Case Studies- Fisheries

Recycling Bio-wastes in Fisheries - Possibilities in Assam

The concept of recycling organic wastes in aquatic resources is an age old practice.  Integration of pig-fish, poultry-fish, duck-fish systems and recycling farmyard wastes are some of the available options.

Goat rearing is a very old practice followed in Assam. The excreta of goat is rich in nitrogen and phosphorous. An adult voids about 750 gm of excreta in a day. Goat urine is also a rich source of nitrogen and potash.

Goat house should be constructed upon the pond embankment, with drainage facility to washout the waste materials into pond water. The goat dropping has a size around 4 mm pellet, coated with mucous which floats in semi-dried state and are consumed by the fishes. In 1.0 ha pond 30 – 40 nos. of goats are required to suffice the feed requirement of fish.

The most popular cross bred of high yielding strain found in Assam is Beetal, which is reared for both milk and meat purpose. There are other improved varieties available in India, which can be successfully reared such as Bengal, Deccani, Asomanabadi, Jakhrana, Sirohi, Jamunapari, Barwari, Marwari, Melsana, Surti, Malabari, etc.

The ponds are stocked with fish seed @ 6000 fingerlings/ ha. After 1 year of culture about 3500 kg of fish can be harvested. The farmer can earn additional revenue by selling the kids of goats.

Growing of horticultural crops on the pond embankment is popular in Assam. Various horticultural crops like banana, papaya, potato, Indian spinach, cow pea, okra, French bean, different kinds of gourds, cauliflower, cabbage, tomato, reddish, brinjal, turmeric, ginger, black gram, etc. are  cultivated.

The silt from the pond bottom is used as nutrient source for enhancement of yield from horticultural crops. The pond water is used to irrigate the crops. Banana leaves and residues from vegetables are used as food by grass carp. Fish seed are stocked @ 6000 fingerlings/ ha which gives a production of 3 t/ ha/ yr. From horticultural crops a production of 75 t/ ha/ yr is obtained.

Sericulture is practiced in certain specific areas of Assam. Integration of sericulture with fish is a profitable venture which increases the earnings of the farmers and creates round the year employment. Mulberry tree can be planted on the pond dykes for rearing silk worms. The waste products like silk worm pupae, faeces and waste water from the processing plants are nutrient rich resources and used as inputs for fish culture. The nutrients in the silk worm faeces enhances the growth of phytoplankton and heterotrophic bacteria, which are consumed directly or indirectly by filter feeding fishes.

The wastes from rice and wheat straws and hulls, sugarcane tops, stovers from maize, aquatic weed, etc. are obtained in large quantities. These are fibrous in nature and contain cellulose, hemicellulose, pectin and lignin. As these are not very palatable and digestibility being low they remain unused. After treatment, these wastes can be utilized in aquaculture for fish production.

The simple physical treatment involves chaffing and soaking the straws and then adding water soaked/cooked concentrate mixture. Alkali treatment, urea ensiling are some of the chemical treatments. Treatment with cellulolytic organisms like Trichoderma viride and lignocellulytic fungi like Pleurotus sp. and Coprinus sp. are some of the microbiological treatment which improve digestibility and provide the required protein. These wastes after processing can be recycled into pond water for fish culture @15 – 20 t/ ha/ yr to give a fish production of 2 t/ ha/ yr.

The recycling of bio-waste for fish culture is highly profitable. The use of bio-wastes that are readily available in huge quantities on farm helps to produce fish at a low cost.

Source: A training manual on "Polyculture and integrated fish farming", published by College of Fisheries, Assam Agricultural University, Raha - 782103, Nagaon, Assam

Spawning success stories with backyard aquaculture

A little care, proper planning and timely technical advice can bring amazing results for any farmer, according to Dr. V.A. Parthasarathy,

Director, Indian Institute of Spices Research, Kozhikode, Kerala. In that context, farmer Mr. K.K. Manoj's backyard freshwater prawn hatchery unit at Atholi in Kozhikode district, Kerala is a model worthy of emulation.

“I started with tiger shrimp farming near my house, and later switched over to brackish water breeds such as Pearl Spot, Mullet, and others as these fishes are available aplenty in the lakes near my house. I approached scientists at Peruvannamuzhi Krishi Vigyan Kendra (KVK) for help,” he says.

Knowing that brood stock (mother prawns) is available in the pond, the scientists put forward the idea of setting up a hatchery for breeding giant fresh water prawn in the farmer's backyard. “Even though a huge demand exists for post larvae of prawns, lack of availability, and the need for a huge investment make it difficult for many aspiring prawn farmers. Climate change, and many other contributing factors severely affect the natural breeding of fresh water prawns in many areas. The only solution is to breed them in captivity. So we trained the farmer to breed them in the backyard in small tanks,” says Dr. B. Pradeep, Subject Matter Specialist (Fisheries), KVK, Peruvannamuzhi.

Last year, Manoj set up a hatchery in his backyard on an experimental basis, the first of its kind in the Malabar area. Though these prawns are grown in fresh water, they require brackish water containing a specific salinity level for eggs to hatch, and grow through the larval period. “As per the advice of the scientists, I set up an artificial pool near my house using silpolin sheets and maintained the salinity of water in the tank at optimal level to create an artificial environment for spawning and larval development,” says Mr. Manoj.

“Around one lakh eggs are produced by a female prawn at a time, but only ten per cent survive to the post larvae stage. In the larval stage, they are fed with Artemia nauplii, a primitive, aquatic species largely found in salt water. Mr. Monoj's determination and hard work plus timely scientific intervention showed good results,” says Dr. Pradeep. “On an experimental basis I sold around 5,000 post larvae prawns in the first stage,” says the farmer proudly and adds “I am planning to expand the hatchery.”

Recently, the Indian Institute of Spices Research felicitated Mr. Manoj at its annual Karshika Sankethika Darshanam 2011, a farmers mela and technology expo for his innovation in developing low cost fibre cages for rearing Pearlspot fishes in captivity. “Normally, these fibre cages are made of fibre wire mesh. PVC pipes are used to float these structures on water. Since PVC pipes are very costly, I used empty plastic bottles to replace them. The bottes help the cage to float on the water surface,” explains the farmer.

The production cost for a standard fish culture cage works out to more than Rs. 3,000 rupees, whereas the low cost model is priced at only Rs.1,000. With a full-fledged Pearlspot hatchery unit, the innovative farmer produces around 20,000 fingerlings each breeding season. “There is a good demand for Pearlspot from small scale farmers. I am getting around Rs. 5 for each fingerling,” says Mr. Manoj.

According to Mr. Manoj, pearlspot farming in captivity is profitable as it requires minimum investment and harvesting is easy. Even small scale farmers and women can grow them in the backyard.

For more details contact Mr. K.K. Manoj, Koodathumkandi House, Velur Post, Atholi (Via), Kozhikode- 673315. mobile: 09387527887 and Dr. B Pradeep, email: kvk@spices.res.in, phone: 0091-496- 2662372.

Source : Backyard Aquaculture, Agriculture Column, The Hindu

Wastewater Treatment through Aquaculture

With the increasing population in the country, the quantity of wastewaters generated has been increasing beyond the treatment capacities, apart from host of industrial effluents and solid wastes in recent years. Intense efforts are being made at treating the domestic sewage to make the effluents suitable for discharge into the natural waters.

Concept of biological treatment

• Biological treatment involves systematic use of natural activity of the bacteria for biochemical reactions, resulting in oxidation of organic matter into CO2, H2O, N2 and SO4.
• The processes used widely for treatment of domestic sewage are activated sludge and trickling filter methods, oxidation/waste stabilization ponds, aerated lagoons and variations of anaerobic treatment systems;
• The latest one is the Upflow Anaerobic Sludge Blanket (UASB) process. The traditional practices of recycling sewage through agriculture, horticulture and aquaculture, being basically biological processes, have been in vogue in several countries. The sewage-fed fish culture in bheries of Calcutta is world-famous. The emphasis in these practices has been on the recovery of nutrients from the wastewater.
• Taking cue from these practices and deriving from the new databases in different disciplines of wastewater management, aquaculture is being proposed and standardized as a tool for treatment of domestic sewage.

Treatment Process

The wastewater treatment system through aquaculture includes sewage intake system, duckweed culture complex, sewage-fed fish-pond, and depuration pond and outlet systems.

• The duckweed culture complex comprises a series of duckweed ponds where aquatic macrophytes like Spirodela, Wolffia and Lemna are grown. The wastewater is taken on gravity or pumped through intake system into duckweed culture system where it is retained for 2 days before allowing to fish-ponds.
• The model developed for treatment of 1 MLD wastewater consists of 18 duckweed ponds of 25 m x 8 m x 1 m, constructed in 3 rows, thus allowing water to pass through a series of three duckweed ponds into fish-ponds by gradient.
• The system includes 2 fish ponds of 50 m x 20 m x 2 m and two marketing ponds/depuration ponds of 40 m x 20 m x 2 m. the system receives primary treated sewage, after removal of solid materials.
• On the other hand, the treatment systems operated at two different locations of Bhubaneswar city for treatment of 8 MLD sewage, however, is designed with certain modifications for handling large volume of wastewater.
• As the optimum intake BOD levels for effective treatment are in the range of 100-150 mg/l, it may be necessary to incorporate an anaerobic unit where organic load and BOD levels are very high.
• The duckweed culture unit helps in removal of heavy metals and other chemical residues that otherwise get into human food chain through cultured fish. These also serve as nutrient pumps, reduce eutrophication effects and provide oxygen from their photosynthesis activity. The wastewater with BOD5 levels of about 100 mg/l can be treated with a total retention time of 5 days, with final BOD5 levels brought down to 15-20 mg/l, meeting the required standards of different parameters for discharge into natural waters.
• Further, taking advantage of high productivity and carrying capacity in sewage-fed system, production level of 3-4 tons of carps/ha is achieved in fish culture ponds. The system provides for a biological treatment system with high potential of resource recovery in terms of duckweed and fish. The main limitation of this biological treatment system, however, is the reduction of efficiency of treatment during the winter period and the regions with temperate climatic condition. Comparatively low requirement of land of about 1.0 ha for treatment of 1 MLD sewage and resource earnings partially meeting working costs, makes the system an ideal one for treating wastewater before discharge into natural waters.

Economics of 1 MLD treatment capacity