Smoltification
A few important points:
* The above anadromous behavior is common in the northern latitudes where the ocean environment is often more productive than stream environments. Anadromous salmonids take advantage of both environments while in their different life stages.
* Smoltification only facilitates the transition that young salmonids make between fresh and salt water, it doesn't cause the movement.
* To this day, steelhead and
salmon in the Great Lakes have retained this anadromous migratory behavior
of their ancestral populations, but use the lakes to mature. It is
theorized that upon reaching the Great Lakes, steelhead will reverse
their smoltification process to maintain themselves in freshwater, due
to the increased forage available to them which satisfy their increased
metabolic demands.
* This is a scale taken from a
Lake Huron rainbow trout measuring 18.6 in. It illustrates the differences
in stream and lake growth due to the increase in food items available to
it once it entered the lake. Notice the increase width of the bands
in the lake growth portion. This is due to the increase in
growth rate.
This illustration was taken from
the following source:
MacCrimmon, H. R. and B. L. Gots.
1972. Rainbow trout in the Great Lakes. Sport Fisheries Branch,
Ministry of Natural
Resources, Ontario. 66 pp.