The first harvests of fish that occurred with any degree of regularity in ponds probably were made as a result of entirely fortuitous circumstances. In all likelihood the ponds were naturally occurring bodies of water including those 1) left as an aftermath of flood conditions, 2) resulting from seasonal recessions in lake levels which isolated shallow embayments, and 3) formed by various geological processes (e.g., oxbows and sinkholes). Later on, ponds used for irrigation, flooded areas such as rice paddies, and other man-made features proved to be sources of fish at certain times of the year. Gradually the realization grew that it would be profitable to build structures for the purpose of providing greater control of both water and fish than is possible under natural or semi-natural conditions. When this occurred, an important step had been taken toward the goal of domestication and intensive cultivation of fishes.
Fish culture is an ancient art that probably was initiated in mainland China and in India several thousand years ago, and in Japan shortly thereafter (Tubb, 1967). A tomb frieze of 2500 B.C. shows that the ancient Egyptians harvested, and perhaps cultured, fishes of the genus Tilapia (Bardach, 1968). Brackish-water fish culture was established in Java between 1400 and 1200 B.C., and in the Philippines several hundred years ago (Tubb, 1967). The Romans practiced fish culture during the centuries immediately before the time of Christ, and the art spread throughout Europe during the Middle Ages, reaching England in the early part of the 16th century (Edminster, 1947). In several countries of Asia and the Far East the abundance of natural supplies of fish rendered fish culture unnecessary, hence it is only within the last century that artificial cultivation of fish in controlled ponds has developed to any significant extent (Tubb, 1967). The history of fish cultural activities in both fresh and brackish waters in the Indo-Pacific region is well summarized by Hora and Pillay (1962). Fish culture was not established in North America until the 19th century, and major emphasis was on production of species of importance to anglers and commercial fishermen until about 25 years ago when culture of food fishes began to develop. Only in comparatively recent years has fish culture been developed in Latin America (Miles, 1967) and in much of Africa (Meschkat, 1967).
Generally speaking, fish production ponds are bodies of water (fresh, brackish, or salt) devoted to the culture of various species of fishes or shellfishes throughout part or all of their life stages prior to harvest. The degree of husbandry exercised varies from virtually none to the most intensive cultural efforts in every phase of production.
Most of the world's fish cultural efforts have been devoted to the production of food, and the rapid increase in world population has greatly stimulated attempts to develop more effective methods of aquaculture and to introduce the practice in protein-deficient areas which have had little or no experience in culturing aquatic organisms.
Not all fish cultural efforts, however, are devoted to the production of commercial fishes. Fish hatcheries and fish farms of all sizes and degrees of complexity are operated also for the benefit of anglers. Fish production related to sport fishing activities probably is developed most highly in North America, but sport fisheries are maintained in numerous other areas of the world. Various members of the family Salmonidae have been introduced as the principal species of interest in many of these places.
The need for hatchery production of sport fishes in the United States is indicated by the fact that in 1965, 59 percent of 21,942,938 ha (54,221,000 a) of cold waters and 42 percent of 11,097,127 ha (27,421,000 a) of warm waters, or a total of 53 percent of the inland fishing waters, required periodic stocking. Furthermore, by the year 2000, it is anticipated that an additional 809,384 ha (2 million a) of cold water and 2,023,472 ha (5 million a) of warm waters will be stocked. At least eight of the 23 coastal states are considering the stocking of marine and additional anadromous fishes, but initial efforts will be confined largely to research to solve major problems associated with the culture of marine species (U.S. Bureau of Sport Fisheries and Wildlife, 1968).
According to stroud and Martin (1968), approximately 1.4 billion fishes of all species and sizes weighing an estimated 9,011,612 kg (19,867,000 lb) were distributed from state and Federal fish cultural stations in 1965. Nearly 1.2 billion of these were warm=water fishes, yet the demand for that year exceeded the supply by 683 million fish (U.S. Bureau of Sport Fisheries and Wildlife, 1968). Planned increases in production of warm=water species should reduce this deficit to about 333 million fishes annually by 1973, where it is expected to remain fairly constant until the year 2000. In 1965 the demand for cold-water fishes exceeded the supply by nearly 14 million fish, and by the year 2000, the deficit will have about tripled despite the fact that production will have doubled by that time. Thus, the tremendous increase anticipated in fishing pressure clearly requires both more efficient use of existing hatcheries and construction of sizeable numbers of new facilities if there is to be any possibility of satisfying the mounting demand for sport fishing.
For untold centuries after its beginning, the culture of fish and other aquatic organisms was carried out largely on a trial-and-error, hit-or-miss basis. Stocking of eggs, fry, larvae, or other early life stages of various organisms was done rather indiscriminately for want of methods for obtaining pure cultures of the desired species.
Organisms detrimental to fish cultural efforts gained access to ponds via the water supply, by access from connecting surface waters, through accidental or deliberate stocking, by incomplete harvest of preceding crops, and in a host of other ways. Until relatively recent years, there was no really satisfactory way 1) to remove all residual fishes from a dewatered pond after harvest if it could not be completely drained and thoroughly dried, 2) to eliminate all fish from undrainable ponds so that no predators or competitors remained to prevent optimum growth and development of newly stocked populations, or 3) to selectively reduce or eliminate certain species or size groups of fishes.
Even though the operational procedures followed by fish producers have improved greatly, many problems remain to be solved. In the United States for example, catfish ponds filled from surface water supplies sometimes become infested with undesirable species including gizzard shad, carp, buffalo, or green sunfish. In addition, it is not uncommon to find small green sunfish mixed in with fingerling catfish that have been produced in contaminated brood ponds. If the scale-fishes are not controlled, their competition for food, space, or oxygen may exert a very detrimental effect on growth and survival of the catfish, to say nothing of the economic loss incurred as the result of introduction of parasites or diseases and the problem of sorting scale-fishes from catfish at harvest. Losses of fingerling catfish through predation may be a very serious problem if they are stocked into ponds containing adult green sunfish or largemouth bass.
Minnow ponds may be subject to many of the above problems, but losses incurred as a result of predation are likely to be even more serious. Furthermore, the presence of many tadpoles and crayfish is especially undesirable in minnow ponds and in ponds of fingerling catfish because of competition for food, the injuries inflicted upon small fish by crayfish when they are crowded together in a seine or catch basin at harvest, and the labor involved in hand sorting to remove unwanted fish, crayfish, and tadpoles. Snails also are detrimental because they are intermediate hosts for several fish parasites, which can cause losses of considerable magnitude. Aquatic insects that prey upon fish fry are highly undesirable in either minnow ponds or channel catfish brood ponds, and must be controlled if large losses of fish are to be avoided.
Occasionally severe disease problems or infestations of parasites make it necessary to destroy the entire fish population of a pond or even all of the fish in an entire hatchery. Examples of such occurrences in the United States are as follows: trout infected with kidney disease, infectious pancreatic necrosis, or whirling disease; channel catfish infected with internal fungus infections (systemic mycosis) and with channel cat-fish virus disease; and smallmouth and largemouth bass infected with bass tapeworms (Proteocephalus ambloplitis).
In some areas of the world fish culturists are faced with the problem of controlling infestations of food fishes by parasites that are dangerous to man. These include tapeworms of the genus Diphyllobothrium, and the liver flukes Haplorchis, Opisthorchis, Metorchis, and related genera (Van Duijn, 1962). Plotnikov (1959) reported a high rate of incidence of the human liver disease, opisthorchosis, in certain areas in Russia, and mentioned that the disease in man has been described in Poland, and in domestic carnivores in Germany, Holland, France, Italy, and Hungary. The adult form of Metagonimus jokogawai is an intestinal parasite of domestic and wild carnivorous animals, birds and man, and the adult form of Clonorchis sinensis, which is endemic in the Far East, is a parasite causing distomatosis of the liver in man (Bykhovskaya-Pavlovskaya and Petrushevskii, 1959). The control of mollusks that are the first intermediate hosts of several parasites is suggested as one of the initial steps to be taken in reducing the incidence of parasitic diseases affecting man.
Warm-water fish culture in some countries of Africa causes concern from the point of view of public health because the ponds may become infested with snails that serve as vectors for schistosomiasis (bilharzia). According to Meschkat (1967), Schistosoma infestations of epidemic character have occurred even in scientifically controlled, fish breeding centers. No molluscicides that are safe to flora, fish, and other fauna in fish ponds have been found. The control of vector snails by stocking malaccophagous fishes has shown promising results, but the method is not widely practiced. Thus, fish culture, fish control, and snail control are closely related problems in parts of Africa.
The control of undesirable organisms is one of the more critical elements determining the success of efforts to produce fish. Prior to the introduction of chemical tools, fish culturists and fish farmers employed many measures in attempting to eliminate a wide variety of vertebrate and invertebrate pests. However, these methods usually fell short of achieving the desired results, and it has been generally recognized that the use of chemicals offers by far the most practical means for 1) prompt control of most parasites and disease organisms, 2) control (in full ponds) of predaceous insects and insect larvae that are not air breathers, 3) eradication of other undesirable invertebrates in undrainable ponds, 4) total removal of fishes prior to stocking, 5) selective removal of unwanted species from stocked ponds, and 6) elimination of fishes from watercourses that are dammed.
Fish culturists who produce fish on a commercial basis in privately owned ponds bear the unrelenting pressure of economic necessity to produce a crop every year and to do it as inexpensively as possible. Thus, in their choice of general toxicants, they quite understandably are more inclined to search out and use almost any chemical that offers the possibility of achieving nearly total control of a broad spectrum of predatory, competitive, and otherwise detrimental forms of life. These forms include fish, predaceous insects and insect larvae, snails, tadpoles, crayfish, leeches, parasites, and pathogenic organisms of many kinds. Even though populations of invertebrate food organisms sometimes are severely reduced by such toxicants, they soon rebound under the intensive care given such ponds provided that no harmful residues persist to hamper their recovery. Ease of application and duration of toxicity are significant factors in the fish farmer's choice of toxicants, but price and the compelling need to avoid toxicants that produce an accumulation of residues in the pond and depress future production might well be of paramount importance. It should be pointed out that another highly important consideration recently has been added for producers of food fishes in some countries -- the requirement that no chemical compounds be used which would leave objectionable residues in the fish at time of harvest.
Fish culturists working in public hatcheries generally have somewhat different needs for toxicants as shown by the following examples: 1) controlled monoculture eliminates the need for selective toxicants; 2) the buildup of harmful organisms often can be controlled by operational procedures that are denied to commercial growers who must keep ponds in almost constant production; 3) the cost factor is not as critically important to managers of public hatcheries as it is to private individuals engaged in the highly competitive area of commercial enterprise; and 4) managers of public hatcheries are not free to apply highly toxic chemicals such as the organophosphates and sodium cyanide under any circumstances. In view of these and other considerations, it is not surprising that commercial fish producers have used many more kinds of toxicants than have other fish culturists.
Fishery managers have many uses for toxicants that are quite unlike those of the two above groups. Some of these are the need to eradicate undesirable fish populations in stream systems above new reservoirs, selective removal of warm-water fishes or predatory species from trout waters, selective control of undesirable species in populations of warm-water fishes, and selective thinning of panfishes or other highly prolific species to restore population balance, improve growth rates, and enhance fishing success. Fishery managers also have problems with toxicant application that are different from those of fish culturists and fish farmers. It is most difficult to obtain good distribution of toxicants in waters that are deep, infested with growths of aquatic weeds, marshy, or in isolated potholes in the basins of impoundments that have been drained. Streams are hard to treat properly because of difficulty in gaining access to small tributaries in remote areas of the headwaters; flows are hard to gauge accurately; springs, seepage areas, and backwaters present special problems; the detoxification of waters at the lower end of the treated area often is necessary, and may be expensive and difficult to accomplish; and the chemical qualities of natural waters tend to be much more variable than those of waters that have been chosen purposely for fish culture. Furthermore, the diversity of species that fish managers have been required to control is nearly as broad as the ichthyofaunal lists of the areas in which management is required. In nearly all fishery management programs, fish are the only target organisms, hence toxicants that do minimal damage to invertebrate populations are greatly to be desired.
It is difficult to categorize toxicants according to their uses, but the following groupings of materials used in ponds are felt to be generally valid: 1) those that are used or have been tested almost entirely for controlling fish include saponin, powdered croton seed, endrin, benzene, turpentine, rotenone, toxaphene, antimycin, copper sulfate, polychlorpinene, sodium sulfite, sodium hydroxide, Dibrom-malathion mixtures, Bayluscide, Thanite, ichthyothereol, callicarpone, other botanical toxins than those given above, and chemicals to manipulate the hydrogen-ion concentration of pond water; 2) those that serve both as piscicides and herbicides are Aqualin and anhydrous ammonia; 3) those employed primarily to control invertebrates and only secondarily to control fish include malathion, Guthion, Baytex, ethyl parathion, thiometon, DDVP, and phosphamidon; 4) compounds used largely as pond sterilants are lime, chlorine, calcium cyanamide, sodium pentachlorophenate, and rosin amine D acetate; and 5) other materials serving two or more of the above purposes include tobacco wastes and sodium cyanide. Without doubt many other substances toxic to fish have been recommended or tested experimentally, but records of such trials either were not prominent in the literature or were not immediately available when this review was being prepared.
The choice of method for applying a chemical is influenced by several factors including the following: formulation and bulk of the toxicant (gas, liquid, paste, powder, granule, crystal, pellet, briquette, or cake); the purpose for which it is applied; size and depth of waters to be treated; chemical characteristics of treated waters; whether the water is flowing or static; physical difficulty of reaching areas to be treated; obstacles that prevent complete distribution and dispersion of the toxicant; toxicity of the chemical to applicator and other non-target organisms; the speed with which the application must be completed; and time of the year when the application must be made.
During the past 40 years or so, there has been an interesting evolution and diversification in the numbers and kinds of toxicants, their formulations, and methods of application. The earliest usage involved naturally produced toxins that were applied by hand (e.g., saponin and rotenone), and such usage will continue to meet certain needs for some time to come. As larger, deeper ponds were treated, gasoline-powered pumps and outboard motors came into use to reduce the amount of time and labor involved. The application of lime to dewatered hatchery ponds also was mechanized by pumping a thin slurry of the material over the exposed bottoms, thus reducing or eliminating the need for laborious scattering of powdered lime by hand.
The use of motorboats greatly facilitates the application of many kinds of toxicants, even in small ponds. Emulsifiable rotenone and slurries of powdered rotenone are dispersed from boats by means of pumps or sprayers, or by pouring the mixtures into the propeller wash of the outboard motor. In any case the motor is used to stir the water vigorously to achieve better dispersion of the toxicant. Weighted sacks of powdered rotenone or weighted hoses discharging rotenone solutions frequently are used in treating areas of deep water.
Solutions of antimycin are introduced by pumps, sprayers, or by spilling into the propeller wash of a boat. Sand-formulated antimycin (Fintrol-5) is distributed by handor powered-seed spreaders or dribbled into the propeller wash in waters of appropriate depth. The Fintrol-15 formulation, which is designed to treat much deeper water, should be dispensed from a spreader in order to obtain more uniform distribution of the toxicant.
Gaseous toxicants (chlorine and anhydrous ammonia) usually are introduced underwater through a hose. If large tanks of gas are used, they are hauled to the pond edge and the gas introduced at various points around the shoreline depending upon the size and shape of the pond. However, if the cylinders or tanks are small enough, they can be carried around the pond in a boat. In any case, a high degree of caution should be exercised to avoid accidental release of gas with the possibility of extremely serious consequences. Application of chlorine in hatchery ponds sometimes has been accomplished with relative ease by injecting the gas into the water supply line used to fill the ponds.
The application of organophosphates almost always is accomplished by pouring solutions of these toxicants into the propeller wash of an outboard motor. The more toxic materials, especially, are never sprayed, because of danger to the applicator.
Sodium cyanide is another toxicant that can be safe or extremely hazardous, depending on the caution and judgement exercised by the user. The material usually is dispersed in large ponds by towing sacks of cyanide eggs or briquettes behind a boat until they dissolve. Two men can treat small ponds by towing a sack or wire basket suspended from a rope long enough to reach across the pond. Application of sodium cyanide in solution almost always is to be preferred over the simple expedient of tossing briquettes into the water to dissolve.
One point that hardly can be emphasized too strongly is that the best toxicant available will fail if target organisms are not exposed to an adequate concentration for a long enough period of time to absorb a lethal dose. Thus, careful planning, preparation, and application are indispensible to effective control of pest organisms.
Many kinds of fishes (both indigenous and exotic) are cultured in various parts of the world. Hora and Pillay (1962) list 69 species cultured in the Indo-Pacific region alone. Bardach (1968) lists a number of fishes that are of primary importance in fish cultural activities in several countries, and also discusses the methods and problems of producing various species of fishes and invertebrate food organisms. One of the more efficient methods for achieving maximum production of food fish in ponds is that of mixed stocking in which as many as five or six species that occupy different ecological niches are included so as to make maximum use of the available food supply.
In the United States, some 20 species of fishes have been raised commercially for bait (U.S. Bureau of Sport Fisheries and Wildlife, 1970b). More than that number of species of sport and food fishes (both warm-water and cold-water) have been produced commercially for market or for stocking privately owned waters, and we have been advised that at least 75 varieties of aquarium fishes are cultured in ponds in southern Florida. During the period from about 1878 to 1943 a considerable amount of effort was devoted to propagation of marine fishes in publicly owned hatcheries, but the program was terminated in 1952 and then resumed on a limited scale in 1965.
Fish hatcheries and fish production ponds in the United States fall into two general classes: those owned and operated by governmental agencies, and those in private ownership. Most publicly owned facilities are devoted to production of sport fishes for stocking ponds, lakes, and rivers for the benefit of huge numbers of anglers, but a few are used primarily for research on problems of fish culture and fishery management. The importance of sport fishing, both from the recreational and the economic point of view, is demonstrated by the fact that 24,076,148 fishing licenses were purchased in 1969 at a cost of 87,500,774 US dollars. Privately owned facilities are used for a variety of commercial purposes including the following: production of food, sport, bait, and aquarium fishes; production of shrimp, crayfish, and shellfish; and fee fishing (pay lakes).
Fish hatcheries owned by governmental agencies usually are operated by a resident manager and a staff of assistants. Production ponds vary in size from less than 0.2 to more than 12.0 ha (0.5 to 30.0 a), but the optimum size at Federal hatcheries is regarded as about 0.3 ha (0.75 a). The combined surface areas of ponds at various federally owned fish hatcheries range from less than 8.1 to more than 40.5 ha (20 to 100 a).
Privately owned hatcheries and fish production facilities in the United States vary tremendously in size. Some are essentially one-family operations, while others are owned by large corporations and operated by sizeable staffs. Ponds for producing aquarium fishes usually vary in size from less than 9.3 m² (100 sq ft) to about 185.9 m² (2,000 sq ft), with an average area of about 148.7 m² (1,600 sq ft) and a depth of 2.1 to 3.0 m (7 to 10 ft). Individual producers may operate from three to more than 300 ponds, but the average is reported to be from 100 to 125 ponds.
The ponds used for rearing game, bait, or food fishes range in size from less than 0.1 to about 20.2 ha (0.25 to 50.0 a), although a few irrigation ponds used incidentally for rearing buffalo in the State of Arkansas are larger than 121.4 ha (300 a). The average size of catfish farms (water impoundments) in the Deep South is about 15.4 ha (38 a), but the majority of farms range from 4.0 to 12.1 ha (10 to 30 a) (Jones et al., 1970).
Licensed commercial fish farming has been conducted on a rather limited scale in Canada for many years. In the Province of British Columbia, for example, some 30 fish farms were reported in 1970, having a combined acreage of less than 40.5 ha (100 a). The Province of Saskatchewan likewise reported fewer than 10 such ponds in 1969. In that year, however, an experiment was conducted in Manitoba which stimulated strong interest in rainbow trout production in lakes that freeze out regularly. As a result, Saskatchewan alone issued 160 licenses for experimental fishing purposes during the spring of 1970, and there is every indication that further expansions in this type of fish farming are forthcoming.
Mainland China, with its vast land mass, its millenia of fish cultural experience, and its intensive husbandry methods produces more fresh-water fish than any other nation. In 1959 the area under fish cultivation was said to be about 2,569,781 ha (6,349,928 a), and in 1965 China reported production of 1.5 million tons of the estimated world production of 3 million metric tons of fish cultured in fresh and brackish waters (Bardach, 1968). Hora and Pillay (1962) tabulated the estimated area of cultivable inland waters of 19 countries in the Indo-Pacific Region, but showed that only a small fraction of the available water was utilized for fish cultural purposes. Professor Homer S. Swingle of Auburn University, Auburn, Alabama, provided the following estimates to us on the area of fresh and brackish water ponds in various regions throughout the world: Asia -- 2,072,250 ha (5,120,530 a); Europe -- 686,340 ha (1,695,945 a); Africa -- 27,236 ha (67,300 a); Near East -- 5,973 ha (14,760 a); North America (excluding Mexico) -- 607,042 ha (1,500,000 a); Spanish Americas and Brazil -- 47,207 ha (116,649 a); world total -- 3,446,048 ha (8,515,184 a).
In the United States, state agencies have far greater responsibilities for fish management than do Federal agencies, hence in 1965 state expenditures for fish production and distribution amounted to about 73 percent of the total public outlay for these purposes (Stroud and Martin, 1968). In 1965 there were 410 state fish hatcheries and rearing stations (U.S. Bureau of Sport Fisheries and Wildlife, 1968), and by 1967 the number had grown to 473 (U.S. Bureau of Sport Fisheries and Wildlife, 1967). Of this number, 161 produced warm-water fishes, 283 produced cold-water fishes, and 29 produced both. All but two states, Delaware and Mississippi, operated facilities for producing fish in 1967.
In 1970 there were 92 Federal fish hatcheries located in 41 states, including 34 hatcheries for warm-water fishes, 45 for cold-water fishes, and 13 producing both. Only Alaska, Connecticut, Delaware, Hawaii, Illinois, Indiana, Maryland, New Jersey, and Rhode Island lacked Federal hatcheries (U.S. Bureau of Sport Fisheries and Wildlife, 1970a). About 73 percent of Federal expenditures at fish hatcheries was devoted to production of trout and salmon in 1966, and accounted for approximately 60 percent of the total national production of cold-water fishes.
Information on the numbers of privately owned hatcheries is less complete, but data from 46 states have been summarized as follows by Stroud and Martin (1968). In 1966 there were 551 trout hatcheries (rainbow, brown, and brook trout) in 31 states, 505 warm-water hatcheries (chiefly largemouth bass, bluegill, and channel catfish) in 24 states, and 778 minnow hatcheries (fathead minnow, golden shiner, goldfish, and suckers) in 22 states. States containing the greatest number of these types of hatcheries were Wisconsin (trout), Arkansas (warm-water), and Missouri (minnows).
Figures on the total number of acres of hatchery ponds used for commercial production of sport fish species in the United States and the value of the fishes produced annually are not available, but in 1966 about 12,145 ha (30,000 a) of ponds devoted to bait fish production produced a crop having a market value of some $30 million (Maloy, 1967). In 1969 about 1,300 persons and firms were engaged in farm catfish culture in the United States, with more than 16,188 ha (40,000 a) in production (Jones et al., 1970). The retail value of the catfish crop in 1969 was estimated at about $75 million (U.S. Bureau of Sport Fisheries and Wildlife, 1970b). Probably 90 percent of the pond-reared aquarium fishes produced in the United States come from about 150 hatcheries located in southern Florida. The wholesale value of the Florida crop in 1969 amounted to about $30 million.
Bardach (1968) states that “All aquaculture is done for profit, even in the planned Soviet economy, and the profits are, at times, substantial (algae culture in Japan, oyster culture in Brittany, and trout and catfish culture in the USA)”. There are distinct differences, however, in management practices followed in the operation of publicly and privately owned fish production facilities, and the differences may be largely attributable to one critical factor: operations in private ownership must show a profit -- or die.
In North America most farm and ranch ponds are relatively small artificial impoundments that have been constructed on privately owned property. Definitions to distinguish between ponds and lakes appear to be wholly arbitrary, and some bodies of water more than 80.9 ha (200.0 a) in area are called ponds. However, most farm and ranch ponds range in size from about 0.10 to 2.02 ha (0.25 to 5.0 a). Size usually depends upon the amount of money and land available for construction, suitability of the topography, availability of water, and the intended purpose of the pond. There has been gradual increase in average size of farm ponds built during recent years resulting largely from two factors: financial aid for pond construction has become available through agricultural assistance programs, and experience has shown that large ponds generally provide better fishing success over a period of years than do small ponds. There are farm and ranch ponds in all states in the United States, but the south central, southeastern, southwestern, and midwestern states contain the largest numbers of ponds in the order listed (Arakie, 1968).
Farm and ranch ponds have been constructed to serve a wide variety of purposes. Most of the early farm ponds were constructed to provide water for livestock. Nearly a century ago (in 1872) the first funds were appropriated by the United States Government to make free distribution of fish for stocking purposes (compton, 1952). Interest in managing farm ponds for fishing became evident about the turn of the century and increased during World War I (Meehean, 1952). Edminster (1947) points out many of the following benefits derived from ponds: soil and water conservation; a source of water for household use, irrigation, agricultural and horticultural sprays, and fire protection; enhancement of wildlife values; recreational uses including fishing, swimming, picnicing, boating, skating, hunting, and trapping; production of bait fish for private use or to provide additional income, and production of fish for table use. King (1960) conducted a survey of 1,000 ponds stocked from Federal hatcheries in the United States, and reported the purposes served by the ponds as follows: livestock water, 80 percent; fishing, 70 percent; irrigation water, 13 percent; swimming, 9 percent; wildlife, 5 percent; other purposes, 4 percent.
In the 1930's, the initiation of several soil and water conservation and land-use programs greatly accelerated the rate of pond building in the United States. Compton (1952) reported that from 1936 to the end of 1950, the Production and Marketing Administration made payments for the construction of 823, 797 ponds for livestock water, and that the Fish and Wildlife Service estimated that there were about 1,576,000 farm and ranch ponds of all sizes in the summer of 1950. By 1960 there were about 1,431,000 farm and ranch ponds less than 4.1 ha (10 a) in area, and their average size was slightly more than 0.4 ha (1 a) (King et al., 1961). Of this number, only 8,000 were managed for cold-water species. In 1960 the Department of Agriculture estimated that 912,000 permanent ponds having a combined area of 340,348 ha (841,000 a) had been constructed under agricultural assistance programs (Arakie, 1968). By 1965 there were about 890,328 ha (2.2 million a) of farm ponds, and it is estimated that by the year 2000 there will be a total of 1,497,369 ha (3.7 million a) of farm ponds (U.S. Bureau of Sport Fisheries and Wildlife, 1968).
Several American and Canadian agencies disseminate information about construction, development, stocking, and management of ponds, and some employ fishery biologists or technicians who give personal assistance to pond owners. The services rendered vary widely, but pond owners now are able to count on expert help with most of the management problems that arise.
Under provisions of the Prairie Farm Assistance Act, the Canadian Government assisted land owners in the Province of Saskatchewan in building about 3,800 stock-watering dams during the period from 1937 to 1952 (Rawson and Ruttan, 1952). A questionnaire survey conducted by these authors in January, 1952, revealed that there were not more than about 100 ponds in any of the other provinces, and that five of them reported no farm fish ponds. Since then there has been an increased interest in farm ponds for fishing, and by 1959 there were no less than 10,500 usable farm ponds in southern Ontario alone (McCrimmon, 1961). In 1970 there were about 150 fish ponds in the Province of British Columbia, with another 300 to 350 ponds in the Atlantic maritime provinces. The sport species of most interest and most amenable to pond culture are rainbow and brook trout, although centrarchids frequently are stocked in ponds which become too warm for trout in summer (Smith, 1961). According to McCrimmon (1961), a surface area of 0.1 to 0.8 ha (0.25 to 2.0 a) is preferred for trout ponds.
The basic causes of fishery management problems in ponds in the United States stem from the fact that pond owners are poorly informed or lack interest. Ponds that are well planned, well constructed, and properly stocked often produce satisfactory fishing for considerable periods of time with only a modicum of care on the part of well informed and properly motivated owners or managers. However, even intelligent management and diligent care can be negated by a variety of circumstances including accidental or unauthorized introduction of undesirable species, fish kills resulting from various causes, illicit fishing, and unfavorable weather conditions with the result that intensive management efforts are required to bring the population back into a balanced, productive condition.
Moss and Hester (1956) studied the fish populations in 106 farm ponds in the State of Alabama, and concluded that two of the major factors responsible for poor fishing success were the presence of wild fish in the ponds before hatchery fish were stocked and the migration of wild species into ponds from which they had been eliminated prior to stocking.
Kelly (1961) reported the results of a study made in Alabama which illustrates the need for chemical renovation of substantial numbers of ponds to prepare them for stocking. wild fish, which were potential causes of failure, were present in 213 (25.2 percent) of the 845 ponds checked.
King (1960) surveyed 1,000 fishing ponds that had been stocked with fish from national fish hatcheries to determine how much recreational fishing was afforded. Fishing was poor in 119 of the ponds for a variety of reasons including the following: too many small bluegill (16 percent); presence of wild fish (12 percent); overstocked originally (5 percent); and too many bullhead (4 percent). Thus, the use of toxicants as one of the remedial steps in improving fishing success was indicated in 37 percent of the problem ponds. The application of toxicants should not be regarded as a cure-all, however, because there quite frequently are basic deficiences in pond construction or management practices that must be corrected before substantial benefits can be realized from any effort to improve the fish population. These include: extensive areas of shallow water; turbidity resulting from unvegetated pond banks, bare areas in the watershed, or lack of fencing to exclude livestock; improper fertilization; undesirable growths of aquatic plants; and selective fishing for predatory species.
Two of the oldest methods of controlling pondfish populations are the application of fish poisons and the draining and drying of ponds. On many occasions these methods of managing farm and ranch ponds still may be essential, but there are several reasons for the increasing tendency to regard them as the last resort. The need for complete eradication of pondfish populations has been reduced significantly by development of techniques whereby partial or selective control can be achieved through the use of chemical toxicants and remedial stocking of predatory species. Application of these methods often extends the period of satisfactory fishing for years, and some agencies now provide pond owners with detailed instructions on partial poisoning of forage fish populations. Furthermore, the costs of partial treatments are much lower than those of complete treatments, and it may not be necessary to curtail fishing.
Some of the more important shortcomings of the drain-and-dry technique are the risk of unwanted fish surviving if drainage is incomplete, the loss of valuable water, and the delay in restocking caused by lack of enough water or unavailability of hatchery fish at certain times of the year. Even under ideal conditions fishing seldom can be resumed for at least 18 months after a pond is drained, and many pond owners are not inclined to accept such loss of fishing opportunity.
Remedial stocking with considerable numbers of fingerling and intermediate largemouth bass to control excessive numbers of bluegill has been tried, but found to be less effective than selective poisoning in establishing a desirable bass-bluegill ratio (Clark, 1954). Rounsefell and Everhart (1953) urged that the stocking of northern pike and walleye to control populations of warm-water fishes be approached with extreme caution in view of the lack of proven value of the method. Snow, Ensign and Klingbiel (1960) stated in regard to bluegill that stocking of predators has been tried often as a population control measure, but that anglers catch the predators too quickly to produce beneficial results.
The effects on fish populations of artificial drawdown of water levels in impoundments of different sizes are discussed by Bennett (1962), Wood and Pfitzer (1960), Heman, Campbell, and Redmond (1969), and Pierce, Frey, and Yawn (1965). The results of water level manipulation have been favorable or unfavorable depending upon a variety of circumstances. Although the method holds real promise as a management tool under some conditions, a considerable amount of work remains to be done before its worth can be fully assessed.
Several other methods of manipulating pondfish populations have been tried with varying success. Mechanical removal of fish by seines, nets, traps, and electrical shockers has proven in many cases to be inefficient, laborious, or expensive as a practical means of fish management. Control of forage fish populations by physical destruction of nests has been attempted, but has not been recommended except for small ponds having rather limited spawning areas that are easy to observe.
In view of the difficulties involved in effecting population control by the methods discussed above, it is evident that the use of chemical toxicants presently offers the most efficacious, economical, and widely applicable means of manipulating fish populations. Snow, Ensign and Klingbiel (1960) made the unequivocal statement that fish toxicants are the most economical means to achieve population control of bluegill. Without doubt this statement can be applied to several other species as well, especially with the advent of toxicants that show greater selectivity.
The need for control of pondfish populations is recognized so widely that most states having large numbers of farm ponds publish detailed instructions on the use of rotenone and other toxicants as an aid to pond owners. Methods of calculating the volume of water to be treated are given, techniques and timing of toxicant application are recommended, and the choice of toxicant concentrations to be used is explained on the basis of fish species to be controlled. Some of the methods, precautions to be observed, and frequent causes of failure are discussed by Clemens and Martin (1953), Bennett (1962), Meyer (1966) and numerous other authors.
The commonest problem in farm and ranch ponds, the overpopulation of bluegill or other forage species, often can be remedied by selective control with rotenone or antimycin. The methods and some results of applying these toxicants are discussed by Swingle, Prather, and Lawrence (1953), Bennett (1962), Thomaston (1965), Callaham and Huish (1968), Stinauer (1968) and Burress and Luhning (1969b). If rotenone is used, the treatment must be made at the right time of day under carefully prescribed weather conditions, and even then several treatments may be required to obtain a kill of the desired magnitude. If the proper concentration of antimycin is used, one treatment, or two at most, will be sufficient. The concentration of antimycin must be selected with regard to water temperature and pH, but weather conditions are not of critical importance. If marked diurnal elevations of pH occur, it is best to apply antimycin early in the morning. As Thomaston (1965) pointed out, the number of forage fish remaining after thinning is of greater importance than the number removed. The degree of removal can be determined best by evaluations based on standardized seine hauls made before and after treatment.
Population problems that result from the invasion of warm-water farm ponds by gizzard shad, cyprinids and centrarchids (except crappie spp. and warmouth) often can be corrected or alleviated by the selective thinning technique. However, if carp, buffalo spp. or crappie are too numerous, the best solution may be to eliminate the populations with rotenone or antimycin. If bullheads are the problem, selective control by means of copper sulfate applications may be possible (Toole, 1968), or complete removal may be accomplished with rotenone. Some biologists feel that it is preferable to make two closely spaced treatments with rotenone to kill resistant species rather than to use a single treatment of double strength.
Trout ponds that are invaded by warm-water species sometimes can be restored by careful application of antimycin or rotenone to the epilimnion.
Both rotenone and antimycin can be detoxified with potassium permanganate (Lawrence, 1956 and Gilderhus, Berger, and Lennon, 1969). Chlorine, chlorinated lime, and chlorine dioxide also have been used to detoxify rotenone, but they are felt by some to be costly and difficult to apply (Meyer, 1966). On the other hand, Jackson (1957) found that chlorine in the form of chlorinated lime was more convenient to use than potassium permanganate. Loeb and Engstrom-Heg (1970) reported that potassium permanganate and chlorine can be neutralized instantly with tannic acid or sodium thiosulfate if this degree of control is needed. Farm ponds that do not overflow rarely need to be detoxified, and the need for detoxification in those that do overflow can be eliminated if water levels can be lowered sufficiently prior to treatment.
Clemens and Martin (1953) made experimental applications of emulsifiable and powdered rotenone in 30 ponds in Oklahoma, and used the following criteria for evaluating the completeness of the kill: 1) minnows could not live in samples of water taken at various levels from top to bottom; 2) no indication of live fish, especially along the shore, could be detected; 3) recently killed fish were not found on the days subsequent to the application; 4) seining and netting operations revealed no fish; and 5) no fish could be obtained by further application of rotenone. When 18 of the ponds were checked 2 to 3 months after treatment to validate the previous evaluation of the kill, fingerling fish were found in 28 of the 30 ponds. Thus, the investigators concluded that there can be no certainty of a complete kill unless a pond is drained.
Kirkwood (1957) treated 60 small ponds in Kentucky with 1- to 2-mg/l (ppm) concentrations of powdered and/or emulsifiable rotenone applied by eight different methods. Of 43 ponds that were later examined by seining or spot-poisoning with rotenone, 62 percent were found to be free of fish, and the powdered rotenone was deemed to be slightly less effective than the emulsifiable formulations.
Turner (1959) tested a 1-mg/l (ppm) concentration of four different products containing rotenone in 56 farm ponds in Kentucky, and evaluated completeness of kill from 1 to 6 months later by observation, extensive seining, spot-poisoning with rotenone, or complete re-treatment with a 2-mg/l (ppm) concentration of rotenone. He reported a complete fish kill in 97 percent of 24 ponds treated during the summer, whereas a complete kill occurred in only 72 percent of the 32 ponds treated in the fall. The greater success of summer treatments was attributed to stagnation of the deeper water, which prevented fish from retreating to lower strata to escape the toxicant.
The results of a toxicant application that to all indications produced a total kill sometimes are judged by whether or not the undesirable species re-enter the creel in following years. If they do not, the effectiveness of treatment is evident, but, if they do, it seldom is possible to prove beyond question that the kill was incomplete or that the unwanted species could not possibly have re-invaded the treated water or been re-introduced. When survival of target species can be proven, the question that remains is whether the toxicant somehow was deficient or whether the application was inadequate, or both.
The effectiveness of selective thinning treatments for improving fishing success in ponds depends upon a host of factors in addition to the qualities of the toxicant used. During the period from 1955 to 1962 about 100 ponds in Georgia were partially poisoned to eliminate a portion of the intermediate-size bream (centrarchid). All attempts to correct an unbalanced population including species other than largemouth bass and bream were unsuccessful (Thomaston, 1965). Final evaluations of the success of treatments in some ponds were not possible for as long as 3 years afterward, but population balance was achieved in five of eight ponds having a variety of problems regarded as typical. Jenkins (1956) removed from 80 to 95 percent of the entire fish populations from four lakes in Oklahoma, and concluded that such treatment in lakes where carp and gizzard shad are not present, or are eliminated, followed immediately by stocking with fingerling bass at the rate of about 371/ha (150/a), can improve fishing for game and panfishes within 2 years. He cautioned, however, that this procedure is risky if carp and shad are present.
The list of factors which contribute to failure of pond renovations is long. Among the physical factors are the following: incomplete coverage or inadequate dispersion of toxicants in shallow and deep water, in marshy pond borders, in dense beds of submersed aquatic weeds, in burrows made by a variety of aquatic animals, in springs, seeps or inflowing streams; water temperatures that are too high or too low; presence of a strong thermocline; high turbidity (either organic or mineral); soft, mucky bottoms that permit fish to burrow in to escape the toxicant; dilution of toxicants by untimely rains; and failure to treat isolated potholes in dewatered ponds. The most important chemical factors are elevated pH levels and excessively high alkalinities.
Biological factors include: resistance of some species or individuals even to strong doses of toxicants; hatching of eggs after the period of toxicity has passed; re-invasion of fish through pond overflows; re-introduction of fish from other bodies of water higher up in the watershed; and use of a toxicant that is repellent.
Clemens and Martin (1953) found a total of 18 species of fish remaining in 16 ponds that had been treated with rotenone. There were green sunfish in 11 ponds, black bullhead in four, bluegill and mosquitofish in three ponds each, red shiner in two, and four other species in one pond each. Jenkins (1956) stated that the order of apparent increasing tolerance to rotenone of several species was as follows: gizzard shad, carp, largemouth bass, redear sunfish, black crappie, bluegill, white crappie, green sunfish, warmouth, and black bullhead. Gilderhus, Berger, and Lennon (1969) tested antimycin in 20 ponds and lakes and five streams, and showed that catfishes of several species, bowfin, gars, and goldfish are among the most resistant species; of the centrarchids, largemouth bass, smallmouth bass, crappie, warmouth, and pumpkinseed are the more tolerant; the other centrarchids, carp, and buffalo were moderately sensitive; and trout, yellow perch, gizzard shad, white sucker, and certain minnows are quite sensitive.
The behavior of some fishes when exposed to irritating or repellent toxicants has a large bearing on their ability to survive. As mentioned above, bullheads are known to escape by burrowing into soft pond bottoms. Mosquitofish and small green sunfish frequently survive even high concentrations of toxicant by seeking shelter in very shallow, weedy areas along pond margins where dispersion of the toxicant is poor. Bluegill especially show a strong tendency to seek refuge in dense growths of aquatic weeds and to remain there until the period of toxicity has passed. One of the marked advantages of antimycin is that it does not repel fish, and most are likely to have incurred a lethal dose before they begin to seek fresh water.
Other human factors than those implied above which contribute to failure of reclamation efforts include underestimating the volume of water to be treated, using the wrong formulation of toxicant, treating at the wrong time of the year (largely in selective thinning efforts), failure to remove a large enough segment of the population by partial poisoning, and failure to add a sufficient number of the predatory species used for remedial stocking. Thus, human error appears to be one of the most serious causes of failure and one of the shortcomings most susceptible to correction. The knowledge that a reclamation may present difficulties often evokes the automatic response of multiplying the concentration of toxicant to be used. The usual justification for such overdosing is that it provides the easiest way to do the job quickly, yet with a reasonable expectation of success. Thus, it is assumed that the addition of excess toxicant will make up for lack of planning and preparation, inadequacies in application equipment or methods, hasty treatment, and any other deficiencies on the part of the applicator.
There are certain procedures that should be used to increase greatly the possibility of obtaining a complete kill of fish. If the situation permits, ponds that have weedy or marshy edges should be drawn down enough to deprive fish of this kind of cover. Otherwise, pond edges should be treated first to drive fish away from the weeds. Beds of submersed plants that are contributing to the problem should be controlled by drawdown or by herbicides. Special care should be taken to assure good distribution of the fish toxicant and herbicide throughout the stands. If areas of deep water cannot be reduced by dewatering, toxicants in solution can be spread in these strata by pumping through a hose that terminates in a capped section of 12.7-mm (0.5-in) pipe having holes drilled on all sides, or by dragging a weighted hose having a funnel inserted in the end. Powdered rotenone in weighted, towable sacks also can be used, or Fintrol-15 can be applied to eliminate scale=fishes if the water does not exceed a depth of 4.6 m (15.0 ft). Operation of an outboard motor over most of the pond area helps to distribute toxicants applied on the surface to a depth of about 1.8 m (6.0 ft). Water in deeper areas of the pond can be mixed to a degree by running the motor of an anchored boat up to full throttle for 15 minutes or more, providing that the water is not muddied.
When a choice of treatment time is possible, it generally is desirable to treat as close to the time of restocking as possible. It also is preferable to treat at times other than the nesting seasons to avoid the possibility of eggs surviving to cause re-infestation.