Photo: Summer Burdick, USGS

Recent reports from the Klamath River reveal a troubling challenge facing juvenile salmon. Scientists have found that many young Chinook salmon are becoming infected with a microscopic parasite called Ceratonova shasta, a disease that attacks the digestive tract and can be fatal to young fish before they ever reach the ocean.

While the Klamath River and the San Joaquin River are very different systems, the situation offers important lessons for those working to restore native fish populations here in California’s Central Valley.

One of the most important lessons is that fish recovery is about much more than simply getting water from one place to another. Salmon must survive a complex journey through rivers where water temperature, flow, habitat quality, predators, and disease all interact.

Researchers have found that Ceratonova shasta thrives under conditions that include warmer water temperatures, slower river flows, and longer periods of exposure for young salmon. These are challenges that are not unique to the Klamath. These are also conditions that can occur in portions of the San Joaquin River downstream from Highway 99 and the Fresno Aquarium property, particularly during the warmer months of the year.

As juvenile salmon move through the San Joaquin River Restoration Program reaches, they face many of the same obstacles that salmon encounter throughout California. Warm water can increase stress. Low flows can reduce available habitat. Slower-moving water can lengthen migration times. Predators may have more opportunities to feed on young fish. Disease organisms can take advantage of fish that are already stressed by environmental conditions.

The Klamath experience reminds us that successful salmon restoration requires attention to the entire ecosystem.

That means protecting cold-water sources whenever possible. It means restoring floodplains and side channels that provide healthy habitat. It means maintaining river conditions that help juvenile fish move efficiently downstream. And it means continually monitoring fish health so that emerging disease problems can be identified before they become widespread.

For the Fresno Aquarium, this is one reason our future native fish exhibits will focus not only on the fish themselves, but also on the river processes that support them. Visitors will learn how water temperature, seasonal flows, floodplains, habitat complexity, and water quality all work together to determine whether salmon survive.

The lesson from the Klamath is not one of failure. Rather, it is a reminder that river restoration is a long-term effort that requires patience, science, and adaptive management. As California continues working to restore salmon runs in both the Klamath and San Joaquin watersheds, every challenge teaches us something new about what these remarkable fish need to thrive.

The San Joaquin River and the Klamath River may be separated by hundreds of miles, but the lessons learned in one watershed can help guide conservation efforts in the other. By studying these challenges carefully, we can continue working toward a future where healthy rivers support families, farms, and fish alike.