Consumer Preferences and Willingness to Pay for Mud Crabs in Southeast Asian Countries: A Discrete Choice Experiment

The mud crab (Scylla Serrata) is an economically important species found in the mangroves and estuaries of tropical countries and is a popular seafood product in the coastal areas of Southeast Asian markets. The aim of this study is to identify factors affecting consumer preference of mud crabs, and to understand consumers’ willingness to pay (WTP) for these factors in a Singapore market where imported mud crabs from other Asian countries are sold. The results showed that the country of origin matters to participants, affecting purchasing decisions, and consumers were willing to pay approximately 16.48 SGD (11.49 USD, the average price of four shops: 35.55 USD/kg for one mud crab) more if the mud crabs were from Sri Lanka if compared with Indonesian or Cambodian mud crabs. Moreover, consumers were willing to pay 25.08 SGD (17.48 USD) more if the mud crabs were alive and 13.40 SGD (9.34 USD) less if the mud crabs were frozen compared with fresh, but not alive, mud crabs. Furthermore, consumers’ preference in mud crab was associated with the consumers’ religion. Some groups of consumers preferred female mud crabs with eggs over male mud crabs, while other groups preferred male crabs. The results identified diverse consumer preference of mud crabs and, therefore, could provide new insights that are useful for sustainable consumption of mud crabs in the region.

Study of Growth and Survival of Mud Crab (Scylla serrata, Forskal) with Different Salinity Levels in culture media

The aim of this study to find out the optimal level of salinity for the growth and survival of the mud crab (Scylla serrata). The weight of crab seeds were about 47.65-51.32 grams and the carapace length ranged from 64.35-71.30 mm, then put into 12 tanks (1 m x 1 m x 0.4 m) with a density of 4 crab seed per tank. During the maintenance of this test, mangrove crab was fed with fresh chicken intestines as much as 10% of its body weight per day. Water changes are carried out more than 150% per week. At the beginning of the experiment, each tank was conditioned to the same water salinity in all experimental units, namely 33 ppt. To see the effect of differences in salinity levels on the growth and survival of mud crabs, 4 treatments were made consisting of (A) 33 ppt salt content, (B) 31 ppt salt content, (C). The salt content is 29 ppt, and (D) the salt content is 27 ppt. From the results of this experiment, it is known that a decrease in the salt content of 4 ppt is the best treatment for the growth of mud crabs, but has no effect on the survival value.

The potential use of Octolasmis spp. parasites in mud crabs Scylla spp. as a bioindicator for mercury pollution

Nur I, Aris EA, Yusnaini Y, Beavis S. 2021. The potential use of Octolasmis spp. parasites in mud crabs Scylla spp. as a bioindicator for mercury pollution. Biodiversitas 22: 3764-3772. Artisanal small-scale gold mining and the use of mercury is widespread across Indonesia, often characterized by relatively short-lived gold rushes. In the late and post-mining phases, mercury stored in mine tailings and river beds was transported down catchment, posing risks to ecosystems and human health over much longer time scales. These risks can be under-rated when mercury concentrations in water, sediments, and aquatic species are low enough to meet relevant guideline thresholds. In this study in Southeast Sulawesi, Indonesia, we have investigated the Costraca barnacle, Octolasmis, as a bioindicator of mercury contamination. The presence of Octolasmis parasites in mud crabs, Scylla spp., and the accumulation of mercury (Hg) in the hosts, parasites, and the ambient environment, were analyzed across both dry and wet seasons. Severe infestation of Octolasmis was assessed using prevalence, abundance, and intensity. Hg concentrations were significantly higher in the Octolasmis parasites than in the host tissues, water and sediments. The mean bioconcentration factor (BCF) of Hg equaled 7938.21 from water to parasites, and 28.91 from the host’s gill tissue to the parasites. The results suggest that Octolasmis spp. can be used effectively as a bioindicator in coastal catchments impacted by mercury contamination, even when concentrations of mercury are low in water and river sediments. The study provides the first report of Octolasmis spp. parasitized to mud crabs as a reliable bioindicator of Hg contamination and pollution.

A Review of the Nursery Culture of Mud Crabs, Genus Scylla: Current Progress and Future Directions

The nursery stages of mud crab, genus Scylla, proceed from the megalopa stage to crablet instar stages. We review the definition and several of the key stages in mud crab nursery activities. The practice of the direct stocking of megalopa into ponds is not recommended due to their sensitivity. Instead, nursery rearing is needed to grow-out mud crabs of a larger size before pond stocking. Individual nursery rearing results in a higher survival rate at the expense of growth and a more complicated maintenance process compared with communal rearing. The nursery of mud crabs can be done both indoors or outdoors with adequate shelter and feed required to obtain a good survival percentage and growth performance. Artemia nauplii are still irreplaceable as nursery feed, particularly at the megalopa stage, while the survival rate may be improved if live feed is combined with artificial feed such as microbound diet formulations. Water quality parameters, identical to those proposed in tiger shrimp cultures, can be implemented in mud crab rearing. The transportation of crablets between different locations can be done with or without water. The provision of monosex seeds from mud crab hatcheries is expected to become commonplace, increasing seed price and thus improving the income of farmers. Numerous aspects of a mud crab nursery including nutrition; feeding strategies; understanding their behaviour, i.e., cannibalism; control of environmental factors and practical rearing techniques still need further improvement.