One aspect of a sustainable aquaculture system is the security of feeding material supply (Fatchiya, 2015). In several informal discussions during the survey, three traditional techniques in shrimp feeding were revealed. These were the klekap method; the Lumut method, and growing plankton. While not directly related to the mud volcano, these techniques are a form of human capital that has become widespread in Sidoarjo.
In the semi-intensive ponds, farmers add artificial feed to increase farm production.
At this level, the feed provided is supplementary. Typically, this feed stuff comprises materials easily obtained around the pond at a cheap price. To grow natural food in the pond, farmers observe what kind of natural foods is being eaten by fish or shrimp or shrimp fry spawning in their plots. Examples of suitable natural food are klekap and plankton that could be used separately or as a mixture together.
Klekap method 4.4.5.1
The klekap method was explained by male respondent 6 and male respondent 7 who represent farmers working with PT ATINA in cultivating eco shrimp in Buduran sub district and by male informant 2, one of the role models for tiger shrimp cultivation in Sidoarjo.
Klekap is an algae that consists of Oscillatoria, Phormidium, Lyngbya, Spirulina, Diatomae (Navicula, Nitzschia, Amphora, Pleurosigma), Protozoa (Zoothamnium, Vorticella, Epistylis, Acineta), bacteria, Rotifera and worms. Klekap is able to grow on the walls and bottoms of the ponds. The algae that grow have chlorophyll that enables the process of photosynthesis.
115 According to male respondents 6, 7, and 2, the process of making Klekap takes from 7 to 15 days. While waiting for the Klekap to grow in the bottom of the pond and then become compacted, the farmer also makes improvements in the infrastructure of the ponds. These improvements include strengthening pond embankments, and cleaning and repairing the irrigation channel that is located inside the pond. Some farmers call this caren.
The water gate and drainage maintenance process are conducted by clearing the ponds of mangrove roots that spread inside the ponds. After finishing the drying and compacting process, the next step is to add organic fertilizer. The quantities of organic fertilizer needed depends on the soil fertility level. According to male respondent 2, the organic fertilizer composition consists of chaff, ground coconut, cattle manure (cow, buffalo or goat) or guano (bat manure).
After fertilizing, the next process is a wetting process. The wetting process is started by filling with seawater to a height of 3-10 cm. The seawater enters, then evaporates under the sun until around 20 percent dry. This process aims to neutralize organic materials in the fertilizer.
After the drying process, the next stage is adding urea50 and TSP51. Before adding the urea and TSP, the pond is watered to a height of 10-15 cm for 50 kg per hectare per pond. However, for ponds that contain a lot of mud the ratio of urea and TSP is 2:1.
After this stage, farmers fill the pond with sea water up to the adequate level for fish and shrimp. The last stage is preparing the shrimp fries and the fish seed to be cultivated in the pond.
50 Urea is a chemical fertilizer containing high levels of Nitrogen (N). Nitrogen is an essential nutrient for plants. Urea is an organic compound composed of elements of carbon, hydrogen, oxygen and nitrogen by the formula CON2H4 or (NH2) 2CO. Urea is also known by the name carbamide or diaminomethanal.
51 TSP is Triple Super Phosphate Fertilizer. This fertilizer (TSP) is an inorganic nutrient used to improve soil nutrients for agriculture. TSP chemical formula is Ca(H2PO4). This fertilizer contains P2O5 (Phosphate) about 44-46%.
116 Lumut method
4.4.5.2
Lumut method is a method of growing mould for shrimp feed. Most key respondents mentioned this method when discussing traditional shrimp feeding. It involves trough grown fungus used as a natural feed for shrimps.
The first step in the preparation of this method is drying moss from the bottom of the pond, which takes about three days in the sun. Male respondent 6 explained that the use of the sun shining on the bottom of the pond is to create a humid environment for growing moss. Subsequently, dried soil is planted with green moss evenly over the surface (yard plot), and water is added to approximately 20 cm deep.
After 3-7 days of watering the pond, the next step is adding fertilizer such as urea and TSP. The urea is used at 48 grams per cubic meter of water and TSP at 20 grams per cubic meter of water. A week after the last treatment, the pond is watered up to 40 cm height. In this state the moss grows and is ready to be the food supply of the shrimp.
Growing plankton 4.4.5.3
The plankton growing method was explained by male respondent 2 while the researcher followed him in his activities in maintaining his pond. Growing plankton is quite different from the previous two methods. In the earlier explanation of growing plankton, male respondent 2 stated that precise measurement both in watering and fertilizer composition is a significant factor. He argued that plankton requires adequate water and an accurate combination of nitrogen (N) and phosphorus (P).
In detail he explained the four steps of growing plankton. First is a drying process, which takes from 3-5 days. Second is watering up to a height of 70-100 cm. The water can be sea water or water from a reservoir pond. Third is adding fertilizer (urea and TSP), per cubic meter of water, ideally is needed 2,065 gram urea, and 1,097 grams TSP. Both fertilizers are mixed evenly, then placed on a table which is specially designed, and submerged 15 -20 cm below the surface of the water. This table is made of bamboo poles with a plate or board. The size of the table is 0.85 x
117 0.85m for one hectare. The table is mounted on the edge of the pond following the wind direction. Fertilizers dissolve slowly and spread over the pond through water movement.
The last step is evaluating the density of the plankton through use of a water clarity test. Water that has more phytoplankton is greener than the water with less phytoplankton. This test uses a Secchi disk. Put the Secchi disk at 30 cm depth, once the Secchi disk is not visible this means the density of the phytoplankton is high and needs to be reduced by removing some of the water and adding new water. However, if the Secchi disk is visible and the water volume remains stable, it means that the ponds need more fertilizer.