The freshwater bivalves (Mollusca: Order Unionoida) are classified in six families and about 165 genera worldwide. Worldwide rate of extinction of freshwater bivalves is poorly understood at this time. The North American freshwater fauna north of Mexico is represented by 297 taxa in two families. There are 19 taxa presumed extinct, 44 species listed or proposed as federally endangered, and there are another 69 species that may be endangered. A number of these endangered species are functionally extinct (individuals of a species surviving but not reproducing). Extinction of North American unionoid bivalves can be traced to impoundment and inundation of riffle habitat in major rivers such as the Ohio, Tennessee and Cumberland and Mobile Bay Basin. Damming resulted in the local loss of the bivalves' host fish. This loss of the obligate host fish, coupled with increased siltation, and various types of industrial and domestic pollution have resulted in the rapid decline in the unionoid bivalve fauna in North America. Freshwater communities in Europe have experienced numerous problems, some local unionoid populations have been extirpated, but no unionoid species are extinct. Three taxa from Israel are now reported as extinct. Other nations such as China that have problems with soil erosion and industrial pollution or have numerous dams on some of the rivers (e.g. South America: Rio Parana) are probably experiencing problems of local extirpation if not the extinction of their endemic freshwater bivalve fauna

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.

Results from a 1995 survey of utility company biologists indicate that aquatic biodiversity is an emerging and poorly understood issue. As a result, there is some confusion about what aquatic biodiverstiy actually is, and how we can best conserve it. Only one fourth (24%) of the respondents said their company has a stated environmental policy that addresses biodiversity. Many respondents indicate that over the years they have not specifically managed for biodiversity, but have been doing that though their efforts to assure balanced indigenous populations. While regulations are still the major driver for biological work, an increasing number of companies are involved in voluntary partnerships in managing water resources. Of these voluntary partnerships, 70% have biodiversity as a goal. Biodiversity is becoming an increasingly common subject of study, and a vast majority (75%) of the respondents suggested it should be a goal for utility resource management. Conservation of aquatic biodiversity is a complex task, and to date most aquatic efforts have been directed toward fish and macroinvertebrates. Ecological research and technological development performed by the utility industry have resulted in a number of successful biopreservation and biorestoration success stories. A common theme to preserving or enhancing aquatic biodiversity is preserving aquatic habitat. Increasingly, ecosystem management is touted as the most likely approach to achieve success in preserving aquatic biodiversity. Several utilities are conducting progressive work in implementing ecosystem management. This paper presents the potential interactions between power plants and biodiversity, an overview of aquatic biodiversity preservation efforts within the electric utility industry, more detail on the results of the survey, and recent initiatives in ecosystem management.

The extensive ecological degradation and loss of biological diversity resulting from river exploitation is eliciting widespread concern for conservation and restoration of healthy river ecosystems. Current management approaches often fail to recognize the fundamental scientific principle that the integrity of flowing water systems depends largely on their natural dynamic character, i.e. the natural flow regime. This natural flow regime varies on a wide range of time scales and includes five critical components: magnitude, frequency, duration, timing, and rate of change of hydrologic conditions. Together, these components can characterize the entire range of flows and specific hydrologic phenomena. Human alteration of the natural hydrologic processes disrupts the dynamic equilibrium of a river. Dams are among the most obvious and prevalent disruptions. Effects of this disruption are not only physical, but ecological in nature. Recent management approaches have taken into account the flow needs of only a few specific economically or recreationally important species. Furthermore, these approaches have focused solely on "minimum flow" requirements for a given system. The authors argue that implementation of a more sophisticated assessment of the needs of the river system, in the form of the Instream Flow Incremental Methodology (IFIM), will allow for management plans to move towards a natural flow regime that is beneficial for the entire ecosystem, not simply high profile species. Examples and suggestions as to implementation of these types of management strategies are given.

There is a highly polarized environment in which decisions balancing protection of fish populations and energy generation are made. Hydroelectric power accounts for 12% of U.S. electric supply and virtually all the nation's renewable enrage capacity. Yet, hydro is under increasing attack on environmental grounds, mostly for inputs on fish populations. The 1992 listing of sockeye salmon as endangered has intensified a long-running battle over restoring fish runs and sent mitigation costs skyrocketing. Further complicating the regulatory picture, a Supreme Court decision this spring appears to allow states to set minimum flows at hydroelectric facilities under the authority of the Clean Water Act. The real challenge for applied ecologists will continue to be: how best to put the right information on the table, in the right form, and at the right time to best incorporate ecological consequences in the decision making process.

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.

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.

In this article, I describe the importance of large river-floodplain ecosystems and some of the consequences of altering their natural processes, functions, and connectivity. Then I contrast the species-focused management typically employed by natural rescue agencies with the ecosystem approach. I define ecosystem management as working with the natural driving forces and variability in these ecosystems with the goal of maintaining or recovering biological integrity. I focus on flood pulses both because they drive these systems and because the great floods of 1993-1994 in Asia, Europe, and North America heightened public awareness, thereby creating an opportunity to change river management policies.
I draw my examples largely from the upper Mississippi River and Illinois River because I am most familiar with them. They also exemplify both the conflicts between development and conservation of large floodplain rivers that have occurred world wide and the more recent restoration and rehabilitation efforts that are beginning in Europe and the United States.
The Mississippi River and Illinois River comprise the Upper Mississippi River System, which the US congress designated as both a "nationally significant ecosystem" as well as a "nationally significant waterway" in the Water Resources Development Act of 1986.Plans for even greater expansion of navigation capacity are currently being developed by the US Army Corps of Engineers. But federal and state natural resource agencies and several environmental groups fear that the integrity of the upper Mississippi is being compromised. They have issued their own strategies and plans for conserving and restoring the river.