A questionnaire concerning the use of toxicants to remove undesirable fish was sent to 1,300 different locations in the world. One-hundred-fifty-nine replies were received from 39 states and two territories in the United States, seven provinces in Canada, and 28 countries in South America, Africa, Europe, and Asia. Among these replies, 113 included data on chemical removal programs. The other respondents usually informed us that no attempts at reclamation had yet been made by them, but they expressed interest in seeing the results of the review.
The response from state and territorial fishery agencies in the United States was good. Thirty-nine states and both territories replied to the questionnaire, submitting data in 65 of 81 replies in the form of letters, articles, and charts. The territories of Puerto Rico and Guam and the State of Hawaii were the only respondents that never have used toxicants as part of their management programs. The other 49 states have reclaimed waters by chemical methods mainly since 1953. The vast majority of the lakes treated totally provided improved fishing. Partial treatment, principally used since 1956 on lakes, has not been as successful, but the costs have been less. Stream reclamation has been practiced mainly in the last 9 to 10 years, but it has not become a major tool of fishery management. The principal toxicant used in the United States is rotenone.
Six of the 11 northeastern states contributed information. Fish management in this area centers on trout fisheries in ponds and streams, necessitating control of chain pickerel, sunfishes, and yellow perch. Vermont was the first to use a toxicant against unwanted fish when copper sulfate was applied to a lake in 1913. Since 1946, Vermont has reclaimed 27 ponds with rotenone. New Hampshire treated most of its problem ponds and streams between 1938 and 1956, and now practices re-treatments as necessary to maintain good sport fisheries. Massachusetts has subjected 250 ponds, totalling 6,070 ha (15,000 a), to partial or complete reclamation. About one-half of the ponds were restocked with trout and the others with warm-water fishes. Maine and New York also have been active in reclaiming ponds. More recently, Maine, Massachusetts, and West Virginia have reclaimed both cold-water and warm-water streams. All respondents implied that chemical removal of undesirable fishes is the most effective management practice to provide better fishing.
The northeastern states have used mostly rotenone in reclamations, but Maine, New Hampshire, and New York recently found that antimycin is quick and easy to apply, and produces desired results sooner than rotenone. Copper sulfate, Dibrom-malathion, Thiodan, and toxaphene have been tried, but discontinued because of toxicity to aquatic life in general, persistence in the environment, or other reasons.
Most of the southern states responded to the questionnaire. Gizzard shad cause many problems in the South, and low concentrations of rotenone are highly selective against this species. Farm Ponds abound in this area, hence much has been published on managing this type of water. Both cold- and warm-water species are cultivated, with emphasis on the centrarchids and a new interest in channel catfish.
Alabama and Georgia have extensive programs in reclaiming farm ponds for largemouth bass-bluegill production. Alabama routinely requires that all privately owned ponds and lakes be renovated before they are stocked. In Georgia, where over 3,000 farm ponds are reclaimed each year, one-half of the fresh-water fishing is done in farm ponds. Antimycin has been tested successfully in Georgia ponds for selective thinning of bluegill.
Florida has many acres in lakes which are treated with rotenone for selective removal of gizzard shad. In a large-scale application, four lakes totalling 17,402 ha (43,000 a) were treated during 1957 to 1959. Re-treatments have been necessary. Other states have treated reservoir areas before and after impoundment. Public fishing lakes also are treated by the states.
Attempts to manage warm-water streams have been made by Arkansas and Florida before 1965 and later by Tennessee. Management of cold-water streams has been tried on a limited scale in Georgia, Kentucky, North Carolina, and Tennessee.
Other toxicants which have been used besides rotenone and antimycin include chlorine in Maryland, endrin in Tennessee, copper sulfate in Virginia, and sodium cyanide in Kentucky. The major toxicant has been rotenone, partly because of its selectivity to gizzard shad, a major undesirable fish.
Of the 11 Midwestern states, nine reported extensive use of toxicants to control fish principally in warm-water lakes, reservoirs, and streams. Rotenone was most often used. Toxaphene, the second most used chemical in the United States, was applied prior to 1965 by Iowa, Minnesota, North Dakota, South Dakota, and Wisconsin. Thereafter, it was employed only by South Dakota and Wisconsin. Earlier, two other Midwestern states tried toxaphene and stopped using it: Michigan from 1947 to 1954 and Nebraska in the mid-1950's. It was too toxic to birds and mammals, and too persistent in the environment. Within the past 4 years several states have reported increased usage of antimycin in all types of water. In fact, Iowa stated that antimycin is the new hope for solving fish management problems. Sodium cyanide also has been used in Missouri, South Dakota, Nebraska and Indiana, but only Nebraska and Indiana continue to use it at present. Both copper sulfate and Bayluscide have been employed to a limited extent in Ohio.
Major problem fishes include centrarchids and carp in Missouri; sunfishes in warm waters in Minnesota; bullheads, crappies, and carp in Iowa; suckers and dace in South Dakota; bullheads, green sunfish, carp, and goldfish in Ohio; carp and freshwater drum in Nebraska; green sunfish, bullheads, crappies, and carp in ponds, and carp, shad, buffalo and bullheads in lakes in Illinois; stunted centrarchids, carp, suckers, and bullheads in Wisconsin; and centrarchids, especially bluegill, suckers, and yellow perch in Michigan.
The Midwestern states most active in warm-water lake reclamations include Iowa, Michigan, Minnesota, North Dakota, and Wisconsin; the cold-water lake reclamations include Michigan, Minnesota, and South Dakota. The states with major reservoir treatment programs include South Dakota, Ohio, and Nebraska. States with many farm ponds to manage include Missouri, South Dakota, Nebraska, Iowa and Illinois.
The states concerned with cold-water stream reclamations include Michigan, Nebraska, South Dakota, and Wisconsin. However, none has treated many miles of streams. Warm-water stream reclamations have occurred in South Dakota, Nebraska, Michigan, Missouri, Wisconsin, and Indiana. These constitute about one-half of the total miles of warm-water streams reclaimed in the United States.
Some of the states have compiled summaries which illustrate the scope of the reclamation work done in the Midwest. From 1941 to 1968 Wisconsin treated 255 lakes and 21 streams using rotenone, toxaphene, Aqualin, and antimycin. Michigan, which treated waters mainly for trout management from 1934 to 1967, reclaimed over 450 lakes and streams. From 1934 to 1942 only rotenone was used on 32 lakes. Nothing was done from 1943 to 1945 during World War II. Forty-five lakes and ponds were renovated from 1947 to 1954. Most of the reclamations occurred thereafter, and included 243 lakes and streams from 1955 to 1963.
Fifteen of the 16 Western states responded to the questionnaire. These states were responsible for a voluminous amount of material in the form of published and unpublished articles and informative letters. Most of the material consisted of Federal Aid in Fish Restoration Act reports, which until recently were available only from the state agencies. The reports are now available from the Denver Public Library, Library Conservation Center, Denver, Colorado.
The major problem fishes in cold waters in the West are carp, goldfish, suckers, bullheads, sticklebacks, yellow perch, channel catfish, and squawfishes. In warm waters, the problem species are gizzard shad, white sucker, cyprinids, black bullhead, and yellow perch.
There were several early users of toxicants in the Western states. Selective use of rotenone against Utah chub was introduced by Utah in 1938. California followed by treating lakes for carp in 1941. Oregon also got an early start and had treated most of its cold-water lakes prior to 1953. In general, the states have practiced chemical reclamation extensively since 1943, with only Hawaii abstaining. Washington stated that it had reclaimed waters with toxicants 5 to 8 years ago. The state now is doing little along this line, because most waters were reclaimed earlier, and now are done on a maintenance basis.
The Western states mainly have used rotenone in their reclamation attempts, but have tried other toxicants. Toxaphene has been the most widely tried of the other toxicants, but it never gained acceptance in this part of the country. Alaska, Utah, California, Colorado, Oregon, Montana, and Idaho tried toxaphene, but found it too toxic. Alaska stopped after 1963, Montana in the early 1960's, and Idaho after 1967. Squoxin, a new selective toxicant for squawfishes, has been tried experimentally in Idaho.
California and Texas manage their lakes mainly for warm-water species, but Idaho, Montana, Oregon, and Washington focused most attention on cold-water species in the past. No Western state, except New Mexico, has reclaimed warm-water streams to any extent, but treatment of cold-water streams has been extensive in California, Idaho, Montana, Oregon, Utah, and Wyoming.
Several states submitted good summaries and data on their reclamation work. Alaska has reclaimed 46 lakes with rotenone, and 10 with toxaphene. They were restocked with trout, salmon, or Arctic grayling. California reports that in the period from 1948 to 1968, 260 lakes and reservoirs and 75 streams were treated. Most were treated with rotenone, one with toxaphene, and several with antimycin. Recently, Oregon successfully applied antimycin in a reservoir and rotenone in the head-water river. Rotenone was the principal toxicant used in Idaho until antimycin was found to be much more effective against carp and suckers. In its 25 years of reclamation work, Idaho treated 102 lakes and reservoirs and 23 streams. Montana submitted data on three of their most important projects, which happened to be streams. Attempts were made to eliminate goldeye and carp in Marias River, and suckers, carp, and yellow perch in Canyon Ferry Reservoir. The Montana biologists questioned the value of pre-impoundment fish eradication projects, because fishing seemed to be just as good in non-treated waters. New Mexico has carried on a rather extensive program of stream reclamation to remove a variety of undesirable fishes. Usually these projects were a part of a larger watershed program which included reservoirs.
State game and fish commissions have been quite active over the past 30 years, and seem to be headed for larger programs in the future. The emphasis is toward more selective compounds such as antimycin and Squoxin, and away from persistent and highly toxic compounds such as toxaphene. In the late 1950's Les Veaux (1959) determined from his questionnaire sent to state agencies that aquatic biologists desired the development of selective toxicants to control certain problem fishes in each area of the country. More stream reclamations are expected as better toxicants became available.
The Federal Government of the United States, especially the Division of Fishery Services, U.S. Bureau of Sport Fisheries and Wildlife, has been involved in fishery management on federally owned lands. Federal personnel who responded to our questionnaire supplied bibliographies and information on field experiences which were not obtainable elsewhere. For example, Mr. Braden Pillow, a biologist with the Division of Fishery Services, Portland, Oregon, stated that of the more than 75 reclamations in which he participated, only two could be classed as unsuccessful. Re-treatment was required in 5 to 15 years due to re-infestation caused by overflow, re-introductions by humans, and other reasons. Complete kills were rare, especially in large waters or entire watersheds, with such resistant species present as carp, goldfish, or bullheads. He believes that the over-all effects of well executed attempts at chemical control are beneficial and productive of good fishing, and adds that partial treatment or selective reduction of undesirable fish has a great potential for future use in fisheries management.
Representatives of the Division of Fishery Services, Atlanta, Georgia sent inspection reports that describe their chemical treatments of lakes at five military bases. The lakes were treated with antimycin to remove stunted bluegill and other undesirable species so that channel catfish or largemouth bass could flourish.
The Library Reference Service, Denver Public Library, which has a contract with the U.S. Bureau of Sport Fisheries and Wildlife, sent five sections of a bibliography concerning unpublished reports of projects financed under provisions of the Federal Aid in Fish Restoration Act. The Library Reference Service also furnished copies of reclamation reports which were unavailable elsewhere. This material was extremely valuable because it contained much information on stream reclamations that previously was unknown to us.
Replies from other sources were received. The Tennessee Valley Authority (TVA) indicated that fish management programs in TVA lakes are the responsibility of the state game and fish commissions. The only use of toxicants by TVA is for fish sampling purposes. Industry's only reply came from S.B. Penick & Company, a major supplier of rotenone. They sent a bibliography on the toxicity and chemistry of rotenone.
Seven of the 11 provinces of Canada responded to the questionnaire, sending 19 replies of which 10 supplied data on chemical removal of fishes. In general, the Canadian activities have been rather limited, with only 1 percent of fishery expenditures on chemical renovation. Suckers, northern pike, yellow perch, and minnows are removed from lakes and streams that are reclaimed mainly for cold-water species such as trout, Arctic grayling, and kokanee (lacustrine sockeye).
The first report from Alberta came from the Peace River region (Northwest Area). It stated that only Moonshine Lake had been treated with rotenone to remove suckers, yellow perch, northern pike, walleye, and minnows. There was a good kill of yellow perch, and the pond was restocked with rainbow trout. Trout streams in other parts of the Province were treated with chemicals to remove fish, but fishing did not improve. The second Alberta report came from the Canadian Wildlife Service at Calgary. It was a study of the effects of rotenone on plankton, which showed that some plankters reappeared within 6 months and most of them reappeared within 10 months after the treatment. These findings demonstrated that rotenone was less toxic than toxaphene or copper sulfate, but that rotenone's advantages could be diminished through overdosing. Toxaphene and rotenone have been used with equal frequency in the Province.
British Columbia has used toxaphene in most of the lake reclamations attempted since 1956. Although lakes remained toxic for a few years following toxaphene treatment, biologists were not concerned because the light fishing pressure and low cost were considered to be more important factors. Only a few lakes have been treated with rotenone. Thiodan was tried experimentally, but was toxic to plankton and bottom fauna.
Manitoba started to use toxicants on its lakes in 1950 to eradicate native fish and restock with trout and muskellunge. Provincial biologists also participated in the development of lamprey larvicides. Pre- and post-treatment surveys are made, but to date only a small number of lakes have been treated with almost equal use of rotenone and toxaphene. Some re-establishment of native fish has been detected in a few of the lakes by follow-up surveys.
Two replies from the Fish and Wildlife Branch, Fredericton, New Brunswick indicated that a reclamation program is scheduled for the fall of 1970. The Fisheries Research Board of Canada at St. Andrews, New Brunswick, replied that its program is directed at non-game fishes in ponds and lakes where they dominate over the game fish. The first use of rotenone occurred in 1938 on Potter's Lake. Attempts were made to obtain a selective kill, but the undesirable fish repopulated the lake again, making re-treatment necessary. Usually brook trout have been stocked in the reclaimed waters.
The Province of Newfoundland reported that no reclamations have been performed by the Department of Fisheries and Forestry.
Nova Scotia has had a long history of chemical treatment dating back to 1934 when copper sulfate was used in a 4-year period on four head-water lakes managed for brook trout fisheries. Toxaphene and rotenone have been used also, the latter mainly for selective reclamations. The Department of Lands and Forests Division at Kentville has reclaimed only two lakes, and those in 1961 and 1968. In both cases toxaphene was used very successfully to control white perch. After the lakes detoxified, they were stocked with brook trout. However, toxaphene has been dropped for obvious reasons, i.e., not knowing what its total effect on the environment might be, and the possibility of extended periods of toxicity. In the future, rotenone will be used instead of toxaphene.
Ontario sent four replies, stating that its major efforts center on the control of sea lamprey larvae. Between 1958 and 1968, 106 treatments were made with lampricide in 38 tributaries on the Canadian side of Lake Superior. Eleven streams were treated in Lake Huron. Some estuaries on the Canadian side of Lake Superior have been treated with the heavy-granule formulation of Bayluscide. Prior to 1963, Ontario made equal use of toxaphene and rotenone on inland waters, but in that year it revised the policy on fish toxicants and virtually eliminated the use of toxaphene. Only rotenone can be used in small ponds.
The Yukon Territory's reclamation program is conducted by British Columbia. Because of poor fishing, three lakes were treated between 1960 and 1966 with rotenone or toxaphene to eliminate northern pike, resident rainbow, cutthroat, and hybrid trout. A satisfactory sport fishery was re-established in 2 of the 3 lakes treated. Pre- and post-treatment surveys were made in all cases.
Although Quebec and Saskatchewan did not answer the questionnaire, it is known that both have reclamation programs. Quebec has used mostly rotenone since 1934, but has tried toxaphene, endrin, and Thiodan. Saskatchewan first eliminated undesirable fishes by chemical means in 1959. Since then, the vast majority of its lakes have been treated effectively with toxaphene to improve fisheries for trout and other cold-water species.
With the help of the Inland Fishery Resources Branch of FAO, our questionnaire was sent to 84 countries in South America, Africa, Europe, and Asia. The results were good -- 28 countries sent 35 replies of which 20 contained data concerning use of fishery chemicals. The greatest number of responses came from European countries, followed by Asian countries.
The South American countries, Argentina and Columbia, replied to the questionnaire. Argentina has used rotenone to reduce or eliminate competitive or undesirable species so that balanced populations might exist. Columbia stated that no attempts are made to control fish chemically, but expressed an interest in receiving a copy of our review. We note from the literature that Brazil and Uraguay use rotenone, especially Brazil for control of piranhas. Brazilian natives also have used ichthyothereol and its acetate in bait to poison fish in the Amazon River Basin (Cascon et al., 1965). It is known that native plants have been used for centuries to eradicate unwanted fish populations. At present, Indians throughout South America use leaves from the shrub (Clibadium sylvestre), known locally as “cunani”, and containing a polyacetylenic alcohol, to kill fish (Quilliam and Stables, 1968).
The African countries of Ghana, Sudan, and Uganda stated they do not have fishery management problems of this type as yet, nor are they involved in the use of toxicants.
The Division of Fishery Research, Madagascar, reported that some work had been done with toxicants on inland waters. However, chemicals were used only for controlling or harvesting fish. No native fish is regarded as undesirable, because fish are a source of high quality protein.
As the African countries become more involved in pond culture, they may turn to toxicants to control undesirable fish. Such could be the case in Rhodesia where Tilapia melanopleura has had a detrimental effect on shoreline vegetation, other species of fish, and aquatic birds. Although Nigeria did not respond to the questionnaire, an FAO bibliography cited a work which mentioned the use of plants in that country to poison fish in the Kainji River. In addition, Hickling (1962) reported that rotenone is used in East Africa for the same purpose.
Among the European countries answering the questionnaire, Bulgaria, Cyprus, Italy, Malta, Netherlands, and Poland have not employed toxicants to remove undesirable fish. Cyprus, however, may face such a problem in the future because several fresh-water species have been imported. Malta hasn't imported any fish because there are no lakes, ponds, or streams which can be utilized for fish culture. The Netherlands reported that, as far as is known, no chemical control has been tried. Undesirable fish can be removed from ponds by draining, and the rivers and lakes generally do not contain aggregations of undesirable species that would allow the use of non-selective toxicants. The respondent since has sent an urgent request to us for data on antimycin, a toxicant that can be used selectively.
The Scandinavian countries have had reclamation programs for some time, whereas other European countries have been fairly hesitant to use toxicants until recently. Finland has used rotenone since 1960 in an attempt to eliminate native fish stocks, and has restocked with brown and rainbow trout. An ambitious program has ensued with over 100 lakes treated to date. Denmark submitted three publications on rotenone which is used on a small scale, and only under strictly controlled conditions. Because of costs, only small bodies of water are treated. In one study, rotenone successfully eliminated unwanted fish populations in a peat pit that produces crayfish.
The United Kingdom reported that it was illegal to use toxicants on fish until 1965. The law was changed thereafter, making it possible to apply fish toxicants for certain fishery or scientific purposes. A person or organization must obtain a permit to treat waters chemically, and once having applied the toxicant, is held responsible if anything should go wrong. Rotenone has been the only toxicant applied in 15 operations to date (April 1970), with successful results where non-salmonid fishes were removed from trout waters.
Ireland started 10 years ago to control undesirable fishes with rotenone. Since then complete treatments have become a matter of routine on small lakes to control predators or competitors of trout. Spot-treatments are done on large trout lakes to reduce selectively the fry of northern pike and European perch. The procedures followed include definition of the problem, pre-treatment survey, post-treatment survey, and management follow=up.
In the Federal Republic of Germany, chemical removal of fish is illegal except in private ponds. Experimental applications of toxaphene or Thiodan have been made in lakes, but the investigators are very hesitant regarding toxicants. Hungary stated that there is no program for chemical removal of fish, but ammonium chloride (sal ammoniac) had been tried to control the brown bullhead. Yugoslavia has used rotenone only on a limited scale, and conducted studies on the effects of the toxicant on aquatic fauna.
European countries that did not respond to the questionnaire, but which are known to have used fish toxicants, include Czechoslovakia, Sweden, and Union of Soviet Socialist Republics. Czechoslovakia has applied toxaphene in rivers at least since 1966. Sweden has completed many treatments of lakes and studies with rotenone since the 1950's. Russia also has had a great interest in piscicides, using polychlorpinene to treat 241 lakes with a total of more than 17,000 ha (42,000 a) from 1959 through 1964 (Burmakin, 1967). The reclaimed lakes are stocked with either landlocked or anadromous fishes.
The Southwestern Asian countries have great potential for developing aquaculture. India already has a growing aquaculture and a keen interest in controlling fish populations. Investigators have experimented with many types of toxicants including native plants, of which rotenone is one, phosphamidon, endrin, anhydrous ammonia, DDVP, thiometon, DDT, nicotine, and turpentine (Bhuyan, 1967; George, 1970 and Konar, 1967, 1969 and 1970). Rivers are treated, but not as extensively as ponds. Air-breathing species of fish such as the climbing perch are quite troublesome, and many chemical treatments are made to remove these fish. One respondent reported that ammonia has been used successfully to remove undesirable fishes in small-scale field trials.
The reply from Ceylon indicated that marine animals cause more problems there than do fresh-water fishes. Porpoises and bi-valves create problems, but no attempt has been made to remove them chemically. No fresh-water fish is considered undesirable. West Pakistan has made no attempts to reclaim waters with chemicals. FAO provided information that Iraq has used malathion to stop wild fishes from entering the water supply in which carp are grown.
Among the Eastern and Southeastern Asian countries, Korea stated that it has not attempted to remove fish with toxicants. Japan had no reports on chemical removal of fish; however, several authors had studied the toxicity of endrin to fish. In addition, at least one compound has been considered for chemical fish control -- callicarpone - a chemical used by the natives of Palau and the Philippine Islands. It is highly toxic and is derived from a shrub which grows throughout the South Pacific Islands and Southeast Asia.
Papua and New Guinea related that they never have had a serious fish problem that required chemical treatment. A minor problem has been the control of tilapia in ponds, but this basically has been overcome by drainage or use of copper sulfate. Fishery managers are generally reluctant to use toxicants which could kill fish outside the area cleared. However, local fishermen and museum collectors do use rotenone for collecting fish, but not for controlling fish populations.
The Philippines have not published reports on activities to remove fish chemically because too many individuals employ chemicals to the detriment of the fishery. Several toxicants have been applied in the past 10 years. Endrin is used most to remove pests before stocking milkfish, but investigators are worried about its degradation. Prior to endrin, balls of sodium cyanide were applied in milkfish ponds, but they were expensive, dangerous, and often unavailable. Other toxicants tried include rotenone and nicotine.
Taiwan employs saponin and other toxicants, such as justicidin A and B, to control predaceous fishes in milkfish ponds if screens do not prevent their entering (Lin, 1968 and Ohta et al., 1969).
In response to a request from us, FAO cited a document concerning the use of endrin in Malaya to rid waters of predatory fishes (snakehead and the labyrinthic catfish, Clarias batrachus) before restocking with desirable species. Saponin and rotenone are used, but not in the quantities that endrin is, because of the latter's economy and effectiveness. Other references available indicated that China, Indonesia, and Thailand also use saponin because it kills fish, but not shrimp, in shrimp culture ponds. This toxicant, available in tea-seed cakes, has figured for many years in treatments of rivers, estuaries, and ponds.
With the cooperation of the Federal Research Board for Fisheries and the Food and Agriculture Organization of the United Nations, the German Foundation for Developing Countries (1969) promoted fisheries in Southeast Asia. One of the recommendations made by the 1968 seminar involved toxicants, especially rotenone, to stupefy fish to prevent them from evading fishermen. The other recommendation concerned tea-seed cake to kill or repel carnivorous fish from shrimp ponds. The shrimp are not affected if the concentration is low enough.
In conclusion, the countries in Europe and Asia, more so than the countries in Africa and South America, have fishery programs that include chemical applications as part of their management policies. There has been a recent awareness that the extensive use of certain compounds, which are persistent in the environment, could cause ecological problems. Previously, the main concern had been for the cost of the chemicals, not their over-all effects.
