The Salmon Decline

ENVS 202 On-line Access


The Decline of the Northwest Salmon?

The apparent decline of the salmon in the Columbia river system is one of the most complex environmental problems we have.

However, this problem has been over-simplified by the media and others to one single root cause, namely the construction of hydroelectric dams on the Columbia river system.

Today we wish to access of this simplification is valid. The homework assignment given will allow you to explore this issue in more depth as well. For today we want to examine some of the broader issues and look at the actual data which is available.

The Salmon controversy is an excellent example of arguments made largely on belief, instead of knowledge that is supported by the actual data .

It is also an excellent example/reflection of another problem that effectively prohibits meaningful discourse; reactive vs proactive positions

Factors Causing Salmon Decline:

Broad Brush Factors:

  1. Dam Construction
  2. Increased Logging
  3. Changing climate patterns
  4. Agriculture
  5. Increased population growth
  6. Over fishing

More Detailed Factors in relation to Above:

Let's look at some data. Most of this data comes from fish counts done at Bonneville Dam starting in 1938 (again the next homework assignment will have you make use of this data):

Blue line represents growth of non-harvested fish in the Columbia River system. The implication is that competition for food/nutrients is increasing rapidly.

Its getting warmer earlier in the season with time in the Columbia river. Is this cause local (e.g. dams/ag) or global (e.g. Global Warming)

Graph shows harvesting by Tribal communities with protected fishing rights. Some degree of "over harvesting" is apparent.

Graph shows total salmon catch off the coast of North America (including Alaska).

Decline of In-River catches which is frequently used as the "best" indicator for overall salmon decline in the Columbia River System:

Implication is that increases in ocean catch are directly responsible for decreases of in-river catches also shown.

During class (1998) a student made a fairly perceptive comment on the Ocean catch figure. She pointed out that the increase could be due to an increase in efficiency of catching salmon instead of just more boats on the water catching salmon. This has important implications:

This is the raw salmon count data at Boneville Dam that we will inspect more closely below. Evidence of quasi-cylical behavior is apparent.

Some relevant WWW resources for the above:

  • The Great Salmon Hoax
  • Comprehensive data source on Northwest Fish
  • Pacific Interdecadal Climate Change
  • HydroPower and the Columbia River System
  • Don't forget about Canada


    White Men Luv Fish


    Pacific Northwest Index


    Canadian Harvest Increases

    Some Salmon Links

    The above documents and data strongly suggest that a significant reason for Columbia river salmon decline is due to increased harvests in Alaska and Canada.

    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.

    So, be careful what you are told without being allowed to see the larger picture:


    World Salmon Harvest

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