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Feeling Cagey About Fish Culture: How to Raise Fish in Cages

1/22/2014 10:42:00 AM

Tags: aquaculture, raising fish, ponds, Louisiana, Kenneth Rust

Cages Trout Robinson

In 1994, as a new, young salesman for Aquacenter, a fish farm supply company in Mississippi, I was fresh out of Louisiana State University with little practical training in aquaculture, but eager to contribute where I could. I received a couple of days of training, a truck, an old customer list on dot-matrix paper, a credit card, a case of catalogs, and a territory of small-scale, scattered fish farms.  That is when the real education started for me, as I traveled over southern Louisiana, Mississippi, and Alabama.

Since some of the items we offered, like aerators, were heavy and expensive to ship, I would incorporate delivery into some of my sales visits. One of my first deliveries was an aerator to a catfish farm in Lucedale, Miss., that raised the fish in cages.  The farm was about three-rabbit-trails-into-the middle-of-nowhere, but I found it with the help of handwritten directions from the secretary. There were no affordable GPS, and cell phones then. I pulled down the dirt drive past two, one-acre ponds, each with a small dock and 4 to 6 floating cages surrounding each dock.

Mr. Simmons came out to meet me on the porch of his log cabin home and we inspected his new aerator.  I asked him about his operation, partially because I couldn’t imagine how the fish went to market.  Turns out he not only raised fish in cages, but he successfully sold the concept to the local community.  People in Mississippi eat catfish, and before the concept of buying local, and knowing the farmer was trending, it worked for Mr. Simmons. He invited the public, through bulletin board posts and small signs, to the farm for harvest days. He informed me, “That Saturday, when we have a sale, they are all lined up down the road with ice chests.” He fed the fish a commercial pelleted ration and worked to keep good water quality in the ponds by flushing with well water. He claimed that the approach, in addition to the catfish never coming in contact with the bottom mud, gave a better tasting catfish, avoiding some of the muddy flavor that can occasionally occur with catfish.  Mr. Simmons’ problem was not how to get the fish to market, but how to increase production to meet local demand.

He had experienced a crash in oxygen levels, resulting in the loss of some of his stock, and wanted to ensure that he didn’t lose any more fish that way. I assured him that aeration was a good investment and I gave him one piece of useful advice: Break up the well water as it enters the pond either by splashing or spraying through a nozzle. Well water is predictably clean but is low in oxygen and high in carbon dioxide.  While the well water was diluting the waste products in the pond, it was aggravating his low-oxygen conditions.

Advantages of Fish Cage Culture

Commercial pond culture of fish requires special construction and harvesting equipment. Cage culture allows fish production in your pond without pond renovation, the investment in large harvesting equipment, or draining for harvest. Some other advantages of cage culture provides are:

Small, manageable crops of fish.

Partial harvests of fish, only removing what you need for a sale or dinner.

Healthy protein for your family or for market.

Easy inspection of fish during culture.

So if you have a small pond on your property and you are interested in culturing a crop of fish, cage culture may be for you. Let’s talk basics. 

Consider Your Market

My professor at LSU, Dr. James Avault , always told me not to grow a fish unless you have a market. That can be your dinner table or someone else’s but you should know its destination after harvest to design your culture plan. What species? How many fish to harvest at once? Who will buy them? How big will each fish be at harvest to make you or your customers happy?

Fish Species Suitable For Cage Culture

Channel catfish, tilapia, and rainbow trout can all be cultured in cages.  Trout would be suitable for cooler waters (below 65 degrees F), while channel catfish and tilapia would be suitable for warmer climates (above 65 degrees F during the growing season).

Tilapia and catfish can be cultured together.  Tilapia will feed on algae in the water column and gain additional weight from this input.  Tilapia are an exotic species and you will need to check local regulations early in the planning stages to consider if this species in an option in your state.

Density

In addition to a good return on your investment, high stocking density in cages helps manage aggressive behavior with catfish in particular.

Density in a 4 x 4  cylindrical cage, optimum growth temperatures, and lethal temperatures for species:

400 trout fingerlings 6-8 or 8-10 inches  

Best growth 55-65 F

Stress/death above 70 F

250-400 catfish fingerlings 6-8 inches                

Best growth 80-85 F

 

250-400 tilapia fingerlings 6 inches or larger   

Best growth 80-90 F

Stress/death below 55 F

Up to 1,500 pounds of harvestable fish, or 4 fully stocked cages, can be cultured in a 1-acre pond without using mechanical aeration. To create better chances of success, start with no more than two cages, or 750 pounds, as a target harvest for a one-acre pond. This will allow you to determine what a sustainable load on your pond is, and how the pond’s water quality will respond to the increased input and productivity.

Placement of Fish Cages

Catfish cages Photo Dr. Mike Masser

Several factors should determine placement of your cages. Aeration and circulation is important for good water quality. Place your cage in at least 6 feet of water with no aquatic plant beds underneath and no overhanging tree limbs. Choose a location so that prevailing winds push water through the cage. If you are going to employ mechanical aeration, locate the cages near a power source.

You will need to access the cages daily to feed your fish. Will you do this from a boat or pier?

Keep cages away from farm animals, pets and human activity that can disturb them. Fish can stress from too much activity and this leads to poor weight gain and possibly stress-related disease.

What Will I Feed My fish?

Commercially produced rations provide a fully balanced diet for your fish, designed for the species you decide to stock. This is the first option. Since fish are confined to the cage, they don’t have the option of foraging for other food in your pond to balance their diet, and good nutrition is essential to good health and good growth. The exception is tilapia, which are able to filter feed and harvest the plankton (free-floating algae) in the water (available algae and good circulation are key).

As a supplemental feeding method for ponds, and possibly cages, there are bug-harvesting machines on the market. There are a couple of designs, but basically light attracts bugs to the machine, and a mechanical whip similar to a weed trimmer, knocks them down for fish to consume. The insects are high in protein and readily available near ponds. There may be some innovations necessary to employ this while keeping a protective cover on the cage, but I think that it would be a good way to supplement the fishes’ diet. There are also people that supplement fish diets with cultured worms, and larvae, as well as composted agricultural products like rice bran. I am all in favor of innovation and sustainability, but when choosing a diet, keep in mind that the fish are confined and must have a complete diet.

Next time, I want to continue on this subject with thoughts and information on cage construction, aeration, and another character from the cage culture industry.



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