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increasingly important topic. MAN-MADE ALTERATIONS OF AQUATIC ENVIRONMENTS Man has disrupted, modified, or de- stroyed aquatic and riparian ecosystems in the United States through the following activities: agricultural practices, chan- nelization of streams, dams, dredging, grazing, industrial needs, logging, mining, and urbanization. All of these activities have affected the basic requirements of fish - namely cover, food, and areas for reproduction. Although these activities are the causes of alterations to aquatic systems, this paper will concentrate on the effects of such activities - i.e., (1) the disruption of natural watersheds; (2) alter- ation of streamflows and water temperature; and (3) changes in water quality by increas- ing pollution such as sedimentation. Watershed Management All land use practices on any water- shed affect the water in the drainage basin. Logging practices in the headwaters of a watershed, livestock grazing on the slopes, road construction either on the slopes or in the valley, flood control, recreational use of the land, agricultural- irrigation practices, mining, and pollution from industry and urban expansion can ad- versely affect aquatic organisms or their habitat. In fact, any upstream use or al- teration will have some effect on water downstream. Since stream systems ultimate- ly culminate in estuaries, estuaries are perhaps the most abused aquatic environments and the most difficult to manage because of the multitude of factors that affect these important habitats for fish and wildlife (McHugh 1966; Neusom 1968; U.S. Fish and Wildlife Service 1971). Each ~f the acti- vities that cause alterations to the aquatic environments will be concisely s~arized to provide an overview of the problem. Logging Forests were used for timber and for- age for years in the United States and in- creasing demands for these commodities competed with other uses such as water and recreation (Krygier and Hall 1971). The detrimental effects of logging and associ- ated land-use practices on freshwater and anadromous fish populations has been well documented (Burns 1972; Douglas and See- horn 1974; Eschner and Lon 1963; Gibbons and Salo 1973; Hall and Lantz 1969: Lynch et al. 1977; Moring and Lantz 1975; Moring 1975a, 1975b; Reed and Elliot 1972). Water quality was often degraded during logging by: (1) increasin'g the sediment load as well as the application of pesticides, her- bicides and fertilizers; (2) accumulation of organic debris which reduces dissolved oxygen; (3) water temperatures were increas- 2d after clearing of the trees; and (4) 3treamflows were altered. The various in- teractions of wildlife and forest practices in the Pacific Northwest were covered in a 1968 symposium (Black 1969). Certain fish populations responded according to the type of forest practice in the Pacific Northwest. Cutthroat trout (Salmo clarki) populations were significantly reduced in a stream after a watershed was entirely clearcut (Fig. 1; Lantz 1976). At the same time, cutthroat trout in streams from an un logged watershed and from a watershed that was partially log- ged were not affected (Hall and Lantz 1969; Moring and Lantz 1975). Coho salmon (Oncor- hynchus kisutch) populations in these same streams were not adversely affected; in fact, the biomass and net production of coho salmon increased in the two streams in which the wa- tersheds were logged (Moring and Lantz 1975). The response of fish populations to logging practices has been best documented for the Northwest (Gibbons and Salo 1973) where log- ging is a principle industry, but the im- pacts or forest management practices have also been documented for other parts of the United States (Douglas and Seehorn 1974; Es- chner and Lon 1963). The effects of the practices and the responses of the fish popu- lations are dependent upon the climatic con- ditions of the area, the geology and topogra- phy of the area, the type and extent of the logging practice, and the species of fish that are affected. Grazing As the American bison herds were exter- minated by the pioneers in the western United States, livestock grazing became one of the first major industries in this part of the co~ntry. By the late l800's~ the deteriora- tion of ranges was recognized throughout the west (Box 1977). The intensity of livestock grazing on public lands has been reduced con- siderably between 1935 and 1972 (33,573 to 1~,308 AUM's) with the result that 58% of the public ranges were considered to be in poor copdition in 1935, but this percentage had been reduced to 32% by 1972 (Box 1977). How- ever, Box stated that good to excellent rang- eschave not changed very much between 1935 and 1972. Smith et al. (1967) described a system of rotation grazing on the Big Horn Mountains of Wyoming. Although this type of grazing is being advocated in the western United States, little information is avail- able on infiltration rates, runoff, sediment production, and water quality for the differ- ent grazing practices (Gifford and Hawkins 1976). A recent seminar related to the improvement of fish and wildlife benefits in range management (Townsend and Smith 1977) is noteworthy in that it contains very little information concerning the im- pacts of livestock grazing on aquatic ecg- systems. The lack of quantative informa- tion concerning the impacts of livestock grazing was reported by Platts and Meehan (1977) who emphasized the urgency for this information in making decisions regarding grazing practices. The sociological and economical implications of the livestock industry in many rural western communities are tremendous and will have to be care- fully considered along with other uses of 58