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338 CHAPTER 14 Cost .......................................... :::::::::::::::::::::::::::::::::::::::::: .:.:.:.:..:.:.:.:.:.:.:.:.:..:.:.:.:.:.:.:.: Size of water .................... .:.:.:.:.:.:.:.:.:.:.:.:.:..:.:.:.:.:.:.: :.:.:.:..:.:.:.:.:.:.:.:..:.:..:.:.:.:..:..:. .................... Water temperature and quality Target species ............... .............. ............... .............. ............... .............. ............... .............. ............... ............... .............. ............... .............. ............... .............. ................ .............. ............... Public opinion ......... .......... ......... .......... ......... .......... ......... .......... Ownership of water ......... .......... ......... .......... ......... .......... ......... .......... ......... location of water Environmental concerns o 5 10 15 20 25 30 PERCENT Figure 14.2 Criteria used to determine method employed to control undesirable fishes. population can result in additional problems. These may include overpopulation and eventual stunting of predator fish or virtual annihilation of forage fish by effective predators. 14.4 CHEMICAL METHODS FOR MANAGING UNDESIRABLE FISH SPECIES Chemical control is the most popular method to control undesirable fishes because of the ease of application, the short time required to achieve lasting results, and lower cost when compared with other control measures. Generally, a complete removal of all fish is the goal of a treatment project, although partial treatments can also be effective. Partial treatments with chemicals include (1) treatment of spawning sites of fish, (2) treatment of particular sections of lakes, or (3) "thinning" of stunted stocks of game fish (Lennon et al. 1970; Bradbury 1986). Partial kills are usually followed by introductions of predatory game fishes to feed on forage species or to control less desirable fishes. Restocking following any chemical treatment should consider available food sources. For example, stocked fish may perform poorly if zooplankton abundance is low. Partial treatments have met with varying success depending on size of the water body treated, water quality, water temperature, and target species (Bradbury 1986). 14.4.1 Properties of an Ideal Fish Toxicant Chemical fish toxicants must have properties that are consistent with the needs of fisheries managers and that meet requirements of government regulations. The toxicant selected should be specific to the species of fish targeted, easy and safe to apply, degrade to harmless constituents in a limited time without the aid of a detoxicant, be harmless to nontarget organisms (plant and animal), be effective over a broad range of water quality conditions, and be registered for use in the aquatic environment (Lennon et al. 1970). No currently registered fish toxicant