Aquatic Biome Regents Questions
Decline of the Salmon Population
Salmon are fish that hatch in a river and swim to the ocean where
their body mass increases. When mature, they return to the river where
they were hatched and swim up stream to reproduce and die. When
there are large populations of salmon, the return of nutrients to the
river ecosystem can be huge. It is estimated that during salmon runs in
the Pacific Northwest in the 1800s, 500 million pounds of salmon
returned to reproduce and die each year. Research estimates that in
the Columbia River alone, salmon contributed hundreds of thousands
of pounds of nitrogen and phosphorus compounds to the local ecosys-
tem each year. Over the past 100 years, commercial ocean fishing has
removed up to two-thirds of the salmon before they reach the river
each year.
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