Mokelumne River Hatchery

The fish trail below Camanche Dam

McIntire Road ends at a parking lot at the base of Camanche Dam, about 2 miles east of Clements. From the lot a self-guided route the California Department of Fish and Wildlife calls the fish trail passes the Mokelumne River, the fish ladder, the hatchery building, and the raceways. At the raceways, fish food is set out for visitors to throw to the salmon and steelhead. Picnic tables and restrooms stand in the riparian strip along the river. Two News-Sentinel men put kayaks in here at 6:30 one morning in 2007, a few feet from the fish ladder. The water churning out of the dam tumbled over yellow stones in the shallow riverbed, and the air, the reporter wrote, was “scented with oak.”

The hatchery draws its water from Camanche Reservoir and discharges it into the river. The dam marks the upper limit of anadromous fish migration on the Mokelumne. According to a state fisheries bulletin of 1929, fall-run Chinook is the only salmon run known to occur naturally in the river. The fish spend two to five years maturing in the Pacific and come back to these waters to spawn and die. Chinook spawning can be seen from mid-October to late December, and steelhead spawning from December to March. During those months visitors watch the artificial spawning through a viewing window. The department asks that they call ahead to be sure it is a spawning day.

The work at the window is done by department crews. In the 2017 season Brian Rodman worked the egg take, Kevin Fujimoto worked the spawning, and Joshua Deanfipps measured returned salmon. Another season found Sarah Sanders, a scientific aid, cutting coded wire tags from salmon heads. A 2019 News-Sentinel caption shows Jessica Wolff taking scale samples from returned Chinook. The hatchery’s annual production goal is 6,400,000 fall-run smolts. The East Bay Municipal Utility District of Oakland pays for the operation, and the state runs it. Schools, clubs, and scouts can book formal tours. Everyone else walks the trail alone.

The river takes its name from the Miwok, and the name is said to mean “people of the fishnet.”

A spawning channel in place of a hatchery

Before Camanche Dam, salmon and steelhead ran up from the Delta as far as Pardee Dam. Frederick H. Groh wrote the installation’s first annual report for the Department of Fish and Game. In it he dates the dam’s completion to 1963 and puts the spawning ground lost behind it at about 12 miles. The district’s own milestone list gives 1964 for the dam. The district built the fish facility to compensate for the loss. The state’s history page says it was built in 1963. Other accounts, including the CalFish hatchery page and the Lodi News-Sentinel, give 1964. Groh records that the installation, then called the Mokelumne River Fish Installation, first operated January 1, 1964.

The design came from a trial. In the fall of 1960 the district and the department built an experimental salmon spawning channel upstream of the present site. It worked well enough that the district built a permanent spawning channel instead of a standard salmon hatchery. A hatchery with six concrete rearing ponds was added for steelhead. The channel ran in two loops with resting pools spaced 500 feet apart. A later state report gives its length as 6,800 feet and its bottom width as 20 feet. Salmon climbed the ladder to a sorting tank, where a mechanical sweep and lift dropped them into an anesthetic tank for counting before release into the gravel. Groh called it “among the largest artificial spawning channels in the world.”

The first season was a short one. The reservoir held too little water for the planned 60 cubic feet per second, and on October 9, 1964, the channel opened at 38. The first king salmon came up the ladder on October 17 and the last on December 5. The run counted 184 males and 178 females, 362 fish in all. Of these, 120 were hauled by tank truck from the Woodbridge counting station between November 24 and 28. Eggs lay in the gravel about 50 days before hatching. A trap at the outlet caught 73,540 fry heading downstream. Groh doubted the figure. Algae had forced crews to bypass part of the flow, and 5,100 yearling steelhead had slipped into the channel with the adult salmon. When crews cut the steelhead open, almost every stomach held salmon fry. Groh promised a fish rack for the next year. A 300-foot observation area was fenced along one channel, and 25,220 people visited between January 1964 and June 1965.

Zinc, drought, and new raceways

In the seasons that followed, gravel berms a foot high and 150 feet apart were built across the channel, first for the 1968-69 season, to keep spawning females from digging over one another’s redds. Philo F. Jewett’s report for 1972-73 counts an estimated 16,000 visitors that year. The same season brought only 353 salmon, too few to use more than one loop. That January and February, for the first time since 1967, copper and zinc in the water killed 40,800 steelhead fry and 5,400 yearlings. “We now have no way to control the concentrations of these metals in our pond water,” Jewett wrote, “but we do monitor them.”

From 1987 to 1992 drought hit the river. The state history notes that low flows and a series of fish kills had already reduced the Mokelumne steelhead run during the 1980s. The district responded with programs for water quality, flows, and habitat. Since the late 1990s some 70,000 cubic yards of gravel, about 300 dump-truck loads, have been added each year to the river near the hatchery to widen spawning room.

By 2000 the department office had long been outgrown by manager Rich Bryant and his staff. A plan first drawn in 1996 was trimmed to $12.5 million. It called for a 6,000-square-foot office, a freezer building for salmon feed, sixty 100-foot raceways, and a 150,000-square-foot bird exclosure. “We pay the bills,” said district spokesman Charles Hardy. Bryant explained the cuts: “We had to choose between the fish and us, so we cut storage space that the original plan included.” Construction went on while the hatchery kept raising about 3 million salmon smolts, though no yearling steelhead were raised in 2001. A dedication was held at the hatchery on October 4, 2002. The Commercial Salmon Stamp Fund paid for another building that year.

Counting the runs

In 2008 the Central Valley salmon stock collapsed, and very few fish came back to the valley. The district’s fisheries manager called it an eye-opener. Managers began timing pulse flows to cue the fish to move. The hatchery had already stopped trucking young fish to the river and dumping them through a pipe. Instead it held them an hour or two in a net pen to acclimate. In 2011 the hatchery recorded a return of 18,000 salmon. In 2017 more than 19,650 came back. The district reported record runs again in 2023 and 2024 and credited them in part to the closure of ocean commercial and recreational fishing.

The river supplies only about 3 percent of the fresh water entering the Delta. The district says its salmon have made up as much as 50 percent of the commercial catch off the California coast. More than 10,500 Chinook returned in the 2025 fall run, and the hatchery collected and fertilized its goal of 7.5 million eggs. Over 730 steelhead came into the hatchery that year. “We had limited water available for pulse flows to attract migrating fish due to the drier year,” said Michelle Workman, the district’s manager of natural resources, “but our management strategies and hatchery investments to support Chinook on the Mokelumne have proven to be resilient.”