In a recent post I brought up the subject of using the right breed of Spring Run Chinook for restoring San Joaquin salmon.1 Breeding (genetics) is important when introducing hatchery fish to a natural system. For salmon, the idea is to match the native fish as closely as possible, because the native fish have adapted to the specific river conditions. Researchers have found that salmon in a river system go back to where they were born because of that adaptation. In Alaska, biologists found that salmon were adapted to specific small tributaries on larger rivers, and identified all sorts of locally adapted traits.
Decades ago, the native Lahontan cutthroat in the Pyramid Lake-Truckee River-Lake Tahoe watershed were wiped out and subsequently replaced by another nearby stock. But these fish did not grow to the large size of the native fish. Then, two decades ago the US Fish and Wildlife Service found some of the original native stock that had been transplanted to Colorado. So US Fish and Wildlife brought the native stock back, and the Paiute Hatchery now uses them. They are now naturally reproducing in the Truckee River immediately upstream from Pyramid Lake.2