytes, and plankton play minor roles. The animal assemblage within the ponds includes not only herbivores and omnivores but is replete with carnivores, several of which are voracious and reach a large size. Interspecific competition for food and existence is severe. Both mullet and milkfish subsist on microbenthos. Competing also for this source of food are prodigious numbers of poecilids (Mollienesia latipinna and Gambusia affinis) and shrimps which, in turn, form the strongest links in the food cha...
11 citations