Source: SEAMEO BIOTROP's Research Grant | 2021
Abstract:
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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