One of the interesting aspects pop steelhead bilology is that both hatchery and wild fish seem to return based on smolt age. The age-1 smolts return earlier than age-2 which return earlier than age-3. This appears even in the F1 generation of wild fish taken into the hatchery and released as 1s.

Because WDG needed to get fish to size in one year they further selected the earliest maturing fish. This also pushed return times earlier.

Want more early-returning hatchery fish? Significantly increase in stream productivity. Most easily accomplished by increasing salmon escapement but has also worked in the outfall stream from a sewage treatment plant in Idaho.