Fish Farm with Cages!

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FEEDING

Fish in cages have very limited access to natural food. The cage culturist, then, is responsible for providing a diet which is both quantitatively and nutritionally complete.

Most American fish culture is based on commercial processed feeds. These are somewhat expensive, and there are ecological arguments against using them (they're made primarily from fish meal, cultivated grains, and petroleum-synthesized vitamins ... products that could certainly be put to more appropriate uses). However, the rations are both effective and convenient, and beginning cage culturists have enough to learn without trying to create their own feeding schemes

The majority of ready-made fish food is tailored to the requirements of either channel catfish or rainbow trout—our two major conventional aquaculture crops -and will thus be only approxi mately suited to other species. Such feeds often lack certain trace nutrients, as well, since pondraised fish (for which the foods were created) are expected to gather minor quantities of natural organisms. However, some manufacturers do offer special cage culture feeds that are nutritionally complete. (You may not need this more expensive fish food, though . . . if you can supply some of the natural supplements I'll discuss below.)

The other characteristic necessary in any feed used in cages is that it float. Sinking rations will be largely lost through the bottom mesh.

Commercial feeds range in size from meal to 3/16-inch pellets. You can pretty well gauge the size you'll need to buy by the mouths of your fish. Since that size will change as your stock grows—and because the feed doesn't store well—you should always buy the smallest convenient quantity at one time. (And keep those rations tightly covered.)

The best time to feed is usually at dawn ... and later in the morning or at dusk are second choices. As a rule of thumb, you'll want to give 3% of the total body weight of your fish at each feeding, and feed them six days a week. And how do you determine the total weight of your fish? Simply catch and weigh a sample periodically, and calculate the total group's weight ... using this information and the number of fish in the cage.

I strongly recommend that you employ this sampling method during your first season. In subsequent years, you may develop enough of a feel for feeding to skip the sampling and successfully raise fish by simply giving them the amount they'll consume in a half-hour (or one hour, if you're raising carp).

To gain some idea of the kind of feeding schedule you'll have, make a few calculations using the "end point" method. To illustrate how this works, let's suppose you begin with 200 bullhead fingerlings that, all together, weigh 2-1/2 pounds. Now, assume that you want to raise them to an average of 1/2 pound each, thus yielding 100 pounds of fish. Using the 3% weight-a-day feeding rule, you would then give them 0.03 X 2.5 = 0.075 pounds of ration the first day. Furthermore, on the last day before harvest, you'd be feeding 0.03 X 100 = 3 pounds of feed.

If you have some idea of when that harvest date will- occur-a good time is just after the date your water temperature falls below that needed for optimum growthyou can then count the number of feeding days between stocking and harvest and calculate an approximate weekly feed allotment that gradually increases from 0.075 to 3 pounds a day. Be sure, however, to allow for the fact that fish put on weight most rapidly at first, and slow down some as they grow.

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