Type of ponds in aquaculture

 4.0         Pond types and their characteristics

 

Ponds are small and shallow bodies of quiet standing water with only slight wind action. In ponds extensive occupancy of higher aquatic plants is common characteristics.  No exact limit of area and depth has been laid down for a pond. Usually the depth of fish culture ponds are less than 2.5 meters. From fish culture point of view ponds are generally used to rear seed from one stage to another advanced stage and for production purpose. Several classification systems can be used to simplify discussion and allow comparison among ponds types like species of  fish being cultured (Carp, cat fish and shrimp), life stage ( larval, fingerling and brood fishes) salinity preference (freshwater, brackish water and salt water) and climatic or temperature regime ( tropical, warm water  and cold water ponds). Mainly the ponds based on culture stages of fish and construction are as follows.

 

4.1. Nursery ponds:- Nursery ponds refers to the rearing ponds where 3-4 days old larvae (5-6 mm) are reared for a period of 15-20 days till they grow to fry(20-25mm) stage. Generally smaller seasonal earthen ponds of 0.02 to 0.1ha (200 to 1000m²) size with average 1.0-1.5 meter depths are preferred for carp nursery. Concrete tanks of 50-100m² provided with a soil base of 15-20 cm are also used for rearing carp fry. The stocking density of spawn is kept around 1-10 million /ha. The degree of survival in properly managed ponds ranges from 50-90 %. Diet for carp spawn must contain 35-40 % protein, 4-6 % crude lipid, 22-26% carbohydrate, B- complex vitamins0.1%, vitamin-C 600mg/kg food, vitamin –A- 200 IU/kg. The amount of feed applied in nursery pond is 400 % of the initial spawn biomass (one million spawn weight about 1.5 kg). 6.0 kg of feed is required /million spawn/day tor first 5 days and 800 % of the initial spawn biomass i.e. 12 kg/million/day for subsequent days.

            The fry are harvested during morning hours. They are kept in crowded condition for 2-3 hours in hapa to minimize faecal matter load during transportation. One third of the polyethylene bas are filled with water and two third is filled with oxygen to keep the seeds alive for 20-24 hrs journeys.

 

4.2. Rearing ponds:- Fry of carps measuring 20-25mm are raised further for 2-3 months to raise fingerlings. It is done in relatively larger ponds of 0.05 -0.2 ha with 1.2 to 1.5 meter depth. The food preference and feeding habits of carps gradually changes during this stage and they occupy different food niches that are top, bottom and column layer.

            Rearing ponds are properly prepared (eradication of weed and predatory fishes, aquatic weeds, manuring, fertilization and for presence of planktons). Raw cow dung is applied @of 5-10 t/ha depending upon organic carbon load of the soil. If poultry droppings are used in place of caw dung the amount is reduced to half amount of the amount of cattle-dung. Further urea, single super phosphate and potash are applied that improve the growth of planktons.

            Fry are stocked @0.2-0.3 million fry /ha. If aeration, water exchange and other management support are available then stocking density can be improved. Various stocking ratios have been evaluated. Suggested combination of species are Catla: Rohu: Mrigal in 1:1:1 or 1:2:2 or 3:4; Silver carp: Grass Carp: Common Carp can be stocked in 4:3:3or 1:1:1 when  Six species rearing is followed the stocking density can be 1:1:1:1:1:1:1.

            In addition to natural food present supplementary food consisting of oil cake and rice bran in 1:1 ratio by weight are supplied 8-10 % of fish biomass present per day during first month of fry rearing. This quantity of feed is reduced to 6-8 % for next two months. The daily ration is provided in two equal parts and fed during early morning and evening time. A part of the ration is powdered and hand broad casted for surface feeding fishes and rest of the ration part are kept in feeding tryas. Duck weeds like Spirodela, Lemna, Wolffia are provided when grass carp is also stocked with other fishes.

Fish health is regularly monitored/observed for occurrence of any parasitic (Myxobolus, Trichodina, Argulus), bacterial (Aeromonas, Favobacterium, Pseudomonas, Vibrio, Renibacterium etc) or fungal (Saprolignia, Aphanomyces etc ) infection if any. The water quality parameters are like dissolve oxygen (DO), alkalinity, hardness, temperature, CO₂, H₂S, total suspended solids and total dissolved solids are monitored to be in optimum range. Lime and fertilizers are applied as per the requirement. Water seepage loss, evaporation loss is periodically compensated. In case of any problem the treatment major can be taken as per requirement.

           

Within two to three months of rearing fry they grow to fingerlings of 80-100mm in length. Normally a survival of 60-70% is achieved in rearing ponds with proper management. Feeding is stopped one day prior to transportation and they are kept in crowded condition to evacuate their gut. This help in transportation as less faecal matter release maintains the water quality to a desired extent. The fingerlings are harvested during morning hours preferably. Stunted fingerlings are also reared at higher stocking density with low rate of feeding to ensure year around availability of fish seed.

 

4.3. Grow out ponds:- Grow out ponds are earthen ponds because there area is comparatively more. Area for grow out ponds may vary from 0.04 to 10 ha and with 1-4 meter in depth. Ponds from 0.4 to 1.0 ha sizes with water depth between 2-3 meter are considered ideal.  The carp fishes feed on the base of the food chain therefore utilize natural productivity with greater output. The polyculture of 3 Indian Major Carp (IMC) results in lower production level than six species composite culture system. The carps are also  cultured under mixed culture system incorporating freshwater prawn (M.rosenbergii, M.malcolmsonii) and cat fish like (C.batrachus) and (H.fossilis). The production level is affected by the species combination, proper pond preparation, pre and post stocking management, water quality and health management and level of input in the pond.

 

4.4. Pond based on type of construction

 

4.4.1. Levee or embankment pond:- These are most common ponds built on flat land by excavating a thin layer of soil from the pond bottom and using that soil to form levee or embankment around the pond perimeter catchment areas for rainfall and runoff are small consisting only of the pond surface and the inside embankment slope. So there must be source of pumped water to fill these ponds. They can be made of any size and shape.

 

4.4.2. Excavated ponds :- Excavated pond are usually smaller and the elevation of the pond is further below the original ground level of embankment of the pond. In high water table areas ponds may be partially filled with ground water inflow. Emptying excavated ponds may require pumping to lift water inflow and to lift water into drainage canals.

 

4.4.3. Watershed ponds:- Watershed ponds are built on hilly terrain by draining a temporary or permanent stream. The major source of water is runoff from the catchment basin above the dam which can vary from constant inflow when a permanent stream is dammed to highly variable inflow when the watershed is small. Water levels may vary greatly. It is runoff water that maintains the water level during dry season.