Although fish farming may seem like a brand new idea, it really is not. Decades of work by farmers and researchers have led to the development of proven facilities for growing fish. As a new fish farmer, you should keep things simple by sticking closely to these tried and proven designs.
Control your urge to invent until you have several years experience in fish farming and fully understand all the reasons why things are done certain ways. The great majority of aquaculture products in the South are produced in levee and watershed ponds.
Other production facilities, including cages, raceways, flow through tanks and recirculating systems, have not been as widely successful for a variety of reasons.
Levee ponds:
Are standing water impoundments built by excavating the pond area to a shallow depth and using the soil obtained to build a perimeter of levees or dikes. The advantages of levee ponds include the ability to harvest by seine without draining and the availability of oxygen all the way to the bottom of the pond.
Disadvantages include relatively high construction costs and the need for a site with a slope of less than 5 percent, soil clay content of at least 20 percent and wells or other reliable water sources. Occasionally, a fish farmer will choose a site with a shallow water table and excavate down into it. This should not be done because management of such a pond is difficult.
Levee ponds may not be fascinating, but they are state of the art when it comes to reliable, economical production of catfish and most other warm water finfish. Crawfish are produced in much shallower levee pond structures.
Watershed ponds:
Are standing water impoundments built by damming ravines or small valleys. From 5 to 30 acres of watershed is needed to supply the water for 1 surface acre of pond. Advantages of watershed ponds include lower construction costs than levee ponds and the ability to make use of steeper sites.
Disadvantages include the inability to refill ponds at will and lack of oxygen at greater depths, which can lead to fish kills if a turnover occurs.
Cages are floating enclosures:
in which fish are grown and fed a complete feed. The main advantage of cages is that fish are cultured in existing water bodies that would otherwise be impractical to harvest. Main disadvantages are quick spread of disease and greater vulnerability to theft, disturbance and moderately low oxygen levels.
Raceways and flow through tanks:
Are long channels or tanks through which fresh water flows continuously and is then discarded. Main advantages of raceways and flow through tanks are ease of handling and harvesting fish and control of waste buildup by flushing.
The main disadvantage is the shortage of sites having abundant water of the right temperature, that is artesian water or water available without excessive pumping costs. Groundwater in the South is generally suitable for cold water fish such as trout, but too cold for warm water species such as catfish. Heating water for raceways is prohibitively expensive.
Recirculating systems are tank systems in which water is filtered and reused. Filtration is conducted by large beds of bacteria, After I got into it, I realized the producers I visited early on were not as dumb as I had thought and I was not as smart.
known as biofilters. Main advantages of recirculating systems are that ideal growing temperatures can be maintained year-round and they can be located anywhere. Main disadvantages are lack of reliability, high production costs and need for constant attention.
Biofilters can be killed by chemicals that are used for disease treatments. They also can die unexpectedly without any apparent reason. More research and development work appears necessary before recirculating systems will be economical for most applications.
At present these systems are being used successfully in some hatchery systems and for broodstock conditioning and production of very high value species.
Location is everything:
Much time, effort and money have been wasted trying to force fish farms to fit in impractical locations. First and foremost, a fish farm needs abundant, good quality water. To raise just 1,000 pounds of catfish requires about 244,000 gallons (0.75 acre-feet) of water.
This is in a typical levee pond that is drained once every 5 to 10 years. Raising the same amount of catfish in a raceway requires an enormous amount of water is roughly 65 times as much as in a levee pond!
Underground water from wells and springs is preferred for fish farming because it is free of wild fish and parasites. Some fish farms do use water from lakes and creeks but problems with fish parasites and invasion by trash fish are a constant battle. Surface waters also carry the threat of random contamination by pesticides or other harmful chemicals.
Some ground and surface waters are totally unsuitable for fish farming. The water source should be tested before purchasing property or breaking ground for construction.
The county Extension agent or aquaculture Extension specialist can assist in determining how best to test the suitability of water for fish farming.
Suitable soils and slopes are vital for the proper, economical construction of ponds of the type used to produce most aquaculture products in the South. To hold water, soils generally need to have 20 percent or more clay content and be free of rock outcroppings, sand layers and other causes of excessive seepage.
Ponds built where soils do not hold water well often must be abandoned because corrective measures are costly. Levee ponds generally are built only in areas with less than 5 percent slope; about 1/2 percent is ideal. Areas with more than 5 percent slope are generally better suited for watershed type ponds.
SRAC Publication 102 has more information on watershed ponds. The county Natural Resources Conservation Service office can assist in evaluating the suitability of a site for pond construction.
Raceways and other production facilities are less dependent on soils and slopes. Laws and regulations can prohibit fish farms on certain sites. A site classified as a wetland usually cannot be developed. Feeding of any livestock in the watershed of a municipal water supply lake may be prohibited.
Sites close to public waters may not be feasible for fish farms because of concerns about escape of fish or discharge of water. Contact a county Extension agent or aquaculture Extension specialist for a list of agencies involved in permitting fish farms. Obviously, it is best to investigate possible restrictions and have permits in hand before making a major investment in a site.
Author:
Marley Beem
