“This is the bible,” she said of the matrix. “It’s what Carlos says.”

John Carlos Garza, a geneticist based a day’s drive south in Santa Cruz, has become a key figure in California’s effort to preserve its decimated salmon stocks. Using the latest genetic techniques, he and his team decide which individual fish should be bred together. At several major state conservation hatcheries, like the coho program here at Iron Gate, no two salmon are spawned until after Dr. Garza gives counsel — a “salmon mating service,” he jokingly calls it.