2000 Annual Report for FS00-122
Using Caged Filter-Feeding Fish to Increase Production and Profits from Fertile Catfish Ponds
Summary
In Alabama, channel catfish are produced in static water ponds that are drained once every eight to ten years. The water becomes eutrophic with natural pond production (plankton) fertilized with nutrient byproducts of feed and fish wastes. Catfish make little use of plankton because most of it is microscopic and catfish do not possess the feeding apparatus to filter it from the water. The plankton may reach such high concentrations that they suddenly die, usually because of poorly understood dynamics. When the oxygen producing plankton die, producers have a crisis with low dissolved oxygen that could result in major fish mortality. Many producers routinely apply algaecides to reduce plankton populations and the chance of die-offs. Algaecides are costly and may have long term detrimental effects on the pond ecosystem.
Plankton are excellent nutrition for fish equipped to filter them from the water. An alternative technique to manage excessive plankton, therefore, is to convert plankton into another fish product that could be marketed. If successful, this technique could reduce the need for chemical algaecides while increasing farm income from harvested fish. Attempts to co-stock filter feeding fish in catfish ponds to consume plankton have been frustrated by other problems.. Producers may be assessed a fee by processors for separating the filter fish from catfish, and some seining crews refuse to harvest ponds containing large carps. Lastly, some filter feeding fish have no obvious market value.
This producer will put filter feeder fish in cages where they remain separated from catfish, don’t compete for feed, and may easily be removed at harvest. He will evaluate the growth and production of Tilapia in cages placed near aerators where the water moves. The Tilapia is a well-known filter feeding fish, tolerant of water quality extremes encountered in catfish ponds, and highly marketable. Tilapia grow well in cages on a high quality diet, but their production potential as a filter feeder in commercial catfish ponds has not been evaluated and published.