Managing a Fish Farm

By George W. Klontz.

Food fish farms in America come in many sizes and shapes. Although no two are alike in layout, there are major similarities: all of course have fish, utilize water, have ponds to retain the water, use either natural or commercially prepared feed, and incorporate some degree of management.

Each of these major categories has several physical, chemical, and biological factors which can, and often do, affect productivity of the fish farm. These factors must be considered by the fish farmer for the farm to be economically profitable.

Nutritional, environmental, and behavioral requirements of the fish are the most important factors to be considered. Fish are perhaps the most diverse of all creatures. There are fish which live in waters of nearly 100 F (46 C), others live in waters of nearly 32 (0 C). Each species has its preferred temperature; its growth potential will be reduced if required to live in waters outside its temperature optimum.

Dietary preferences of fish range from those which are herbivores (plant eaters) to those which are carnivores (meat eaters). Some fish can utilize both plant and animal proteins. These are omnivores. Behavioral tendencies of fish range from those which are sedentary and territorial to those that roam in schools.

It is essential that these major insights about fish be taken into account when one manages a fish farm. All the other factors of pond style, water quality, and nutritional quality (and quantity) are predicated on meeting needs of the fish.

Product Definition

Managing a fish farm can be very complex or relatively simple, depending upon the nature of the farm. No matter what the degree of management is, the process begins at a common point the product definition. That is, what is to be produced in terms of size, quality, number, and season.

Good management embodies matching fish-water-pond interactions with the product definition. The nutritional component is like the throttle on an automobile. The more the fish are fed, up to a point, the faster they will grow.

Product definition is established first, then the management process is initiated with the purchase of eggs or fry. This stage in life of the fish is fraught with all sorts of disaster potentials.

Dissolved oxygen and ammonia levels can become critical quite rapidly. Also, uneaten feed and accumulated fecal solids can reach dangerous levels in a matter of hours. Any of these overloads is deadly for the fish and quite expensive for the farmer.

The usual mortality occurring from the fertilized egg through a 2-inch fish is 15 to 20 percent, just from improper management practices.

Economics of producing food fish dictate the need for sound management practices. Perhaps the single most inadequately applied practice is record keeping. This is really the drudge work of fish farming. Still, the farmer must know how many fish of what size are in the pond in order to feed them appropriately and economically. In addition, the farmer must know how rapidly these fish are growing in order to determine at some point in the future when carrying capacity of the system will be exceeded.

Computer Role

Keeping records and predicting when the fish will be a certain size is done with computers, the most recent development to assist the fish farmer. One standard personal computer can store and evaluate the collected data from virtually any fish farm. Besides saving time for the farmer, the computer also can reduce day-to-day mortality by providing a warning that a pond is near the danger point for the fish.

Continuing education is another frequently overlooked aspect of fish farm management. This aspect can take many forms: reading one or more of the many fish farming magazines, attending fish farming association meetings and conventions, attending short courses. They all cost money and take time, but there is no easy way to keep up to date on new technological developments in fish farming.

George W Klontz is Professor of Fishery Resources, University of Idaho, Moscow.