Migratory bull trout ( Salvelinus confluentus ) historically spawned in tributaries of the Clark Fork River, Montana and inhabited Lake Pend Oreille as subadult and adult fish. However, in 1952 Cabinet Gorge Dam was constructed without fish passage facilities disrupting the connectivity of this system. Since the construction of this dam, bull trout populations in upstream tributaries have been in decline. Each year adult bull trout return to the base of Cabinet Gorge Dam when most migratory bull trout begin their spawning migration. However, the origin of these fish is uncertain. We used eight microsatellite loci to compare bull trout collected at the base of Cabinet Gorge Dam to fish sampled from both above and further downstream from the dam. Our data indicate that Cabinet Gorge bull trout are most likely individuals that hatched in above-dam tributaries, reared in Lake Pend Oreille, and could not return to their natal tributaries to spawn. This suggests that the risk of outbreeding depression associated with passing adults over dams in the Clark Fork system is minimal compared to the potential genetic and demographic benefits to populations located above the dams.
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.
The Maryland Fish Passage Program's purpose is to restore migratory species to at or near historic levels. There are four major program elements: remove or bypass blockages, reintroduce target species, bio-monitor and educate. The Program has become increasingly more complex since its inception. Much more is known technically than was known several years ago. Funding has become more difficult to obtain, and legal and policy issues are much more complicated that in the early days of the program. As larger blockage sites are remedied, the Program is increasingly turning its attention to smaller blockages, which are the focus of this workshop. Small blockages are far more numerous than the larger ones, and collectively, they close many more miles of historic spawning habitat to migratory fishes and other aquatic animals than do the larger blockages.
Currently, there are forty-four sites on the five year fish passage project priority list. The list is dynamic. There are additions and deletions as new information is learned about specific stream blockage structures and as funding levels change.
In order to consolidate and unify data related to the many blockages, a fish passage database containing nearly 1,000 blockage sites and 47 fields has been developed and is available upon request.
There are similar issues to contend with at privately owned blockage sites. On occasion it is even difficult to determine the ownership of a blockage. Individuals in Florida, Tennessee and California were contacted to find out who actually owns one priority site. Another site is owned by foreign investors who live in Hong Kong and were located in Australia.
We studied the role of technical clarity in successful multi-party negotiations. Our investigations involved in-depth interviews with individuals who were the principal participants in six consultations conducted under the Federal Energy Regulatory Commission's (FERC) hydroelectric power project licensing process. Technical clarity was especially important in the cases we studied because they concerned questions that were science-based. The principal issues in the six cases were fish passage, instream flow for fish habitat, and entrainment of fish in hydropower turbines. We concluded that technical clarity was one of the most critical elements in these conflicts. The most successful negotiations were marked by a shared understanding of technical issues among the parties.