Fish toxicants are widely used to eradicate some or all of the fish in a body of water in order that desirable fishes can be stocked, free from predation, competition, or other interference by undesirable fishes. The process of eradication and restocking is referred to by various authors as reclamation, rehabilitation, or renovation. We prefer the term reclamation.
General fish toxicants, such as antimycin, rotenone, or saponins, usually are applied to kill all fish in a body of water, although they may be employed for selective kills of fish under special circumstances. Selective toxicants, such as TFM and Squoxin, are used to kill only certain target fishes without harm to other fishes present in the habitat.
A total reclamation has the objective of killing all fishes present in the target area, and it is the more common of the reclamation processes. A partial reclamation usually refers to the poisoning of only that part of a body of water that contains the target species, such as the treatment of the epilimnion of a thermally stratified lake to kill warm-water fishes. Spot-treatment, a variation of partial reclamation, is practiced with a suitable toxicant against localized concentrations of target fish, such as against congregations of spawning carp in a marsh.
A variety of plants having fish-killing properties has been known for centuries, especially in South America and Asia. Many have been employed directly to collect wild fish from ponds and streams for the table. The Chinese, however, have long used plant extracts to destroy undesirable fish in culture ponds. But, it is only within the past 40 years that the practice of reclaiming streams, rivers, ponds, lakes, and reservoirs has grown rapidly, particularly in the United States and Canada. The evolution of new and powerful pesticides in more efficacious formulations has motivated more mono- or bi-species management of food and game fishes in wild and cultured waters. Prévost (1960) stated that the reclamation of waters by poisoning fish is the best available management tool.
We expect that the use of fish toxicants for reclaiming waters will continue to increase because:
1) There is a growing need for intensive management of food and game fishes to meet increasing demands in shrinking water resources.
2) Selective exploitation, unwise stocking of native or exotic fishes, or alterations in water quality are contributing to frequent imbalances in wild populations, with undesirable fishes suppressing or excluding desirable fishes.
3) Improved toxicants, specific to fish, are becoming available.
4) More and better-trained people are entering the field of fishery management.
The causes and instances of fishes in pest situations were discussed in considerable detail by Lennon (1970a and 1970b).
Our review points out some of the problems inherent in the nature or formulation of early fish toxicants. In addition, there were problems with fishery personnel that affected the success of reclamations. Prior to World War II there were serious shortages of trained men and money in fishery management. There were very few fishery biologists then, and most of them worked in fish hatcheries or in fish classification. the few biologists in the field had difficult days, especially in the United States, because many anglers who purchased fishing licenses tended by some strange metamorphosis to become vocal experts on fishery management. Many fishermen debated the need for fishery research when the solutions to problems in fishery management seemed so obvious to them. Furthermore, license fees for sport fishing -- the sole support for most conservation agencies in the United States -- were ridiculously low and inadequate to support vigorous and well=balanced management programs. The situation improved somewhat in the late 1940's, but it wasn't until the United States Congress passed the Dingell-Johnson Act in 1950 that fishery research and management received a badly needed stimulus. Under the Act, the proceeds of a 10-percent Federal excise tax on sport fishing equipment are apportioned annually to the states on a 75:25 matching basis for fishery investigations and management. Thus, the old problem of funding fishery programs was largely solved.
The lack of trained fishery biologists continued to be a problem until 1960 when the United States Congress established and funded the Cooperative Fishery Unit program. Under this program, the U.S. Bureau of Sport fisheries and wildlife cooperates with a state conservation agency and a university within the state to form a cooperative fishery unit at the university, staffed by professional fishery biologists with faculty status. The purpose of a unit is to train fishery biologists, especially at graduate levels, to conduct fishery research, to provide extension-type activities within its area of influence, and to participate in fishery management within the state. By 1970, 23 units were in operation, and 224 investigational projects were in force that year. Graduates of unit programs are contributing significantly to a pool of fishery talent.
Still another handicap has been evident in fishery management. Although biologists in general are increasingly involved in the control of vertebrate pests throughout the world, few schools offer training in the principles and methods of animal control. Hopefully, this handicap is temporary. Its effect, however, has been that many control activities on land and in water were conducted amateurishly, if not dangerously, and too often with deleterious effects on the environment. The increasing potency and sophistication of control chemicals require commensurate competency on the part of biologists using them. The men in the field need academic or in-service training in the means and methods for safe and effective fish control, and they need up-to-date manuals on reclaiming standing and flowing waters.
Much new equipment developed in recent years makes the task of reclaiming waters easier. Airplanes, helicopters, and all-terrain vehicles are used for quick access to waters and for distributing control chemicals. Portable boats and motors have been improved greatly in recent decades. SCUBA gear and underwater television enable previously impossible observations of fish in situ. Sonar and other sensing apparatus expedite the mapping and survey of waters. Lightweight power generators facilitate the use of labor-saving instruments in the field. In general, the biologist today is better able than his predecessors to conduct all-weather, all-season fishery management.
This review of fish toxicants and reclamations was designed to bring together the more pertinent of the past and present information under one cover. The review of literature was divided into three sections: 1) on fish production, farm, and ranch ponds; 2) on lakes and reservoirs; and 3) on streams and rivers. A measure or the current use of fish toxicants was obtained by sending a questionnaire to states and provinces in the United States and Canada and to many countries throughout the world. The responses are summarized in a fourth section. A fifth section includes recommendations on the research required to improve reclamation with toxicants as a management tool.