This uncomplicated technique is most commonly used in North America by commercial fish farmers, but — as years of successful experimentation at the New Alchemy Institute farm in Hatchville, Massachusetts have shown — it could be employed by any individual who has access to an appropriate natural or artificial pond or lake, says a recent article in Mother Earth News.
Furthermore, the number of fish that can be produced in a single floating cage is astonishing. The current records for rainbow trout, channel catfish, and common carp—three oft-reared species—are all approximately 15.6 pounds per cubic foot. Therefore, a cage that's only three feet on a side (totaling 27 cubic feet) could conceivably be used to raise over 400 pounds of fish! And in more practical terms, even a first-time grower should be able to achieve harvests of nearly four pounds per cubic foot ... producing 100 pounds of fish in a 27-cubic-foot cage.
How it WorksTo understand just how fantastic that rate of production is, the articles suggests you imagine a 3' X 3' X 3' hole—filled with water—in your back yard. Then visualise 100 pounds of fish swimming around in it. That's the "beginner's yield" we're talking about!
Most people are aware that actually trying to produce fish in a small hole would create serious problems long before that 100-pound harvest could be achieved primarily because the creatures' wastes— along with any uneaten feed—would soon, drastically pollute the water. If such contamination didn't kill the fish outright, it would certainly retard their growth.
Of course, improving water quality and stock growth by using some combination of circulation, aeration, and filtration technologies could boost production. However, cage culture, solves the problem of pollution in a small space because of the constant exchange of water between the screen-walled cage and the larger body of water in which it floats. Even landlocked, supposedly stagnant ponds have some natural circulation as a result of wind and convection currents. The major source of water movement in a cage is often a "natural pump" a result of the swimming and breathing of the fish themselves! And, since the stock's containers are normally floated in the upper layer of water that's at least 6 feet deep—where there likely are relatively few other fish and little organic decomposition—the incoming fluid is usually clean and rich in oxygen.
Why Use Cage CultureThe outstanding advantage of cage culture is that it permits "fish gardening" in bodies of water that aren't suitable for more intensive aquaculture (in which large nets are used to harvest the crop). Such locations include the following:
- Public (or large private) waters
- Multipurpose ponds
- Ponds with more than one owner
- Very deep pond
- Brushy ponds
Fish TypesAlthough most fishes probably can be raised in cages, experience to date suggests that, if you're more interested in production than experimentation, you should select from the seven varieties listed below:
- Channel catfish (Ictalurus punctatus)
- American eels
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