Other studies have shown various enemies to salmon and their recovery. Habitat loss and degradation contribute in 91 percent of all cases of salmon mortality. Those dams degrade and destroy Snake River salmon migration habitat. Hybridization, competition, predation and interactions with hatchery produced fish contribute to salmon loss in 53 percent of the cases. Overfishing contributed to salmon loss in 50 percent of the cases.
The listed enemies of salmon and salmon recovery include: mining, logging, agricultural practices, urban development, dams, estuary modification, fishing and artificial propagation of fish from hatcheries and salmon farms bring in disease, weaken genetics and perhaps most importantly mask the decline of wild stocks of fish.
In 1991, Willa Nehlsen, Jack Williams and James Lichatowich (author of Salmon Without Rivers) took perhaps the most important look into the salmon issue in the Columbia River Basin. They found 107 extinct populations and 214 populations in jeopardy.
Man has made 31 percent of formerly available salmon habitat inaccessible through the construction of dams that do not allow fish passage in the Columbia and Snake river basins. Prior to 1850, 14,666 miles of streams in the Columbia/Snake were connected and available for salmon populations. Today, only 10,073 miles remain accessible to our salmon. Within those 10,073 miles of accessible stream, our salmon have to negotiate man-made reservoirs behind eight dams in regards to Snake River salmon and steelhead. Habitat is also degraded by various human activities and also degraded by natural activities influenced greatly by our mistakes in regards to the numerous megafires that have occurred throughout the landscape. Our forests became overgrown tinder boxes and in some cases lightning sparked catastrophic forest fires that have played a role in degrading habitat for salmon and steelhead.
An example of this is along the South Fork of the Salmon River. About 1 million acres of forest burned up in 2007 primarily along the South Fork of the Salmon River. In the summer of 2008, large landslides occurred that sent huge amounts of sediment into the East Fork of the South Fork and the South Fork river. Eventually, this sediment will be washed away and salmon habitat will be restored such as it has been throughout time, but because we were very good at snuffing out forest fires in the 20th century, we inadvertently created overgrown forests ripe for cleansing fires.
Beyond the sediment loads that make the stream shallow, those fires also erased a great deal of the canopy shading the South Fork and many of its tributaries making the overall temperature of the streams higher, which will have a negative effect on salmon and steelhead that return to west central Idaho.
There isn't a lot we can do about that situation now and eventually as the new forest rises it will solve itself.
There are five areas where we can do better for our salmon today. Those areas are 1) breaching the four lower Snake River dams (the most important thing we can do and the only thing that will ensure recovery), 2) limit mining operations within salmon and steelhead watersheds or create ironclad fines that affect a company's bottom line severely if they degrade a salmon or steelhead stream, 3) stop or severely limit the modification of the Columbia River estuary, which is primarily a problem of the US Army Corps of Engineers dredging practices and various manipulations of wildlife populations, 4) pass stricter regulations on various agricultural practices and wastewater treatment that allow various chemical agents into our salmon and steelhead streams that can alter gender to create virtually all male generations of salmon due to these chemicals entering spawning areas and interacting with developing salmon and 5) we need to cut back on our artificial propagation of fish. On that fifth and final point, I would like to see more studies on the fecundity of returning salmon from egg box releases. We know returning hatchery fish when allowed to supplement the natural population have incredibly lower fecundity rates, is this also the case for eyed-egg box plantations? I don't know, but if it is then obviously we shouldn't plant so many egg boxes, but if by planting eggs rather than the more successful survival to smolt rates hatcheries get create adults with similar fecundity rates as our wild fish, I still see a limited future in artificial propagation of salmon and steelhead.
Regardless of the other challenges mentioned above, without breaching the lower four Snake River dams our wild salmon and steelhead will be extinct within my lifetime in the Snake River basin. It begins there, but know there are other things we need to do as well