Factors Causing Salmon Decline:
|Problem||Dams||Logging|| Changing |
|Agriculture||Pop. Growth||Over Fishing||Other|
|Salmon Migration Barriers||Big Time||no||no||no||no||no||no|
|Barriers to Reaching Spawing Grounds||Yes||no||Yes||no||no||Yes!||no|
|Reduced Number of Young Salmon reaching sea||yes||yes||no||no||no||no||bird|
|Industrial Pollutants Exposure||no||no||no||no||Yes||no||no|
|Loss of Streamside Vegetation and Functions||no||Yes||no||Yes||Yes||no||no|
|Increased Sediment Load||no||Yes||Yes||Yes||Yes||no||no|
|Natural Habitat Destruction||yes||yes||no||yes||yes||no||no|
|Reduced Fresh Water Flow in Rivers and Streams||yes||no||no||yes||yes||no||no|
|Abnormal water temperatures||yes||no||yes||yes||no||no||no|
|Reduced upwelling and nutrient/food supply||no||no||yes||no||no||no||competition with hatchery fish|
|Loss of cool deep pools in streams||no||Yes||no||no||no||no||no|
Evidence of a Nutrient Deficit in the Freshwater Systems of the Pacific Northwest. A comparison of historic and current levels of salmon abundance was used to determine the current deficit of marine-derived nutrients for Pacific Northwest streams. This nutrient deficit may be one indication of ecosystem failure that has contributed to the downward spiral of salmonid abundance, further diminishign the possibility of salmon population recovery to self-sustaining levels.
This is the raw salmon count data at Boneville Dam that we will inspect more closely below. Evidence of quasi-cylical behavior is apparent. Generating count Data (last year and this year are high!)
Some relevant WWW resources:
Canadian Harvest Increases
Some Salmon Links
This is likely a reflection of where the Salmon are and this is strongly coupled to decadel climate changes in the Alaska-BC-PNW region.
This implies, that at any particular point in this region, over timescales of 50 years, salmon counts/catches will be cyclical in nature.
the poll on tuesday showed that most believed this would *not* be effective. However, many thought it would or didn't know.
Pros and Cons of Dam Breaching:
First we noticed that the listed items under Aguments against are quite obvious and really don't require justification. All of these things would happen, it just matters to which degree they would happen and this is very difficult to model.
So let's concentrate on the other items in the Arguments For column.
The principle hypothesis here is whether or not dams have caused a "catastrophic" loss of population.
We can use salmon count data as a means of establishing a baseline. We can then convolve that data with the following simple model:
X ----------|-------------|--------|------|--------|----|---|--|-> X' 1 2 3 4 5 6 7 8Suppose we have a system where X salmon enter and have to pass 8 dams to reach X'.
The issues are:
Corps of Engineer Estimates
These hypothesis can be tested to some extent by the actual salmon count data which exists at each dam. That data is readily available .
But we aren't doing an indepth analysis here. Let's keep it simple.
Under the model where all dams are equal then we should see something like this in the data.
X1 < X2 < X3 < X4 < X5 < ...
While there are complicating factors, this basic pattern should be defined the data on upstream salmon counts. You will be testing that in your next homework assignment.
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