Fish pond management involves preparation of the fish ponds, stocking, feeding, maintain good water quality, fish sampling, maintenance of the pond structures, fish harvesting and record keeping.
The success of any enterprise (including fish farming) depends mainly on good management in order to maximize profit. To achieve maximum fish production, fish pond must be properly managed.
Steps for Fish Pond Management
1. Fish Pond Preparation
Drying the pond bottom: The pond must be completely drain of water and the bottom allows drying until it cracks. De-silting of the pond is carried out if the pond is very muddy.
Repair of pond structures: The embankments, monks, fish screens and water supply structures are checked and repair carried out before the pond is filled with water. Eroded dykes are strengthened or water filtering structures if clogged are thoroughly cleaned or replaced.
Removal of unwanted organisms and aquatic weed: While the pond is being dried undesirable organisms e.g. frogs, mollusks, fish predators are eliminated. They are prevented from entering the pond by use of proper screens at the inlets or fencing the farm/pond and keeping the surrounding vegetation low.
Dense aquatic vegetation occurring either along the pond margin or inside the ponds are controlled. These weeds compete with phytoplankton for the nutrients available in the water and hence diminish pond productivity. Aquatic weeds can be removed manually, mechanically (using rakes) or biologically (using grass eating fish e.g. Distichodus).
Liming: Lime is used to improve the pond bottom, and to kill parasite or undesirable organisms in the pond. It also prevents water from becoming too acidic. Liming increases the alkalinity of the water, thereby increasing the availability of carbon dioxide. Materials use for liming and their rates of applications are:
Quicklime (caustic lime) = 200 – 500 kg/ha Slake lime (Hydrated lime) = 300 – 500 kg/ha
Agricultural lime (limestone) = 500 – 2000 kg/ha.
The lime material should be finely ground and is spread over the entire dry pond bottom. After liming, the pond is left to dry for 1 – 2 weeks to ensure proper mixing of lime with the soil.
Filling of water): The pond after liming is partially filled with water to a depth of 0.6m and left for 2 – 4 days to observe any leakages or seepage. It is later completely filled up and fertilized.
Fertilizer application: To make water more productive, fertilizers are added. They contain important nutrients which help in production of natural fish food organism (plankton). There are two basic types of fertilizers: organic and inorganic.
2. Stocking
Stocking a pond means releasing into the pond an adequate number of selected fish species which are of the right size. The fish pond is stocked a week after fertilization. The stocking density of the pond depends on the fish culture system adopted and the species cultured.
Generally for pond culture and for species which do not reproduce early, the stocking rate vary from 1- 3 fish/sq.m (i.e.10,000 – 30,000 fish/hectare). However, stocking rates can be higher with high technology.
In stocking fish ponds; monoculture (one type of fish) or polyculture (mixed fish species) can be adopted. For polyculture systems, the following stocking ratios may be used.
Tarpon + Tilapia = 1: 2
Mudcatfish + tilapia = 1: 3
Grey mullet + tilapia = 2: 1.
Fish fingerlings for stocking ponds can be produced by the farmer or purchased from reputable hatcheries. The ponds are stocked either early in the morning or late in the evening. This is to avoid stressing the fish during hot weather.
The total number and weight of fish stock are recorded. The fish pond is checked the next morning for any mortality. Dead fish are removed, counted and replaced with live one.
3. Feeding
In the water natural food is available to the fish. Some fish e.g. Heterotis, Tilapia feed on microscopic plants or soft plant parts and are called herbivore.
Some feed on other aquatic animals as well as fish and are called carnivore e.g. Tarpon, Niger perch, while others feed on both plants and animals and are called omnivore e.g. Mudcatfish.
In culture systems, fish is given supplementary or artificial diet to make them grow faster. There are a variety of fish feeds formulated from different feed ingredients. Feeding of fish is carried out by broad casting at selected spots 9 feeding spots) in the pond.
Automatic or demand feeder may be used. Pelleted feeds are preferred to powdery feed. However, the size of the pellets must not be too big for the fish to swallow.
4. Fish Sampling
Periodic check on fish growth is vital for pond management. Monthly or bi-monthly fish sampling is carried out to check growth rate and to calculate the feed ration.
During sampling, a small quantity of the fish stock is scooped out, counted, weighed, and returned to the pond. Any fish showing signs of disease condition is removed for thorough examination
Read Also : Guide to Proper Fish Pond Construction
5. Harvesting (Cropping)
Harvesting a fish pond is undertaken when the fish stock or part of it has attained marketable size. Market size of fish is determined by consumer acceptability and preference. Most culturable fish species; with proper feeding and good management attain market size within 6 – 9 months of stocking.
Cropping of pond can be partial, that is, removal of bigger fish and allowing the smaller one to grow to the desired size or complete (total) i.e. removal of all fish in the pond. Feeding is stopped 2- 3 days before cropping.
The pond is completely drained and fish scoped out. They are sorted into different sizes and/or different species, counted and weighed. Small fish are returned to the nursery ponds for stocking. Tools used for stocking include seine or drag nets, scoop nets, traps, hook and line etc.
6. Marketing and Fish Preservation
Harvested fish can be marketed live, smoked of frozen. Fish can be sold direct to the consumers or through a distributor.
It may be necessary to advertise fish sales to minimize high post-harvest lose. Unsold fish (live) can be preserved by storing in deep freezers or cold rooms. Smoking’s, sun-drying, salting and canning are other methods of fish preservation.
7. Record Keeping
It is important for the fish manager to keep accurate records of all fish farm activities. Such records may include labour cost, cost of lime/fertilizer and rate of application; cost of fingerlings and fish feed; harvest and sales.
Fish farm records aim in good farm management and in evaluating the economic viability of the project.
In general, fish ponds require management and maintenance. Here are some of the basic practices that should be followed;
1. Keep unwanted fish out of the pond
Carnivorous fish can eat fingerlings stocked into a pond (Figure 6). Other wild fish will compete with stocked fingerlings for food causing slow growth. Wild fish should be removed from fingerlings being stocked into a pond.
Pond water inlets should be covered with a fine mesh screen or similar materials to prevent entry of wild fish. Screens should be inspected daily and cleaned if necessary to prevent clogging.
The pond should be completely drained and dried (preferably until cracks appear in the mud) before refilling and stocking new fish. Any fish remaining in undrainable areas may be killed with poisons which are not dangerous to humans.
2. Lime and fertilize the pond
Natural fish food organisms are usually not abundant in clear pond water, but are abundant in ponds having greenish colored water. The green color indicates the presence of phytoplankton and other natural food organisms.
Liming (Figure 8) and fertilization help increase the abundance of these organisms. Lime is not available in many areas and may not be necessary if the pond soils and/or water are not acidic.
Soil and water may be tested in a laboratory or with a kit to determine whether liming is required. Testing for acidity can save a farmer time, labor and expense. An agricultural extension agent should be contacted for information on soil and water testing and lime requirements.
Chemical and organic fertilizers may be applied separately or in combination to ponds (Figure 7). Figure 7 illustrates a useful technique for determining whether enough fertilizer has been added to a pond.
Numerous factors are linked to the effectiveness of liming and fertilization on stimulating natural fish food production.
A common misconception about growing fish in ponds is that fish require continuously flowing water. Fresh water is added to a pond only as needed to correct poor water quality, as will be mentioned later, or to replace evaporation and seepage.
Excess water flow washes out fertilizer nutrients and inhibits plankton growth. Diversion canals channel excess water away from ponds and prevent fertilizer nutrients and natural food from being flushed out of the ponds.
3. Stock the right number of fish
The proper number of fish should be stocked into ponds to ensure good fish growth and yield (Figure 10).
Overstocking results in crowding and slow growth. Understocking results in poor utilization of natural food organisms in the pond and low fish yield. Proper stocking rates for tilapia range from 1 to 2 fish per m2 of pond surface area.
Common carp are stocked at 1 to 2 fish per 10 m2 of pond surface area. The higher stocking rate is used for both tilapia and carp when fish are given supplemental feed. Stocking more than 2 carp per 10 m2 will cause the water to become muddy as a result of bottom feeding activity.
8. Feeding Your Fish
Fish in fertilized ponds will grow faster when they are provided with supplemental feed. Tilapia and carp will consume a wide variety of feeds, many of which are available to rural farmers.
Examples of supplemental feeds are rice bran, wheat bran, corn gluten, African palm seed meal, dried and ground leaves from mullberry and ipil-ipil trees and manioc plants, dried blood, chopped earth worms, termites, chopped snails and insects.
Two daily feedings (morning and mid-afternoon) are suitable under most situations. The amount fed depends on the number of fish stocked and their average weight.
Fingerlings are generally fed 10 to 12 % of their body weight. The feeding rate is gradually reduced to 2 to 3 % of body weight by the time fish reach market size.
In summary, proper fish pond management is imperative for an effective and productive ventures. Fish pond management involves preparation of the ponds, stocking, feeding, and maintaining good quality water, fish sampling, maintenance of pond structures, fish harvesting/marketing and record keeping.
Read Also : Methods of Fish Fecundity Determination
Glossary of Terms for Fish Pond Management
Anti-seepcollar– a plate, usually constructed of cement or steel, which is attached around a drain pipe and extends about two feet outward from it. It is buried in the pond dike to retard the seepage of water through the dike along the drain pipe.
Chemical fertilizers– manufactured fertilizers containing nitrogen, phosphorous and potassium in varying proportions.
Fertilizer– a substance added to water to increase the production of natural fish food organisms.
Fingerling– a fish weighing from 1 g to 25 g or measuring longer than 2.5 cm in total length.
Fishtoxicant/ poison– A substance used to kill fish in ponds prior to stocking fingerlings.
Organic fertilizer/manure– animal or plant matter used as fertilizer in ponds.
Natural fish food organisms– plankton, insects and other aquatic organisms that fish eat.
Oxygen depletion/low oxygen – a condition, normally occurring at night, in which oxygen dissolved in pond water has been depleted mainly because of the decomposition of organic matter and respiration of organisms in the pond.
Phytoplankton– the plant component of plankton.
Plankton– the various, mostly microscopic, aquatic organisms (plants and animals) that serve as food for larger aquatic animals.
Ponddike– the wall of a pond which is constructed to hold in the water.
Predatory/carnivorous fish– a fish species that eats other fish.
Supplemental/ incomplete feed – a feed that does not contain all the vitamins and nutrients essential for growth, and which is produced outside of the pond.
Read Also : Importance of Water and Its Unique Properties
