Coho salmon used to run wild in the Santa Cruz Mountains of California. But those populations of coho were listed as endangered in the 1990s, and by 2008 the wild runs had declined to critically low numbers. Today, the remnants of those populations are hanging on with the help of a fish hatchery run by the non-profit Monterey Bay Salmon and Trout Project in collaboration with scientists from the NOAA’s Southwest Fisheries Science Center and the California Department of Fish and Wildlife.
Brian Spence and Joe Kiernan, both fisheries biologists and ecologists with NOAA Fisheries, are two of the scientists working with the hatchery. Together with other biologists, their goal is to increase the chances that coho salmon will run wild in the Santa Cruz Mountains again, and to do that, they’re doing more than just hatching fish and releasing them.
In order to maximize their growth and survival, young salmon need to hit the ocean when conditions are just right. In coastal California , that would be when seasonal upwelling brings cold, nutrient-rich water to the surface. However, that window of opportunity can be brief and can vary in timing from year to year. If the coho miss it because of bad timing, fewer of them will survive.
In Canada and Alaska—the heart of coho country—the young fish migrate out to sea over a short span of time, usually about a month. But in California, which is the southern end of their natural range, coho salmon migrate over a longer period of time, typically two-to-three months. Spence and Kiernan believe that by migrating out over a longer period of time, wild coho in California are hedging their bets against unpredictable ocean conditions. Even though many fish may miss the most favorable ocean window in a given year, at least some of them will be sure to make it when conditions are optimal.