CAUSES OF SALMON DECLINE There are many causes of the salmon stocks' decline in abundance: dams, water use, overharvest, habitat destruction, hatchery impacts, and other human-induced factors all play roles in reducing the Snake River salmon populations. Ocean conditions have also been a significant factor in the decline of salmon populations, though these natural fluctuations are beyond our control. As noted by the Snake River Recovery Team, no single factor is responsible for the full extent of the decline, and no single action will restore the fish. One of the problems is institutional. There is insufficient focus and accountability to ensure effective management of the overall system for the sake of the salmon. Institutional , jurisdictional, international, state and Federal boundaries make coordinated overall fisheries management decisions difficult. In many of the Snake River salmon watersheds, the problems begin before the salmon emerge from the gravel. Land use activities such as logging, grazing, mining, and road building can smother redds (salmon nests) with silt or sediment. Livestock may step directly on a redd and kill the salmon eggs. Once young salmon emerge from the redds, ecological interaction with hatchery fish such as competition, predation, displacement, and disease transfer contribute to population declines. Logging may eliminate stream side trees which would otherwise fall into the water and create important habitat for salmon. Other land use activities such as moving stream-shading trees, may increase water temperatures to levels that are lethal for juvenile salmon. Livestock grazing often removes vegetation near streams and thereby reduces stream back stability. Once the salmon are ready to migrate to the ocean, they face the problems associated with the hazardous downstream journey. This journey through the lower Snake and Columbia rivers has become more hazardous since eight hydroelectric dams were completed and their reservoirs were created. Seventy percent of the 471 miles from the mouth of the Columbia River to Lewiston/Clarkston on the Snake River has been converted from free-flowing river into reservoirs. Juvenile salmon (called smolts when they are ready to migrate seaward) must find their way through the reservoirs and past the dams. Smolt-to-adult survival rates of Snake River salmon stocks have declined to the point where they equal about one-fourth the rates observed in the 1960s, and migration time for smolts from the Snake River to the Columbia River estuary has doubled. The longer the smolt migration time, the greater the risks of predation and disease. Smolts may pass the dams through different routes, those passing over the spillway or using the bypass systems have higher survival rates than those that pass through the turbines. Improvements in bypass systems at several of the dams are helping to make passage safer for the fish. Before the dams were built, flows in the spring were higher. Historically, even in years of low flow, there was sufficient current to carry the smolts to the sea. Then, as now, most of the smolts migrated at night which might be a way of avoiding predators. Not only did the dams slow the rate of downstream travel for smolts, they increased the amount of habitat favorable to predator species, and provided physical conditions that improved the predators' ability to detect and capture juvenile salmon. Hatchery fish and exotic species which complete with, and prey on, chinook and sockeye have also been introduced into the system. The construction of hundreds of large and small reservoirs has physically altered the original hydrology of the Columbia River Basin. The flows for the lower Snake and Columbia rivers have been changed from natural conditions to those considered more desirable for human uses. A complex management system has been developed to manage the basin's reservoirs and flows. The system was primarily developed to control floods, provide water for irrigation, and serve the hydropower system by storing water for use when power demand is high. Little is known about survival rates of salmon once they enter the Pacific Ocean, but there is growing evidence that survival rates are not uniform from year to year and that variations in ocean productivity may affect stocks over wide geographic areas and time frames. Annual variability and the possibility of long-term trends in the ocean environment make it difficult to detect changes in survival that result from efforts to improve inland conditions. When salmon begin their upstream migration as adults, they face harvest by commercial and recreational fisherman and predation by marine mammals and other animals. Passage through the dams also presents a problem. Biologists are able to count salmon as they use the dams' fish ladders on their way upstream. Large numbers of salmon "disappear" in between dams. The reason these adult fish disappear include: mortality, unreported and illegal harvest, fish falling back over the dams after being counted in the fish ladder of a previous dam, straying or wandering, and spawning in reservoirs and their tributaries. The causes of mortality may include: predation and wounding by marine mammals, injuries from fishing gear, water pollution, high water temperatures, large spillway discharges, and disease. Additional mortality may result from injuries received when the fish "fall back" downstream and go through turbines, bypass systems, spillways, or navigation locks. When the adult salmon return to the area where they emerged from their parents' redd, they again face habitat problems. Spawning beds may be silted in with sediment from logging, mining, or road building, or the water may be too warm for them. In addition, the human activities may unintentionally scare them away from the spawning beds.

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