Indonesian shrimp farmers are turning to polyculture to increase their profits
Increasing aquaculture productivity does not always depend on the introduction of sophisticated technology or massive investment, as demonstrated by a group of farmers in Pinrang South Sulawesi in their innovative co-culture of king prawns and barramundi.
Although polyculture systems are widespread in Indonesia, this example is unique in that it only arose by accident – after a traditional tiger prawn farmer named Abdul Waris Mawardi found barramundi in his Monodon pond. The fish must have entered the seawater inlet as juveniles and then grown alongside the shrimp as the cycle progressed.
Barramundi tend to become predatory when they appear in traditional brackish ponds, decimating farmers’ target stocks of king prawns and milkfish. However, on several occasions, Mawardi found that barramundi can grow and be harvested along with the crustaceans without impacting shrimp productivity. He therefore thought that the system could increase his productivity if properly managed.
Farmers have found that barramundi can be co-cultivated with shrimp if managed properly
Advantages of Polyculture
Both Monodon and Barramundi are high value species. Traditionally produced shrimp in Pinrang are branded as organic shrimp and sold to the Japanese market through PT. Atina (Alter Trade Indonesia). Farm gate price for Monodon in Pinrang ranges from IDR 59,000 – 115,000 per kg (€3.61 – €7.03 per kg) depending on size at harvest. Barramundi are now mainly sold locally, at a farm-gate price for 250 grams of fish between IDR 30,000 and 50,000 per kg (€1.83 to €3.06 per kg).
Aside from fetching a good price, Barramundi are well suited for polyculture with Monodon as they reach market size in about 3-4 months and are tolerant of a range of water qualities and growing systems.
Mawardi, the coordinator of Pokdakan (farmer group) Cempae-Pinrang, has been developing polycultures of king prawns and barramundi in ponds for three years. Before cultivating barramundi as a second species in polyculture, Mawardi and other farmers produced king prawns and milkfish.
Mawardi developed the polyculture method over three years
However, he says that the productivity of tiger shrimp in terms of survival rate and size is higher when cultured with barramundi. This is because barramundi can eat other wild fish found in the ponds — including tarpon (Megalops cyprinoides), tilapia (Oreochromis mossambicus), and payus (Elops hawaiensis).
To ensure an optimal harvest, several things need to be considered – including pond preparation, seed quality and size, density of each species, and feed management.
Mawardi explains that pond preparation is actually similar to other traditional polyculture systems. The main ingredients are the drainage of ponds; the removal of pests with saponins; the use of organic fertilizers composed of C-organic Fe, Mn and Zn to grow the natural forage for the cultivated species; and liming to ensure soil pH is between 6 and 7.
Phronima’s presence can be clearly seen by observing the bottom of the pond near the embankment. When producers examine a handful of soil from the bottom of the pond, phronima look like mosquito larvae.
Ponds are ready for stock when natural food appears in the form of Phronima sp and plankton. Phronima’s presence can be clearly seen by observing the bottom of the pond near the embankment. When producers examine a handful of soil from the bottom of the pond, phronima look like mosquito larvae. On the other hand, the presence of plankton can be recognized by the greenish-brown color of the water.
Seed stocking plays a very important role in tiger shrimp and barramundi polyculture and determines the ultimate success of cultivation.
To avoid becoming a victim of barramundi, larger king prawns – around 5-8 cm – need to be stored. Farmers are recommended to buy PL 12 from the hatchery and then raise them in the nursery pond for 15 days, or buy larger seed directly from the nursery farmers. Some farmers in Pinrang South Sulawesi have specialized in producing this larger seed.
For every hectare of pond, farmers typically keep 88,000 king prawns and then breed them for about 120 days. Mawardi and his group divided this assembly process into three phases. In the first phase, farmers store 35,000 seeds. The second will be carried out 30 days later with another 20,000. And the last phase is carried out 60 days after the first stocking and includes 33,000 seeds. In the meantime, 3,500 young Barramundi are stocked about 90 days after the first stocking.
Seed stocking plays a key role in the ultimate success of this polyculture method
Like tiger shrimp, the barramundi are stored in a larger size (5-10 cm). Naturally occurring hatchlings are typically 2-4 cm in size and therefore need to be reared in a rearing pond until they reach the desired size.
In this polyculture system, barramundi are fed only waste fish or tilapia babies. Tiger shrimp are now completely dependent on natural food in the form of Phronima sp, aquatic plants and other microorganisms and can therefore be labeled as organic.
Barramundi will not typically eat fresh food in the early stocking phase as their natural behavior is to eat live fish, but they can be trained to eat fresh food. Farmers can do this gradually until the barramundi become accustomed, which takes about a month. Mawardi recommends feeding the barramundi once in the morning and once in the afternoon at a fixed spot by the pond.
Like gradual storage, harvesting is done in phases. The first harvest takes place 60 days after the first stocking and then twice a month at high tide. The harvesting process is carried out with net traps (bagang-bagang) with a mesh size of 5 cm. This allows the later used smaller shrimp to remain in the pond. In the meantime, any barramundi caught should be released and harvested at the end of the growing season.
With these husbandry and harvesting systems, farmers can produce 384 kg of king prawns per hectare with an average size of 45 shrimp per kg… At the same time, 360 kg of barramundi can be harvested with an average size of six fish per hectare kg.
With these husbandry and harvesting systems, farmers can produce 384 kg of jumbo shrimp per hectare at an average size of 45 shrimp per kg. The farm gate price for this size is around IDR 83,000/kg (€5.07/kg), allowing farmers to earn IDR 31.8 million (€1,942) from the shrimp alone. At the same time, 360 kg of barramundi can be harvested, with an average size of six fish per kg. At this size, the farm gate price is around IDR 32,500 per kg (€1.99/kg), which means that barramundi farmers’ income can reach IDR 11.7 million (€715) per cycle.
The polyculture of tiger shrimp and barramundi undertaken by Mawardi and his 750 group members has become a model for other groups in the area, part of a government-initiated organic farming development covering 1,000 hectares.
Mawardi (second from left) with his group of farmers in Pinrang South Sulawesi
This polyculture system is also supported by the Ambon Mariculture Development Center (Balai Perikanan Budidaya Laut/BPBL) by providing good quality barramundi juveniles where previously farmers had relied on natural catches. Alongside 2019-2021, BPBL Ambon has distributed 250,000 barramundi juveniles to farmers so far.
*This article was written by Abdul Salam of BRPBAPPP Maros as an entry in a writing contest hosted by Minapoli
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