The RCC, FPC, and RPM are all inadequate for understanding the main channel as a functioning foodweb. The purpose of the paper is to provide data on fish habitat and food preferences in large rivers, connect the main channel's relationship to fish and other habitats, and to describe the main channel foodweb. The studies were carried out on the Illinois River and the Upper Mississippi River.

The Mississippi River is the hardest working river in America: a central artery for commerce, a stormwater management system for the two-thirds of the nation, the central flyway for 40% of the nation's migratory waterfowl. Each of the river's distinct forms of habitat is disappearing: backwater marshes dominated by emergent plants are filling in or, alternatively, becoming open, lifeless turbid waters; floodplain lakes have filled with silt; aquatic plants are not replaced because perpetually turbid waters block light penetration; sediment buries mussel beds and deepwater pools' islands erode, eliminating mast-producing forests. High water tables undermine floodplain forests, which lack higher ground to replace themselves. Restrictions of fish movement by the dams makes the decline of habitat in a particular pool more significant by blocking fish access to habitats in another pool. These problems are exacerbated by current river uses, and by past and present land uses that have altered basinwide hydrology and accelerated the rate at which sediment enters the river. Sediments and nutrients enter the river at unsustainable rates due to past and present land use practices that increase erosion and eliminate wetlands and stream-side buffers. Commercial and recreational vessels resuspend sediments in the water column, blocking light penetration and contributing to the loss of backwaters. Even in its reduced for, the Upper Mississippi represents the last piece of Midwestern America's Great Rivers, supporting migrating waterfowl, endangered mussel species and the most ancient lineage of fish in North America. Whether this system continues to survive and flourish depends on whether dynamic river forces can be sufficiently restored to make the river system self-sustaining. Preserving and restoring the Upper Mississippi and Illinois rivers requires three types of actions: 1. Recreate dynamic river forces to achieve self-sustaining habitat restoration 2. Minimize the operational impacts of the navigation system 3. Achieve no net increase in sediment by 2010

Water of sufficient quality and quantity is critical to all life. Increasing human population and growth of technology require human society to devote more and more attention to protection of adequate supplies of water. Although perception of biological degradation stimulated current state and federal legislation on the quality of water resources, that biological focus was lost in the search for easily measured physical and chemical surrogates. The "fishable and swimmable" goal of the Water Pollution Control Act of 1972 (PL 92-500) and its charge to "restore and maintain" biotic integrity illustrate that law's biological underpinning. Further, the need for operational definitions of terms like "biological integrity" and "unreasonable degradation" and for ecologically sound tools to measure divergence from societal goals have increased interest in biological monitoring. Assessment of water resource quality by sampling biological communities in the field (ambient biological monitoring) is a promising approach that requires expanded use of ecological expertise. One such approach, the Index of Biotic Integrity (IBI), provides a broadly based, multiparameter tool for the assessment of biotic integrity in running waters. IBI based on fish community attributes has now been applied widely in North America. The success of IBI has stimulated the development of similar approaches suing other aquatic taxa. Expanded use of ecological expertise in ambient biological monitoring is essential to the protection of water resources. Ecologists have the expertise to contribute significantly to those programs.

Efforts by a citizen's group, Putah Creek Council, to improve the flow regime of a California stream for ecosystem, aesthetic, recreational, educational, and research purposes led to a successful court trial in which fish conservation played a key role. A major issue around which the trial revolved was the proper interoperation of section (5937) of the California Fish and game Code, which states that fish must be maintained in "good condition" below a dam. We defined good condition to mean there had to be healthy individual fish in healthy populations that were part of healthy biotic communities. This definition resulted in a conceptual model for instream flows for the creek that favored native resident and anadromous fishes. The stream flow recommendations from this model had four components: living space flows for the entire creek, resident native fish spawning and rearing flows, anadromous fish flows, and habitat maintenance flows. The trial judge, in attempting to balance competing demands for the water, ordered the implementation of only the first two recommendations. The order has been appealed by the water interests, but regardless of the final outcome, the court's decision reflects the growing public interest in protecting streams, the need for innovative use of existing legal tools to try and protect aquatic resources, and the importance of biological information in developing flow recommendations for complex fish assemblages.

This paper examines the effects of dam construction and operation in the Columbia River Basin on salmon populations. While the hydrograph of the Columbia River has been significantly impacted by dams, the seasonality of regulated flow on the Snake River has been less affected. The Snake River storage has been used for agricultural diversion while the Columbia has been for electrical generation. The reservoir system has effects on flow velocities, water chemistry (nitrogen supersaturation), habitat availability and reliability, and stream temperatures. Dams block about one third of the Columbia River watershed to access by anadromous fish.
Effects of Dams on Salmon;
Fish kills occur as a result of several characteristics of dams. Bruising, descailing, and stress caused by by-pass facilities; susceptibility to prey following delivery from by-pass to outfall; estuary damage; effects on the homing ability of fish; limited success in fish use of by-pass facilities. The effect of migration speed on smolt survival is uncertain but assumed to have an impact. More research is necessary.
Mitigation of Dam's Effects on Salmon:
Seven measures for mitigation of dams' effects on salmon are discussed
1. Fish passage facilities 2. Predator control 3. Transportation 4. Spill 5. Flow augmentation 6. Reservoir drawdown 7. Dam removal.

Modifications of lower watersheds such as water abstraction, channel modification, land-use changes, nutrient enrichment, and toxic discharge can set off a cascade of events upstream that are often overlooked. This oversight is of particular concern since most rivers are altered by humans in their lower drainages and most published ecological investigations of lotic systems have focused on headwater streams. Factors contributing to ecological processes or biophysical legacies in upper watersheds often go unacknowledged because they occur at disparate geographic locations downstream (e.g., gravel mining, water abstraction, dams) with significant lag times. This paper considers examples of how alterations to streams and rivers in their lower reaches can produce biophysical legacies in upstream reaches on levels from genes to ecosystems. Examples include: 1) genetic- and species-level changes, such as reduced genetic flow and variation in isolated upstream populations; 2) populations-and community-level changes that occur when degraded downstream areas act as population "sinks" for "source" populations of native species upstream or, conversely, as "source" populations of exotic species that migrate upstream; and 3) ecosystem-and landscape-level changes (e.g., nutrient cycling, primary productivity, regional patterns of biodiversity) that can occur in headwater systems as a result of downstream habitat deterioration and hydrologic modifications. Finally, a case study from my own research illustrates the importance of careful consideration of downstream-upstream linkages in formulating research questions, designing experiments, making predictions, and interpreting results. The effects of dams and associated water abstraction in lowland streams of Puerto Rico has forced my colleagues and me to re-evaluate the results of ecological research that we have conducted in highland streams over the past decade and to redirect our research that we have conducted in highland streams over the past decade and to redirect our research to consider downstream-upstream linkages.

This article presents and overview of the hydropower industry and summarizes two recent events that have greatly influenced relicensing and environmental issues. First, the US Supreme Court's May 1994 Tacoma decision raised fundamental questions about who has the authority to relicense hydroelectric power plants. Second, under the Endangered Species Act, Federal agencies are required to ensure that their actions do not jeopardize protected species and their habitat. The impact of the Act has been particularly significant recently for the federally owned facilities in the Pacific Northwest that are presently under streamflow restrictions aimed at aiding endangered local fish populations.

The most often heard claims in support of large scale hydroelectric development are: (1) hydropower generation is 'clean', (2) water flowing freely to the ocean is 'wasted', and (3) local residents (usually aboriginals) will benefit from the development. These three claims are critically examined using case histories from Canada and elsewhere in the world. The critique is based mainly on journal articles and books, material that is readily available to the public, and reveals that the three claims cannot be supported by fact. Nevertheless, large scale hydroelectric development continues on a worldwide basis. The public needs to be well informed about the environmental and social consequences of large scale hydroelectic development in order to narrow the gap between its wishes for environmental protection and what is really occurring.

1. Seventy-two per cent of the Flathead River catchment (22,241 km^2) is federally designated and protected as wilderness or national park. Thus, the catchment remains one of the more pristine areas of its size in the temperate latitudes of the world.
2. Discharge in the downstream reaches of the river system outside the protected areas is regulated by three dams for flood control and hydropower production. These dams have blocked natural migration of native fish from Flathead Lake (496 km^2) and isolated populations in sub-catchments. Temperature and erratic flow fluctuations have altered phenologies of river zoobenthos and fish, and in dam tailwaters aquatic biodiversity is drastically reduced in comparison to unregulated segments.
3. Ecological problems caused by changing water quality conditions, altered land-use patterns and introductions of no-native biota are interactive with the impacts of stream and lake level regulation , thereby emphasizing the complexity of this river-lake ecosystem.
4. Mitigation of the effects of regulation is compromised by differing management priorities and regulatory mandates of County, State, Tribal, and Federal agencies responsible for natural resource management within the catchment. Moreover, economic and ecological interests outside the Flathead influence the way flows are regulated within the catchment.
5. The most pervasive influences of stream and lake regulation can be ameliorated by retrofitting the hypolimnial release dam with a selective depth outlet structure to allow temperature control, and by controlling changes in flow rates to create a more natural hydrograph in the tailwaters of the large dams. Allowing fish passage by construction of fish ladders is problematic because upstream passage will commingle native species that were isolated upstream by construction of the dams with non-native species that were introduced subsequently below the dams. Cascading food web interactions elicited by invasions of non-native biota may offset any advantage to native stocks gained by passage and/or augmentation with hatchery stocks.
6. Mitigation must be adaptive in the sense that unanticipated effects and interactions with other management objectives can be documented and alternative action can be implemented.
7. This case history of the effects of stream and lake level regulation, and the approaches to management reviewed in this paper, should serve as a lesson in river conservation.