How Dams Affect Salmon Migration
The 1,000 plus species of Salmon and Steelhead that live off the western coast of the United States and breed in the rivers and tributaries of California, Washington, and Oregon have greatly fallen in population. 106 species have become extinct and 314 more are at risk of extinction in the Columbia River Basin, the focus of this report. The causes of this are dams on the rivers stopping salmon from breeding and smolt from returning to the ocean, and commercial fishing boats depleting mature populations and blocking river mouths. The solution to commercial fishing problems is obvious, though not likely to happen,as the government won't go farther than lightly regulating commercial fishing boats, but there are several different approaches to allowing the salmon to breed and smolt to return to the ocean despite the dams, though no effective measures have been implemented due to cost or effects on energy and agriculture. Also, more recently, escaped Atlantic Salmon from aquaculture cages and their offspring are now competing with the native salmon. How depleted are native salmon and Steelhead populations, what has been done so far to boost the populations and has it been effective, and what can be done with dammed river to allow
For thousands of years the Columbia River was just that, a river. Now we have changed all that by adding huge dams. Today, what was once the wild and vibrant Columbia river, is just a series of slow, warm lakes. This is not the natural habitat of the pacific northwest salmon that once filled the river. The change in the Columbia River from a fast flowing river into still ponds has affected the salmon in three major ways. The first way is by changing the temperature of the river and streams inhabited by the salmon. Because the water is no longer moving at the same speed it once did and instead is at a virtual stand still, the water is allowed to be warmed up by the sun. Salmon smolts are very susceptible to heat and often the temperatures in the streams reach lethal levels. The second problem created by damming the rivers and impeding the flow, is that the smolts now have an even tougher time migrating downstream. The smolt used to be able to use the "flow" of the river to help them reach the ocean quickly and safely. Now, because there is no "flow" up to 90% of the juvenile salmon are killed even before they reach the ocean due to their extended exposure to predators, stress, disease, and other conditions created by dams.The third effect that the slowing of the river has on salmon is that the flow velocity is so slow that the young salmon are unable to reach the sea in time for their change from fresh to salt water fish. The migration that normally takes one week, now takes six. The salmon are forced to live in the fresh water even after they have undergone their physiological changes that help them survive in the e fresh water, and then later in salt water. This change effects there color and aids them in hiding from predators. This means that the salmon are stuck in fresh water without the protective camouflage to fit the rivers, but instead have the coloring to hide in the ocean. Bypass entrance should provide smooth transition to the screens. The screens should then direct fish into areas with a low concentration of predators. However, predation often occurrs in the bypass itself. The concentration of jeuvenile fish is an attractive feast for hungary predators. Par, the stage of salmon development before smolt, have underdeveloped float bladders making them less boyant. As a result of this they travel at lower verticle depths slipping underneath turbine intake screens. Effectivness at each dam varies but they all run into the same basic problems. Debris gets stuck in the thrashbacks and screens. In small mesh screens, algae often causes clogging. Damage often happens when dead trees and large objects bang into equipment. To increase the lifespan of the mechanical equipment, guards are installed. The screens also need protection from ice in the colder months. The Colombia River system is stitched with hydroelectric dams that produce the countries cheapest power, 40 percent cheaper than the national average. This cheap electricity is why most people are overlooking the salmon runs that are rapidly decreasing. Long-term preservation
Some common words found in the essay are:
Columbia River, Pacific Northwest, Dam Marked, Colombia River, River Basin, Fisheries Service, Atlantic Salmon, Smithsonian Institute, Corps Engineers, Washington Oregon, columbia river, pacific northwest, fresh water, salmon steelhead, salmon runs, native salmon, commercial fishing, hydroelectric dams, northwest salmon, turbine intakes, pacific northwest salmon, commercial fishing boats,
Approximate Word count = 2066
Approximate Pages = 8 (250 words per page double spaced)
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