Ambariyanto, R.Hartati, Widianingsih

Source: SEAMEO BIOTROP's Research Grant | 2021


Stichopus hermannii or gamat sea cucumber is an economically important species of sea cucumber, the demand is high, so the fishing effort becomes excessive. This condition will decrease their stock population. One good way to deal with the depleted stock is by sea ranching. The aim of this study was to conduct community-based sea ranching of S. herrmanni in the Nyamuk Island, in the Karimunjawa National Park, Jepara. Nine sea pens measuring 5x5x1.5 meters were installed and 30 individual sea cucumbers were stocked per sea pen with lengths ranging from 9.9-19.0 cm (average 14.95 cm) and weight ranged from

45.0   to 139.07 grams (with an average weight of 137.34 grams). Sea pens are installed at locations of 50, 100, and 150 meters from the beach. Length and weight measurements as well as the number of living individuals of ranched sea cucumber are carried out every month. Ranched for 3 months, the sea cucumbers showed a slight difference between sea pen locations. Sea cucumbers reared in sea pens located close to the mainland had a higher absolute growth (13.3 cm and 87.89 grams) and growth rate of 0.71 and 0.55%/day in length and weight compared to other locations. Sea cucumbers that are kept in an open location with the open sea have the lowest length and weight. It also showed   that sea pens close to the coast have the highest survival (71%) compared to other sea pens. The water quality (temperature, salinity, dissolved oxygen is 28.5-29.5oC, 30.2-30.6 ppt, and 7.2-8 ppm, respectively) during sea ranching is very good and supports the life of sea cucumbers. The impact of sea ranching S. herrmanni on the sediment was also observed, namely by measuring changes in nitrate and phosphate in the sediment. In sea pens 1, 2, and 3, the nitrate concentration increased from the beginning to the end of the study, as did the phosphate concentration. Nitrate and phosphate levels indirectly affect the growth of seagrass and microphytobenthic, which is the food for sea cucumbers. Sediment changes are also seen in the particle size character of the sediment, where the amount (%) of gravel decreases in the three sea pens, the coarse sand varies slightly in sea pens 2 and 3, but in general the levels decrease. There was an increase in fine sand in the three sea pens. Meanwhile, the silt content decreased. Chlorophyll-a concentration; Chlorophyll-b, chlorophyll-c, total carotene and phaeophytine in sediment (mg/g) of sea pen ranching S. herrmanni at the end of rearing were reduced compared to the beginning of stocking, while the control was not much different. This is related to the nature of sea cucumbers as bioturbators, which melt food by stirring the sediment around it. Through this community-based sea ranching activity, the fishermen group "Maju Lancar" and Karang Trauna "Bintang Muda" are able to cultivate sea cucumbers which can be a productive activity.


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