Originally Posted by
Steve Carson
This issue comes up every year when we do this stocking, so I'm going to try to do the short version.
The fish stocked in Irvine are a hybrid hatchery strain, since true "wild" steelhead take very sophisticated [expensive] facilities such as are maintained at the handful of DFG hatcheries that produce them for release in northern river systems.
The Irvine Lake fish start as a "true" steelhead crossed with a hatchery cutthroat, then backcrossed again to where the fish is roughly 75 to 80-percent steelhead.
Although not as efficient as hatchery-strain rainbows, these fish can be raised much more easily than what is required for the true "wild" strain.
FYI, all rainbows "can" become steelhead; but steelhead-strain fish have a kidney function that allows them to pass between freshwater and saltwater with only about 24 hours of acclimation time.
"Regular" rainbows would need 30 days or more of gradual acclimation in a brackish estuary to head out into saltwater.
There are numerous populations of "landlocked" steelhead that will never see salt water, both in California and other areas, most notably the Great Lakes.