Biology 2483A Lecture : Ecology Notes
23 Nov 2012
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Document Summary
Potential causes of salmon declines in the north pacific ocean dam construction (interfere with salmon migrating), sediment from logging operations, water pollution, and overharvesting. But the conditions of oceans, where salmon spend most of their time as adults, have also been implicated (the problem has more to do with oceans than streams). Hare and francis (1994) studied fish harvest records and showed alternating periods of high and low production associated with climatic variation in the north pacific. There is a lot of variability in salmon harvests from year to year, with abrupt increases and decreases in production. Mantua et al. (1997) found that periods of high salmon production in alaska corresponded with period of low production in oregon and washington. They also found a correlation between salmon production shifts and sea surface temperatures. Spatial context is important not all pacific salmon were decreasing in numbers. The physical environment ultimately determines where organisms can live and the resources that are available.
