Introduction to Catfish (Ikan Keli)
Catfish (order Siluriformes) are a very diverse group of bony fish. Named for their prominent barbells, which resemble a cat's whiskers (though not prominent in all members of this order), catfish range in size and behavior from the heaviest, the Mekong giant catfish from Southeast Asia and the longest, the wels catfish of Eurasia, to detritivores (species that eat dead material on the bottom), and even to a tiny parasitic species commonly called the candiru, Vandellia cirrhosa. There are armour-plated types and also naked types, neither having scales. Despite their common name, not all catfish have prominent barbels; what defines a fish as being in the order Siluriformes are in fact certain features of the skull and swimbladder. Catfish are of considerable commercial importance; many of the larger species are farmed or fished for food. Many of the smaller species, particularly the genus Corydoras, are important in the aquarium hobby.
A Note to Non-Farmers
residents. Most farmers were born and raised on a farm. Very few learned how to farm as an adult. This puts the non-farmer at a considerable disadvantage.
Non-farmers will need to go through a period of on-the-job training. Are you the kind of person who does most of the maintenance and repair work? Can you put up with outdoor work during bad weather and odd hours? If so, great - these are skills and tolerances you will need on a fish farm. If not, you may wish to reconsider before getting into fish farming. In addition, farming today requires much more than just being able to produce a crop. Successful farmers must have a sound understanding of the economics of their operation, keep good records and work to find the best markets for their product.
Catfish farms that are only a few acres in size and where the operator has plenty of time will usually earn the highest return by selling fish direct to the consumer. Larger farms will sell most of their fish to processors, but can still increase their profits by selling some of their fish to buyers that pay a higher price such as fee-fishing pond operators.
• Healthy Large Fingeriings - Six to eight inch long fingerlings must be purchased if marketable catfish are to be produced in one growing season. Good quality 6 to 8 inch fingerlings are 11 or fewer fish per pound. Visit your fingerling supplier’s farm to inspect your order before it is loaded. Be sure no wild fish are mixed with your order.
• Good Feed - Buy a high quality complete feed made for catfish with at least 32% crude protein. Many cheap catfish feeds are intended for use in recreational fishing ponds where fish are stocked lightly and can obtain natural food to make up for anything missing in the feed.
It takes know-how and long hours to manage a fish farm. A good farming background that includes operation and maintenance of equipment is important. Fish farmers must also be comfortable with the close attention and stress that goes along with managing an intensive agricultural operation. Like any other animal in a crowded feedlot situation, catfish are susceptible to sickness and poor production if poorly managed. The manager must closely watch how the fish are feeding and the condition of the water both by test equipment and color. During summer, nightly rounds to monitor oxygen levels and aerate ponds are the norm, not the exception. On the positive side, catfish farmers have the satisfaction of watching the fish grow from fingerling to harvest size and knowing that it is directly due to their management.
Fish farms require large volumes of good quality water. The water required for levee ponds can be estimated as either a minimum of 13 gallons per minute of flow for each surface acre of pond or 3 times the pond volume per year. When considering other sources, such as streams and watershed reservoirs, get the advice of a Soil engineer (If you can find one). Wells or springs are the preferred source of water for catfish ponds. Run well and spring water over screening or splash boards to increase oxygen content. Water from streams and lakes must be screened to keep out wild fish, which would otherwise reproduce and compete with the catfish for feed and space.
It is not practical to analyze every possible water quality variable and contaminant that might make water unfit for fish farming. The best way to evaluate water is to grow a few catfish in an aquarium filled with the water or in a cage suspended in the water. Laboratory tests for total alkalinity, total hardness, total iron, nitrate and salinity can also be useful. Table 1 gives recommended ranges for these water quality variables. Seek further advice if water quality values are outside of the recommended range. Situations to avoid in selecting a water source include:
1. Surface water sources subject to pesticide pollution. Streams and lakes bordering agricultural land may receive pesticides in the form of runoff or spray drift.
2. Deep wells or other water sources with high pumping costs. Estimate annual pumping costs before committing yourself to use a water source.
3. Watershed impoundments that are too fertile. A heavy growth of microscopic plants (phytoplankton) giving water a dense green or brown color is an indication of this problem. Fish kills due to low oxygen are more likely in such water.
The key to maintaining good water quality is to measure the surface acreage of each pond exactly and not stock more than the recommended number of fish per surface acre. Extra fish mean extra nutrients going into the pond in the form of feed. This leads to heavy growth of microscopic plants (phytoplankton) which die and decay leading to lack of oxygen and sudden large fish kills. To maintain water quality over the long term, many farmers drain their ponds every 5 to 10 years, allow them to dry and then scrape out the organic material that has built up on the bottom.
The suitability of soils for pond construction can usually be determined by your county Soil Conservation Service office from a published soil survey. Soils should contain 30 percent or more clay and have low permeability rates. Soils that are almost pure clay may not be suited to pond construction due to their poor compaction properties and high shrink-swell potential. Situations to avoid in selecting pond sites include:
1. Areas that are subject to frequent flooding.
2. Areas with rock outcroppings.
3. Soils that may contain persistent pesticides or other toxic substances present in the soil. Past use of the site for cotton farming, cattle dips or waste dumps are warning signals. Persistent pesticides that have made newly built ponds unfit for catfish include Endrin and Toxaphene.
4. Locations that are too isolated to allow good security. Fish farmers are always in danger of losing fish to midnight poachers.
Watershed ponds are constructed on steeper slopes by building a dam across a draw or ravine to catch runoff water. If built with a fairly flat bottom they can be used for commercial catfish farming. To avoid weed problems, water depth should be a minimum of 4 feet. A disadvantage to most watershed ponds is the lack of control over refill. One way around this is to build a series of ponds, one above the other. The lowest pond is harvested first, so as higher ponds are drained they fill the one below.
Deep ponds are likely to experience low oxygen problems in the fall when oxygen poor bottom water mixes with upper water. Because of this problem, ponds with an average depth of more than 6 feet should not be stocked with more than 2000 catfish per surface acre, unless special equipment is used to keep top and bottom waters mixed.
Cages are used to grow catfish in existing ponds and lakes where harvesting loose stocked fish would be difficult or impossible. Catfish can be stocked into cages at eight to ten fish per cubic foot and grown to a size of 1 to 2 kg. Catfish do well in cages provided that they are not disturbed, the cage mesh does not become clogged with algae (“moss”) and no more than 1,000 kgs of fish per surface acre of Farmingpond are grown. The pounds grown per surface acre must be kept low to reduce the chance of low oxygen conditions.
Other systems for growing catfish are being developed. Currently these systems are recommended only for those willing to accept a higher level of risk, or those planning only a small scale operation. Raceways are tanks or channels in which large volumes of flowing water supply oxygen and carry away wastes, allowing fish to be produced very densely. Given ideal water temperatures, they still use about 4 times as much water to raise catfish as ponds. Recirculating systems filter and recycle water allowing fish to be grown year round indoors where growing temperatures can be maintained. Potential for fish kills in these systems is high due to unreliable filtration systems.