Freshwater fish culture in the United States is a popular and fast growing business. Fish are reared for three main purposes: 1) for stocking public and private waters to support commercial and sport fishing or to be used as bait to catch sport and commercial species, 2) for marketing directly to the consumer for food, and 3) for home aquariums or private fish ponds for ornamentation and pleasure.

Rearing fish to augment depleted natural stocks, or to introduce new species into public waters has traditionally represented the greatest expenditure of effort in America. The State of Massachusetts established the first government-owned hatchery in the United States in 1868. It was followed by the States of Connecticut and New York, and in 1871 the federal government established a fish commission to study the decline of native fish stocks and to recommend remedial measures. This commission later became the U.S. Bureau of Fisheries--the predecessor agency of the Bureau of Sport Fisheries and Wildlife, which I represent, and the National Marine Fisheries Service, which employs my colleagues, William N. Shaw, John B. Glude, and Robert D. Wildman. This year then, 1971, marks the centennial year of our federal government's involvement in fish conservation. A series of celebrations and other special events have been held throughout this year to commemorate our centennial year.

The activities of the federal government in the field of fish culture, fishery research, and management have been expanded greatly during the last one hundred years, but they have been outpaced by the individual state governments. As an indication of the relative level of effort by the federal and state governments, it is noted that the federal goverment operates 95 fish hatcheries and funds another 15 that are operated by states, while hatcheries operated by the state governments number about 500. To get a picture of the total U.S. effort in fish culture, one would add more than 2,000 private fish growers to the above list.


Fish produced at hatcheries operated by federal and state agencies are stocked primarily in public waters to improve or maintain sport and commercial fishing. The Bureau of Sport Fisheries and Wildlife and many state agencies also furnish fish, free of charge, for stocking waters owned or controlled by individuals. Much emphasis is on stocking sport fish since fishing is one of the most popular outdoor sports in the United States. In 1970, over 49 million sport fishermen fished in fresh and salt waters (U.S. Bureau of Sport Fisheries and Wildlife, 1971.)

In addition to federal and state hatcheries, there are well over 2,000 commercial hatcheries in the United States. These are divided into three general classes: bait minnow, catfish, and trout hatcheries.

The estimated production of freshwater fish produced in 1965 by all hatcheries in the United States was as follows:

Metric Ton
Federal hatcheries 2,565
State hatcheries 12,684
Commercial hatcheries
Bait minnows 22,650
Catfish and other warmwater fish  13,000
Trout 9,060

Data from federal fish hatcheries show that production costs have been significantly lower in the past 20 yr (Table 1). The total cost of producing a kilogram of trout has decreased about 4% because of better diets, improved feeding practices, and more efficient operations. Feed costs have been reduced sevenfold since the 19th century, when inflation is considered, and have decreased 25% since the advent of pelleted diets. However, the cost of rearing salmon has remained somewhat stable. Current cost figures were not available for state and commercial hatcheries; however, it is believed that their production costs are somewhat similar to costs listed for federal hatcheries.


It has long been the custom in the United States to classify fish hatcheries into two types--extensive, where large water areas are used to supply both the nutritional and environmental needs, and intensive, where the fish are confined in small ponds or tanks, their nutritional needs met by hand feeding, and their environmental needs met by rapid exchanges of water in the pond. By tradition, extensive culture methods have been used to rear warrnwater and cool-water species (temperatures 15°-27°C), while intensive culture has been practiced for the coldwater species (10°-16°C), in the family Salmonidae. This distinction is beginning to disappear however, as improved technology is demonstrating the practicability of rearing such warmwater species as channel catfish, Ictalurus punctatus, and striped bass, Morone saxitilis, by intensive culture methods.

Extensive Fish Culture

The extensive fish culturist, or pondfish culturist as he is more commonly called, is basically an ecologist. His job is to maintain optimum opportunities for fish to spawn and grow under seminatural conditions. He hopes to improve upon nature by increasing the productivity of the pond. High survival rates are achieved by eliminating competition by other fish and by holding cannibalism to a minimum through the prevention of a size spread of the fish in the pond. In order to maintain uniform size, it is essential that the fish spawn at the same time. This is achieved with channel catfish and striped bass by hormone injection. The spawning time of species such as sunfishes, which are allowed to spawn in the pond, is controlled by separating the sexes and holding them in cold water until seasonal water temperatures have reached the desired level.

Attempts are being made to gain greater control over the spawning and survival of even these species. Limited success in this direction has been achieved by placing nylon fiber mats in the ponds to serve as a place for the fish to deposit their eggs. Experiments conducted at the Fish Culture Development Center at Marion, Ala., during the past several seasons, have indicated a promising preference for the use of the mats by the largemouth bass, Micropterus salmoides. After the eggs are deposited, the mats are removed and placed in hatchery tanks where the required care and protection can be given them. This is nothing more than a modern adaptation of the ancient Chinese practice of placing brush mats in known spawning areas to collect carp eggs.

A principal limitation to higher yield of warmwater species in hatcheries has been the problem of providing natural food. To accomplish this, ponds are fertilized. Intensive fertilization can produce enough natural food organisms in static ponds to rear up to 550 kg of fish from a hectare of water in a single season. Supplementary feeding can increase this up to about 2,500 kg. Oxygen limitations in lentic environments prevent higher yields, but aeration devices should prove that higher yields are possible.

Efforts to hand feed largemouth bass have often been discouraging, but work toward this goal continues, and recent reports from the Development Center at Marion, Ala., tell of producing largemouth bass up to 20 cm long by supplemental feeding, with a conversion ratio of 1.4: 1.

Cultural techniques of other species reared at our warmwater hatcheries are described as follows:

Walleye (Stizostedion vitreum vitreum)

The walleye is one of our most valuable freshwater sport fish. It also ranks high in the commercial harvest. In reclaimed lakes, that is lakes in which the entire fish population has been deliberately poisoned out, this species has had the greatest success when stocked as fingerlings 5 cm long.

It has not proved feasible to rear walleyes to maturity under hatchery conditions. Consequently, adult fish must be trapped from the natural environment during the spring spawning run and hand stripped. The eggs are incubated, usually in a jar battery, and the swim-up fry stocked into fertilized rearing ponds. Under the best conditions. 5-cm fingerlings are harvested in about 4 wk.

Muskellunge (Esox masquinongy) and
Northern Pike (E. Lucius)

The muskellunge and northern pike fit a very special niche as efficient predators in shallow lakes. The muskellunge (or muskies for short) is particularly prized as a trophy fish. Both species are reared in a somewhat similar fashion as adult spawners are tranced in the wild and hand stripped. A certain amount of success has been achieved in speeding maturation of female northern pike by injecting dried carp pituitary interperitoneally at a rate of 5 mg/kg of body weight.

Once the eggs have been fertilized and become turgid, they are incubated in jar batteries until hatching and swim-up. The fry are then stocked into fertilized ponds and 5-cm fingerlings are harvested 3-5 wk later. In the case of muskies, the fingerlings are then stocked back into ponds at a reduced rate and fed forage fish until they reach a length of 25-30 cm. At that size the fish are ready to be stocked back into the natural environment and food survival can be expected.

In recent years, limited success has been achieved in rearing muskies in concrete tanks on a diet of forage fish. Indications are that there will be more tank culture of this species in the future.

Bait fishes

Bait fishes are raised in farm ponds, natural lakes, and other still waters devoid of predaceous fish. Some of the more common species of bait fish reared in the United States are goldfish, Carassius auratus, golden shiners, Notemigonus crysoleucas; and fathead minnows, Pimephales promelas. Once ponds are prepared, culture in the simplest form may be undertaken by merely introducing adult breeders. The prolific nature of these fish generally results in a rapid increase of the stock by natural reproduction. Annual yields generally range from 1,300 to 4,500 kg/ha.

For the past 10 yr channel catfish cultivation has rapidly increased in the United States. There are now approximately 24,600 hectares of ponds devoted to the growing of catfish. This can be compared to 100 hectares 10 yr ago. The gross annual value to the farmers in 1971 was approximately $31 million from the 40,800 metric tons produced.

To date, most catfish rearing has been done in large impoundments, many of them operated in rotation with rice farming. More recent entrepreneurs into the catfish farming industry are large corporations which employ professional staffs of engineers, biologists, and business managers. These enterprises are beginning to use intensive culture methods to rear catfish. Production levels of 9 kg/m3 are being realized in circular tanks.

Raceway culture at the Fish Farming Experimental Station which the Bureau of Sport Fisheries and Wildlife operates at Stuttgart, Ark., is producing about 900 kg of catfish per year in 115 m3 of space with a total flow of 35 liters/sec. Water temperature is 28°C. This is far below the potential for this species in light of experimental data which reveal that 9 kg/m3 are routinely held in circular tanks with a diameter of 2 m and with a water flow of 0.3 liters/sec.

Striped Bass, Morone saxatilis

Striped bass culture, like channel catfish, is showing great promise, although the production of this species is still in the development stage. The geographical range of striped bass extends from the St. Lawrence River, Canada, to the large rivers of South Carolina and Georgia along the Atlantic coast and along the Gulf coast from western Florida to Louisiana (Pearson, 1938).

Recent investigations indicate that the only substantial fishery for this species in Florida is in the Apalachicola River, which empties into the Gulf of Mexico.

On the Pacific coast striped bass ranges from southern California to the Columbia River, Oreg. Introduction of this species to the Pacific coast was accomplished with an initial stocking of 133 yearling fish in San Francisco Bay in 1879 (Mason, 1882). These fish were seined from the Navesink River, N.J., and transported to California by train.

By 1899 the commercial catch of striped bass was 599 metric tons and by 1915 it had risen to 808 metric tons (Raney et al., 1952).

The establishment of landlocked striped bass populations in several inland reservoirs has generated considerable enthusiasm in regard to the future potential of this species. Using striped bass on a put, grow, and take basis could prove to be a desirable management technique for large freshwater impoundments. In addition to its acceptance as a superb game and table fish, the striped bass also exhibits the ability to function as a biological control for gizzard shad, Dorosoma cepedianum.

The ability to produce millions of striped bass fry through hormone induced spawning is now a reality (Stevens, 1966). This accomplishment has resulted in major attempts to establish striped bass populations with large-scale fry plantings. A final evaluation of the success of these programs is not available at this time; however, it is the general consensus that predation will prevent the establishment of desirable populations with this type of introduction. The alternative is to introduce fingerlings (6-15 cm) instead of fry. At least six states in the southern United States have embarked on fingerling rearing programs.

Production at federal hatcheries increased from 90,000 fingerlings in 1966 to 1,500,000 in 1970.

Intensive Fish Culture

Some of the more common species of fish reared by intensive culture method are: rainbow trout, Salmo gairdneri; brook trout, Salvelinus fontinalis; brown trout, Salmo trutta; lake trout, Salvelinus namaycush; golden trout, Salmo aguabonita; cutthroat trout, S. clarki; coho salmon, Oncorhynchus kisutch; chum salmon, O. keta; chinook salmon, O. tshawytscha; kokanee or sockeye salmon, O. nerka; and Atlantic salmon, Salmo salar.

One of the basic advances in trout and salmon rearing is in the area of nutrition. Fish diets are now compounded as carefully and scientifically as diets for domestic animals. The basic nutritional needs of most species of trout and salmon have been defined by such workers as Phillips (1970) and Halver (1970), and diets are formulated to meet these needs. Proximate analysis of typical trout and salmon diets are as follows:

Starter diets
up to
8 weeks old
Grower diets
8 weeks to
Protein 48.4 42.9
Fat 13.2 9.5
Moisture 4.1 6.0
Ash 10.5 10.4
Fiber 3.9 4.1
NFE1 19.8 27.1
Available energy:
Kcal/kg 3,315 3,315
Cost/kg $0.31 $0.31
1 NFE = nitrogen free extract.

Mechanical fish feeders are coming into widespread use and are taking over the role of feeding the precise quantities of feed at prescribed intervals. The more advanced of these devices monitors water fish size, and adjusts the daily

Where the pondfish culturist is basically an ecologist, the trout and salmon culturist is a physiologist He must know the requirements for space, for the physical and chemical components of the water, and for the nutritional requirements of the fish. Through careful control of these factors, each kilogram of trout or salmon produced may

Growth rates can be calculated with utmost accuracy. Haskell (1959) concluded that the increase in length of trout up to 25 cm in size is at a constant rate. He developed a "temperature unit" theory in which he states that the growth rate can be predicted for any temperature between 3.7° and 15.6°C. We have found it practical to restate Haskell's hypothesis to include 0°C as the zero point for growth and consider it to be a straight line relationship when plotted against time up to 15°C. This has proven a useful tool in projecting growth rates and forecasting the time when the fish will reach a given length.

Fish densities in trout and salmon rearing ponds are not as critical as the quality and quantity of the water flowing through the unit. Ample exchanges of water between 0° and 21°C., free of toxic metals such as zinc, copper, and manganese and from excessive levels of such gases as nitrogen, are essential. Oxygen levels must be maintained above 5 ppm throughout the tank, and ammonia should not exceed 1 ppm for long periods of time. If these water quality criteria are met, most salmonids can be reared at densities exceeding 50 kg/M3.

The raceway, a linear pond whose length is approximately 10 times its width, has been the most popular type of rearing unit for salmonids in the United States up to this time. Second in popularity has been the circular pond. Many other types of ponds have been tried, but have not been widely adopted. In 1958 Burrows and Combs at Longview, Wash., developed a circulating pond that is being widely copied in the northwestern United States. This pond is rectangular in shape, but employs turning vanes to cause the water to flow in a circular pattern. The merits of this pond are its higher water velocities and thorough circulation which give good distribution of feed and render the pond virtually self cleaning. The increased velocities improve stamina and result in better survival of the fish following stocking. Water supplies, both entering and leaving a fish pond, must be monitored for their chemical content. Sufficient oxygen must be supplied by the incoming water to permit the fish to use the food. The relationship between food eaten and the oxygen required is so constant that many fish culturists calculate the oxygen content of the water entering a pond as a means of determining the carrying capacity. Investigations indicate that 100 g of oxygen are required to metabolize 450 g of trout pellets (1,200 calories) (Willoughby, 1968). This 1.4:5 ratio should hold constant over the temperature range of 4°-16°C.

While oxygen is usually the first limiting factor in the hatchery environment, it is not the only one. As oxygen is used to break down foods for energy and growth, by-products are formed. Prominent among these are carbon dioxide and ammonia. Carbon dioxide poses few problems. Ammonia, however, is another matter, as it is very difficult to remove by mechanical means. Thus, when water is reused from one fishpond to another, it can be aerated to renew its oxygen content but ammonia continues to accumulate and soon reaches toxic levels.

A recent development which has revolutionized fish culture in the United States is the use of bacterial filters, which convert free ammonia to more tolerable nitrates. This development has opened up possibilities for a tenfold increase in the quantity of fish that can be reared in a given water supply. This reconditioning system makes it possible to reduce the quantity of freshwater by as much as 95%.

The Dworshak National Fish Hatchery, Ahsahka, Idaho, utilizes a water reuse system for a part of its ponds. This hatchery began operation in 1968. There are 84 circulating ponds, 25 of which operate on the water reuse system. In this system approximately 10% of the water used in the ponds is added as fresh water after being filtered, disinfected, and either cooled or heated. The water goes through aerators for oxygenation and is supplied at the rate of 27 liters/sec to each pond. When water returns from the ponds, it goes through biological filters where the pH is buffered and ammonia oxidizes to harmless nitrates.

The hatchery was designed and built to replace the spawning and nursery areas for the steelhead trout which will be lost by the construction of the Dworshak Dam. In addition to the rearing of steelhead trout for release into the north fork of the Clearwater River, this station is also participating in the management of the reservoir above the dam. At the present time, the hatchery is rearing catchable size rainbow trout for stocking the reservoir. In addition, there is a limited number of cutthroat trout on hand which will be used for brood stock as a source of eggs for future stocking programs. In addition to these, it is expected that this hatchery will also supply kokanee salmon for the reservoir.

The first year's operation of the Dworshak hatchery started with the collection of eggs from trout transported to the hatchery from the trap at the dam site during the period of October 1968-May 1969. The fish reared in the untreated water for 2 yr from the 1969 brood year were released in the spring of 1971. At the same time, the 1970 brood year fish reared in the controlled environment of the reuse system were also released. The controlled environment of the reuse system made it possible to rear fish to migrating size (17 cm) in 1 yr instead of the 2-yr growing period that is required when the untreated water is used.


In 1968, the federal government of the United States imposed regulations requiring that salmonid fish and eggs imported into the country be free of whirling disease, caused by the protozoan Myxosoma cerebralis, and viral hemmorrhagic septicemia. The regulation is intended to protect the nation's fishery resources from further introduction of these two fish diseases. It may also serve as a model for adoption by other countries similarly concerned about protecting their own resources. This regulation is included in Title 50, Code of Federal Regulations.

Increased traffic in fish and eggs has spread the virus disease, infectious pancreatic necrosis, in 10 yr from the northeastern section of the country into the trout and salmon producing areas of the West.

The detection of this virus cannot be accomplished by border inspections; consequently, control had to be effected at the originating hatchery. Several states now require that eggs or fish entering the state be accompanied by a certificate of health. But separate actions by the states can only be partially successful, and to effect a coordinated nation-wide program, federal legislation has been introduced in the Congress. If passed, the bill will regulate the interstate and foreign commerce of fish for purposes of disease control.


Fish hatcheries in the United States utilize many diversified types of distribution equipment from 40-liter cans to elaborate tanks equipped with aeration devices and oxygen equipment. However, most hatcheries today generally use truck mounted distribution tanks. Hauling capacity is governed by volume of water in the tanks, design of tank, auxiliary equipment used, and size and species of fish being hauled. Various materials such as wood, plywood, fiber glass, steel, and aluminum are used for construction of tanks. Fiber glass-plywood tanks are becoming very popular because of such advantages as lightweight, low cost, good insulation, and strength. Insulated units, having recirculating water systems and an oxygen supply, can be used to haul loads in ratios (unit weights of fish to equal unit weight of water) of 1.1:5 for trout and 1.2:4 for channel catfish, Maloy (1966).

There are reports of varying degrees of success in increasing hauling ratios by use of sedative drugs and buffer agents. Phillips and Brockway (19S4) found that starvation of fish before shipment and the maintaining of low water temperatures were more effective than the addition of chemicals.

Maxwell and Thoesen (1965) reported on the successful hauling of large quantities of rainbow trout and largemouth bass fingerlings by airplanes equipped with water tanks. Sealed plastic containers, 2 mil and thicker--packed in insulated outer cartons, partially filled with water, and inflated with oxygen--are used successfully by many hatcheries for surface and air transportation of fish. A typical shipment is 50,000 bass fry in 3.8 liters of water for a period of 48 hr.

A recent development in the field of fish transportation is the "fish pump." The fish pump is a modified fruit pump which was initially used to transfer vegetables, fruit, dead fish, and seafood. The pump is especially designed to eliminate sharp edges in the pump body and to allow unobstructed passage of water and produce. The water serves as a cushioning agent.

The pump comes in two diameters, 12 and 15 cm. The 12-cm size is used for fish up to 15 cm in length and the 15-cm size handles fish up to 47 cm in length. The California Department of Fish and Game tested this pump and found that 900 kg of trout could be loaded into a tank truck in 6 min with slight loss of time due to crowding racks. Other tests indicate that 200 kg of trout per minute can be loaded onto trucks from concrete raceways.

In addition to loading distribution trucks and transferring fish between ponds, the pump can be attached to a grading device. With this device about 200 kg of fish per minute can be sorted by size.


The federal government operates three in-service training schools for training fish culturists. These schools are located in Spearfish, S.Dak.; Marion, Ala.; and Leetown, W. Va. They were established to provide essential technical training in the field of fish hatchery management. Operation of the schools is oriented to the activities of the Bureau of Sport Fisheries and Wildlife and includes such topics as nutrition, pathology and disease control, fish-cultural development, and general fish hatchery management. In addition, strong emphasis is placed on the use of hatchery fish in managing open waters.

Although the primary goal is to provide trained fish culturists for the National Fish Hatchery System, there has been increased interest in recent years from state and foreign agencies in sending trainees to the schools. The trainees may already have a broad academic background in biology, but the art of application must be learned through practice. The training schools serve as a link between the academic world and the actual hatchery operation. In fact, T. Sana, a native of Japan, completed our fish disease course at the Leetown National Fish Hatchery last year.


A totally different approach to intensive fish culture is the Tehama-Colusa multipurpose water diversion project and spawning channel in California. Built to divert water for irrigation purposes from the Sacramento River, the upper 5.5 km of this canal will function as a spawning channel for 60,000 chinook salmon.

Access to the spawning channel will be controlled to allow optimum numbers to lay their eggs at one time. The eggs will incubate in the canal, and the resulting young fish will live and be fed there until they are ready to migrate. to sea.

When the spawning channel reaches full capacity. up to 60 million chinook salmon will begin life in this man-made habitat. They will migrate to the ocean to live and grow. Three to seven years later they will return to the Sacramento River as vigorous fighting game fish and also valuable, nutritious food. Some individuals may weigh 30 kg, and where 1 kg of fish migrated to sea from the spawning channel, 50 kg will return. Most of the returning fish will be captured by either sport or commercial fishermen before they reach Tehama-Colusa, but sufficient numbers will reach the canal to assure perpetuation of the run.

Operation of the spawning channel is both an engineering and a fish cultural challenge. The engineering challenge will be in operating the mammoth traveling bridge which will service the canal. The bridge will span the canal, and travel its length via motorized carriages running on rails along the sides of the canal. It will serve as a working platform from which biologists and engineers can manipulate both the fish and their environment for optimum production. An underwater viewing chamber will be suspended from the bridge to permit the observation of the movements and behavior of the fish. Elaborate gravel cleaning devices will flush deposited silt from the channel after each spawning season. Young fish will be sorted, counted, and representative numbers marked as a means of evaluating the contribution to the Pacific salmon fishery.

These and other changes that have taken place during the last few years in fish hatcheries, reflect an emerging scientific approach to the ancient art of fish culture.



BURROWS, R. E.. and H. H. CHENOWETH. BURROWS, R. E. and B. D. COMBS. DAVIS, H. S. HAGEN, W., and J. P. O CONNOR. HALVER, J. E. HASKELL, D. C. MALOY, D. R. MASON, H. W. MAXWELL, J. M., and R. W. THOESEN. PEARSON, J. C. PHILLIPS, A. M., JR. PHILLIPS, A. M., JR., and D. R. BROCKWAY. RANEY, E. C., E. F. TRESSELT, E. H. HOLLIS, V. D. VLADYKOV, and D. H. WALLACE. SPEECE, R. E. STEVENS, R. E. TUNISON, A. V. WHITE, J. T. (editor). WILLOUGHBY, H. 1 Chief. Division of Fish Hatcheries. Bureau of Sport Fisheries and Wildlife. U.S. Department of the Interior. Washington. D.C. 20240: present address: Bureau of Sport Fisheries and Wildlife, U.S. Department of the Interior. P.O. Box 25486. Denver. CO 80225 .

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