ABSTRACT
Natural selection occurs when there are extreme fluctuations in the environment, indicating that variability and change are common to all living things. As world fisheries developed from the 1950s to the 1970s, there was an urgent need to determine how much fish could be harvested. High priority was given to research that would lead to the development of methods to identify levels of catch that were sustainable and hopefully stabilize the developing industries and economies of maritime communities. Changes that could occur in fresh water as a consequence of climate change would also have a major impact on Pacific salmon: migrations, spawning, hatching, and early rearing phases of the life history of salmon would be affected. Physical changes in temperature, precipitation, groundwater discharge, and increased ice-free periods for lakes could affect community structure and the survival, growth, and distribution of salmon species.
