Glenn F. Cada

Fish migration, dams, and loss of ecosystem services in the Mekong Basin.

The past decade has seen increased international recognition of the importance of the services provided by natural ecosystems. It is unclear however whether such international awareness will lead to improved environmental management in many regions. We explore this issue by examining the specific case of fish migration and dams on the Mekong river. We determine that dams on the Mekong mainstem and major tributaries will have a major impact on the basin’s fisheries and the people who depend upon them for food and income. We find no evidence that current moves towards dam construction will stop, and consider two scenarios for the future of the fisheries and other ecosystems of the basin. We conclude that major investment is required in innovative technology to reduce the loss of ecosystem services, and alternative livelihood strategies to cope with the losses that do occur.

The development of advanced hydroelectric turbines to improve fish passage survival

Abstract Recent efforts to improve the survival of hydroelectric turbine-passed juvenile fish have explored modifications to both operation and design of the turbines. Much of this research is being carried out by power producers in the Columbia River basin (U.S. Army Corps of Engineers and the public utility districts), while the development of low-impact turbines is being pursued on a national scale by the U.S. Department of Energy. Fisheries managers are involved in all aspects of these efforts. Advanced versions of conventional Kaplan turbines are being installed and tested in the Columbia River basin, and a pilot scale version of a novel turbine concept is undergoing laboratory testing. Field studies in the last few years have shown that improvements in the design of conventional turbines have increased the survival of juvenile fish. There is still much to be learned about the causes and extent of injuries in the turbine system (including the draft tube and tailrace), as well as the significance of i...

Potential Impacts of Hydrokinetic and Wave Energy Conversion Technologies on Aquatic Environments

Abstract A new generation of hydropower technologies, the kinetic hydro and wave energy conversion devices, offers the possibility of generating electricity from the movements of water, without the need for dams and diversions. The Energy Policy Act of 2005 encouraged the development of these sources of renewable energy in the United States, and there is growing interest in deploying them globally. The technologies that would extract electricity from free-flowing streams, estuaries, and oceans have not been widely tested. Consequently, the U.S. Department of Energy convened a workshop to (1) identify the varieties of hydrokinetic energy and wave energy conversion devices and their stages of development, (2) identify where these technologies can best operate, (3) identify the potential environmental issues associated with these technologies and possible mitigation measures, and (4) develop a list of research needs and/or practical solutions to address unresolved environmental issues. We review the results ...

Evidence of Food Limitation of Rainbow and Brown Trout in Southern Appalachian Soft‐Water Streams

Abstract Seasonal patterns of age-specific growth rates and condition factors of rainbow trout Salmo gairdneri and brown trout S. trutta were studied in relation to the available food resources in five streams of the southern Appalachian mountains. Standing crops of benthic invertebrates were low relative to streams of similar size in other geographic areas. Although terrestrial organisms contributed substantially to the invertebrate drift, total drift rates were also relatively low. Numbers of prey items per trout stomach were small and were directly related to drift rate. These results reflected the limited food base. Condition factors (weight˙length-3) of age- 1 trout declined during summer, and growth rates among age-1 and older trout were generally lower in summer than in winter, despite favorable summer water temperatures. This “inverted” seasonal pattern of growth was likely due to an inadequate food base. We believe that growth rates were relatively low in summer because much of the limited energy...

Distribution and Stability of Potential Salmonid Spawning Gravels in Steep Boulder-Bed Streams of the Eastern Sierra Nevada

Abstract High-gradient boulder-bed streams have been the sites of relatively few studies of salmonid spawning habitat, although they have geomorphic and hydraulic characteristics—and therefore gravel distributions—that are quite different from the more commonly described lowergradient channels. We documented gravel distribution in seven high-gradient stream reaches in the eastern Sierra Nevada. Gravels occurred only in locations characterized by relatively low shear stress; they formed small pockets in sites of flow divergence and larger deposits upstream of natural hydraulic controls. In 1986 (a wet year), all tracer gravels placed in gravel pockets at nine sites on four streams were completely swept away, and substantial scour, fill, and other channel changes occurred at many sites. In 1987 (a dry year), tracer gravels and the channel cross sections were generally stable. Periodic mobility of gravel may explain why brown trout Salmo trutta are more abundant than rainbow trout Oncorhynchus mykiss in the ...

A Review of Studies Relating to the Effects of Propeller-Type Turbine Passage on Fish Early Life Stages

Abstract Although few studies have been conducted to directly quantify ichthyoplankton mortality at hydroelectric installations, there is a considerable body of literature on examinations of the various stresses (i.e., pressure changes, blade contact, shear) that could affect turbine-entrained eggs and larvae. A review of these studies suggests that turbine-passage mortality of early life stages of fish normally would be relatively low at the low-head, propeller-type turbine installations (e.g., bulb or STRAFLO turbines), for which relevant design information is available. The shear forces and pressure changes in low-head bulb turbines are unlikely to cause ichthyoplankton mortality. Probability of contact with turbine blades is related to size of the fish; less than 5% of entrained ichthyoplankton would be affected. Potential additional sources of mortality related to the design and operation of hydroelectric facilities, and thus mitigable, include withdrawal of deep water and cavitation.

Survival Estimates for Juvenile Fish Subjected to a Laboratory-Generated Shear Environment

Abstract Juvenile rainbow trout Oncorhynchus mykiss and steelhead (anadromous rainbow trout), fall (age-0 and age-1) and spring Chinook salmon O. tshawytscha, and American shad Alosa sapidissima were exposed to shear environments in the laboratory to establish injury–mortality thresholds based on estimates of strain rate. Fish were exposed to a submerged jet having exit velocities of 0 to 21.3 m/s, providing estimated exposure strain rates up to 1,185/s. Turbulence intensity in the area of the jet where fish were subjected to shear was minimal, varying from 3% to 6% of the estimated exposure strain rate. Injuries and mortalities increased for all species of fish at strain rates greater than 495/s. American shad were the most susceptible to injury after being subjected headfirst to a shear environment, while steelhead and rainbow trout were the most resistant. There was no apparent size-related trend in susceptibility to high shear except that age-0 fall Chinook salmon were more resistant to shear environm...

Effects of Repeated Electroshocking on Instantaneous Growth of Trout

Abstract Instantaneous growth rates were calculated for age-1, -2, and -3 + wild rainbow trout (Salmo gairdneri) and brown trout (Salmo trutta) at each of eight stream sites on five streams in western North Carolina and eastern Tennessee. Growth rates of individual trout that had been electroshocked with pulsed DC two to seven times within a 12-month period were lower than the average growth rates for trout of the same age and species at their respective sites. This decrease in growth rate occurred significantly more often among age-1 and -2 trout than among those 3 years and older, and more often among trout that had been electroshocked within the last 2.5 months than among trout that had 3 or more months to recover from electroshocking. These results indicated that fisheries management studies should be designed to avoid repeated electroshocking, especially at intervals of less than 3 months. Growth studies in which more than a small fraction (e.g., >20%) of the total population is repeatedly electrosho...

Status of Fish Passage Facilities at Nonfederal Hydropower Projects

Abstract The status of direct mitigation practices for fish passage was assessed as part of an ongoing, multi-year study of the costs and benefits of environmental mitigation measures at nonfederal hydroelectric power plants. Information was obtained from the Federal Energy Regulatory Commission, hydropower developers and state and federal resource agencies involved in hydropower regulation. Fish ladders were found to be the most common means of passing fish upstream; elevators/lifts were less common, but their use appears to be increasing. A wide variety of mitigative measures, including spill flows, narrow-mesh intake screens, angled bar racks and light- or sound-based guidance measures, is employed to prevent fish from being drawn into turbine intakes. Performance monitoring and detailed, quantifiable performance criteria were frequently lacking. Fifty-two of the 66 projects (82%) with operating downstream fish passage measures had no performance monitoring requirements; 50 of 71 project operators (70%...

Effects of water velocity on the survival of downstream‐migrating juvenile salmon and steelhead: A review with emphasis on the Columbia river basin

Abstract Restoration of salmon and steelhead stocks in the Columbia River Basin depends in large part on the adequacy of streamflows needed to transport juveniles safely downstream to the ocean through a series of dams and reservoirs. Compared with preimpoundment conditions, lower spring and summer river flows and decreased water velocities are believed to increase juvenile salmonid travel times to the ocean, and potentially to reduce survival. Because of continuing disagreement about the quantities of flow releases needed to increase smolt survival, we reviewed literature from within and outside of the Columbia River Basin relating to the influence of water velocity on the survival of juvenile salmon and steelhead. Most of the studies reviewed found a positive relationship between outmigration flows and survival, but there is substantial uncertainty about many of the estimates. Early survival estimates made in the basin did not quantify variance and contain biases, errors, or reflect interactions with fa...