Freshwater Shrimp Farming is Feasible
Brackishwater tiger prawn(Penaeus monodon) farming is an established industry, while giant freshwater prawn(Macrobrachium rosenbergii) farming is still in the development stage in the country.
Aside from brackishwater tiger prawn or sugpo and giant freshwater prawn or ulang which require costly hatchery facilities and feeds to produce, we have indigenous freshwater shrimps like the Macrobrachium idella that does not grow as big as the prawns but is cheaper to farm.
M. idella is a medium-sized shrimp found in many of our lakes, rivers, and dams. Due to overfishing and destruction of its habitats, however, wild populations of the shrimp have dwindled.
In Lake Bato of Camarines Sur and Albay, the M idella is harvested in commercial quantities, according to researcher Edna Agasen of the National Fisheries Research and Development Institute. The species breeds in the lake throughout the year but the peak months are March and April. Fresh shrimps are sold at P40-P60 per kilo depending on size (males are bigger than the females), while the dried shrimps are priced at P60-P80 per kilo.
The first report on the maturation and breeding of M idella in captivity was made by this writer and Eunice Villanueva at the Freshwater Aquaculture Center of the Central Luzon State University (FAC-CLSU) in 1978. Maturation and breeding of the shrimp in freshwater ponds were observed. Eggbearing females placed in aquaria with well-water(less than 1ppt salinity) produce juvenile shrimps in 21-31 days.
It was clearly shown that unlike bigger prawns, M. idella can reproduce itself entirely in freshwater without the need for expensive hatchery and nursery facilities requiring saline waters.
Being a plankton-feeder, M. idella can be cultured in freshwater ponds with organic and/or inorganic fertilization, although supplemental feeds can be given to hasten its growth.
A study done at the FAC-CLSU showed that stocking of 44 adult M. idella with average weight of 10 grams in a fertilized 0.1-hectare pond produced over 2,700 young shrimps with a total weight of 16.49 kilos after nine months of culture. In another pond stocked with 200 juvenile shrimps with an average weight of 2.7 grams, more than 400 young were produced with a total weight of 4.97 kilos (including the adult shrimps) after 136days of culture. These indicated that stocking of adult shrimps can produce more young than stocking of juveniles and that the maturation of the shrimps is achieved in less than four months.
The M. idella can also be polycultured or grown together in fertilized ponds with the Nile tilapia(Oreochromis niloticus), according to a study done Luzviminda Guerrero of Aquatic Bosystems in Bay, Laguna. She found that stocking of fingerlings at two per square meter and adult shrimps at four per square meter produce the equivalent of 600 kilo per hectare of tilapia and 45 kilos per hectare of the shrimp after four months of culture.
Supplemental feeding has been found to increase freshwater shrimp production in ponds. Feeding of tilapia with an artificial feed (20 percent crude protein) in a polyculture system increased the yield of the shrimp by 28 compared with no feeding. When the shrimp was fed with dried ayungin (Therapon plumbeus) and African nightcrawler (Eudrilus eugeniae), it was found that the earthworm gave a higher total gain, lower feed conversion. and a greater production of juveniles than the fish.
Here are tips for pond operators who would like to try freshwater shrimp farming.
1. Prepare the pond properly so that no predators like catfish and goby are present.
2. Fill the pond to a water depth of at least 0.6 meter.
3. Fertilize the pond with dried chicken manure in sacks suspended in the water at 500 kilos per hectare every two weeks to promote the growth of plankton.
4. Procure your initial M idella breeders (5-10 grams) from local sources and stock at the rate of 2-4 per square meter with a sex ratio of 1-2 females per male (bigger in size with longer arms).
5. Provide brush shelters (made of bamboo or tree twigs) or allow the growth of submersed aquatic weeds like digman to serve as refuge for the shrimp when molting (shedding of shell) and increase surface area for growth of food organisms.
6. Culture it for at least four months.