Aquaculture is recognized as a very efficient form of animal production system. Improvement in fish yield while sustaining the natural resources, depends to a great extent on the appropriate husbandry practices adopted.
Aquaculture is a highly diverse production system. The diversity of aquaculture production is reflected terms of holding units (ponds, tanks, raceways, cages, pens etc); management levels (extensive, semi-intensive, intensive, super-intensive); nature of rearing (monoculture, poly-culture); salinity levels (freshwater, brackish and marine); climate (cold water aquaculture, warm water aquaculture) and state of motion of water (static systems and flow-through systems). Earthen pond aquaculture, however is the most common, but other efficient production systems such as tank culture, cage culture, raceway culture, integrated culture, and pen culture among others are widely used worldwide.
Ingenuity of farmers’ innovations and improvements successfully tested over time should be given due recognition, lest such innovative ideas and spirit get lost for ever.
Freshwater aquaculture is a viable rural activity in India. Its contribution towards food provision of very high biological value and livelihood improvements hardly needs any emphasis. Mass production at reduced cost of operation will make aquaculture more remunerative for the farmers. This will have economic as well as ecological significance. The country’s fish production, which is second in the world, is greatly contributed by small and marginal farmers.
The key factors influencing the production are (a) appropriate pond management (b) a good breed of stocking material of right size and proportions (c) farm-made feeds using locally available agro-based ingredients and appropriate feeding strategies. Sustainable yield increase especially in small scale aquaculture is expected primarily from optimization of inputs used. This can be achieved through adoption of simple scientific principles and management measures wherever possible. Earlier, in the absence of a precise knowledge on the control of reproduction and breeding, farmers resorted to collection of larvae and juveniles from rivers for stocking in the culture ponds. Practices like ‘Bundh breeding ‘where a sudden gush of rain water is forced into the spawning ground were and are even today used to induce natural spawning. Subsequently, with the advent of induced spawning technique to breed the fishes in a consistent manner, simple improvements in hatchery technology for mass breeding followed by genetic selection procedures accelerated the development of carp aquaculture in particular through availability of stockable seed almost throughout the year.
Farmer innovative practices
Use of simple tools and implements accompanied by continuous farmers’ creative ideas in the fish husbandry process and skill of problem solving proved to be quite successful and stood the test of time. Farmers in some of the districts in West Bengal like Bankura, north 24 Parganas; south 24 Parganas, south Dinajpur, east Burdwan; Hooghly, Malda and east Medinipur, have been practicing fish production using traditional wisdom and simple indigenous innovative devices. Some of the innovative practices of fish farmers are listed in Box 1 and some of them are described below.
- Depletion of dissolved oxygen (DO)content in pond /tank water is a recurring problem in aquaculture . In case DO level dips down to 3.0 mg/litre, water becomes stressful for the fish to live in and large fishes particularly carps come to the water surface to breathe desperately. This generally happens early in the morning and that too during the days when normal bright sunshine is not there or when cloudy weather conditions Such problem can be fatal and the farmer may lose the entire crop of fish unless emergency oxygen is supplied. Since farmers do not have crop insurance they cannot afford to buy expensive mechanical aerators. A simple device using bamboo baskets put in a cascade pattern, tied with 3 bamboo poles and affixed in the pond with 0.5 HP pump connection attached to hosepipe is used to make good oxygen deficiency in water in a short time. This saves money and the cultured fish also.
- Many resource poor farmers in West Bengal villages prefer growing advanced fingerlings ( av. wt. of fish during harvest is 100 g.) from fry stage . The culture period is of 3 months duration. When fish is harvested, the pond is restocked the very next day, enabling farmers to grow 3 crops a year. With continuous demand, farmers also get their returns quickly. However, the predator birds like kingfisher, cormorants, herons pose threats for fish survival. To overcome this, farmers use simple threads, spreading over the culture ponds. This has been found to be very effective and environmentalists also do not object to this process of preventing bird predation as it does not harm the birds too.
Box 1: Other innovative practices
- Creating a shade on the pond with the help of palm leaves during summer months when heat become unbearable.
- Measurement of water quality parameter -like turbidity using fabricated secchi disc.
- Fortnightly application of medicated feed containing herbal extracts like neem leaves, turmeric, basil leaves, garlic mixed with pinch of common salt, to prevent disease infestations.
- Periodic removal of generated gases from the pond bottom using rakers followed by lime application to maintain water quality parameters within recommended levels.
- Although carp or the Indian major carp species –catla, rohu, mrigal are the main cyprinids cultured throughout India in the freshwater sector, small indigenous fish species like air-breathing catfishes – magur and singhi , murrels like Channa sps., perch like koi, feather-back like folui eels like pakal ,small local fishes like mola, tangra, pabda khoira, vacha are in very high consumer demand. Hence farmers prefer crop diversification. Installing bamboo cages in ponds enables farmers to go in for multiple species culture without facing problems in feeding or harvesting.
- Since feed the most expensive input in any aquaculture system , small farmers who have no option than to go in for low external input culture system, prefer growing fish based on natural food organisms like natural zooplankton , periphyton and the like. Using organic manure prepared in situ and sometimes stuffed in hollow bamboo poles or bamboo sticks wrapped with discarded sugarcane bagasse affixed at several locations of the pond is found quite useful for the fabulous growth of periphyton- the preferred natural food for rohu. These form part of organic aquaculture also which is a currently growing trend .
- Small farmers of most West Bengal villages with small and medium sized ponds, use simple feeding devices. One of them is the use of perforated nylon bags hung with the help of bamboo poles in ponds. This is widely used feeding practice in semi-intensive carp polyculture.
- Fish feed, in the form of chowmein /spaghetti, is prepared using locally available agro-based by-products. These are prepared using locally made devices and sun dried and stored in gunny bags. Tribal youth and small farmers are adept in preparing such local feed, both for their own enterprise as well as a business option too.
- Farmers generally remove the aquatic macrophytes, physically from the pond and do not use weedicides.
Oflate, farmers are instead encouraging the growth of plants like Ipomea which is considered delicious. Growing azolla and duckweeds have served as feed for fish and also as a biofertilizer. All such practices have helped the farmers to grow human food of very high biological value at a relatively low production cost making the entire state a model for inexpensive low external input aquaculture.
While there is no denying that application of scientific principles is important in the scaling up of the production performance of cultured fishes, ingenuity of farmers’ innovations and improvements successfully tested over time should not be overlooked and given due recognition, lest such innovative ideas and spirit get lost for ever.
Retired Principal Scientist, ICAR-CIFA ( www.cifa.in ),Bhubaneswar
185,Sreerampur Road ,Kobasia Vin ,Block-B-309 ,Garia,Kolkata=700084 .