Science Spotlight

CDFW staff with tanker truck used to transport smolts


The Salty Lady sportfishing boat hosted Richmond youth


Smolts being released into Richmond Harbor






Fall-run Chinook salmon smolt

Moments after the sun set on Richmond Harbor’s Brickyard Cove on June 19, CDFW and its partners released approximately 200,000 hatchery raised juvenile fall-run Chinook salmon (known as smolts) into the bay.

The release was part of a larger effort to truck approximately 19.7 million fall-run Chinook salmon to locations in the San Francisco Bay, San Pablo Bay and lower portions of the Sacramento-San Joaquin Delta. CDFW has two more smolt releases planned for the week of June 20. Since beginning the effort in mid-April, staff have completed three to six releases per week.

Sunday night’s release was a collaboration with the City of Richmond, Golden State Salmon Association and Richmond Police Athletic League. The team invited a group of young people from Richmond to watch the release from a 56-foot sportfishing boat called The Salty Lady, the use of which was donated for the event to offer youth a glimpse into fishery operations.

“These kids definitely got a unique opportunity and a front row seat to watch this release,” said Senior Environmental Scientist Jason Julienne, supervisor over CDFW’s North Central Region hatcheries. “I hope it gets them interested and excited for fish and fishing, with the hopes of catching one of these fish when they return as adults in a few years.”

The goal of the releases is to improve survival of the salmon smolts by helping them bypass 50 to100 miles of hazardous river conditions caused by three consecutive years of drought in the Central Valley. CDFW fisheries biologists tracked flows and water temperatures in the fish's usual migration corridors and recognized that survival would be a challenge without intervention.

“We want to help ensure some of these fish survive to contribute to commercial and recreations fisheries, as well as hatchery and natural area production in the coming years,” said Julienne.

The smolts, raised at CDFW’s Feather River Fish Hatchery in Oroville, were eight to 10 months old when released. At that age, the smolts are developmentally ready to handle the salinity of bay waters. The Brickyard Cove location in Richmond was chosen because of its favorable tides and proximity to deep waters.

“We try to use outgoing tidal movements and the cover of darkness to help get these fish oriented in the right direction toward the Pacific Ocean, and reduce predation,” said Julienne.

All fish from yesterday’s release were marked and implanted with coded wire tags so CDFW can track their returns and determine how they contribute to fisheries and production in coming years.

For more information read CDFW’s news release on the trucking operation.

At Iron Gate Hatchery in Hornbrook, the fall 2018 spawning operation has just concluded. Iron Gate spawns both Fall-Run Chinook Salmon and Coho Salmon from the Klamath River. For Chinook, the hatchery staff manually collect the eggs and mix it with the milt immediately after the fish come into the facility. CDFW environmental scientists also collect heads from adipose fin clipped salmon, in order to retrieve implanted tags in the snout. The retrieved tags tell the biologists which hatchery the fish is from, and when it was released. They also collect scales, which enable them to determine the age of the fish.

For Coho Salmon, the process is a little more involved. The Coho are measured and samples taken, but the samples are sent off to a National Oceanic and Atmospheric Administration (NOAA) laboratory in Santa Cruz for analysis. While the samples are processing, the fish are kept in individually-numbered holding tubes at the hatchery. They will be spawned after the tissue analysis determines which fish are the best genetic match.

CDFW Photos

For more information about Iron Gate Hatchery, please visit: www.wildlife.ca.gov/Fishing/Hatcheries/Iron-Gate.

Media Contact:
Kirsten Macintyre, CDFW Communications, (916) 322-8988

Close-up of adult spring-run Chinook salmon dorsal fin.


Adult spring-run Chinook salmon inform river restoration decisions by their habitat use and preferences.


Adult spring-run salmon are carefully selected for release based on their sexual maturity.


Spring-run Chinook salmon released into the San Joaquin River are outfitted with three tags including a colored T-bar tag for visual identification.

Fresno County may seem an unlikely setting for salmon restoration and research, but some of the California Department of Fish and Wildlife’s (CDFW) most ambitious work with salmon anywhere is taking place in the heart of the parched Central Valley.

Since September, CDFW fisheries biologists have been spawning spring-run Chinook Salmon broodstock in the shadow of Friant Dam on the San Joaquin River. This season, CDFW staffers spawned 100 mature females that ranged in age from 3 to 6 years old  producing about 290,000 eggs.

It’s all part of an unprecedented, multiagency effort to restore an extinct, spring-run Chinook Salmon run to the San Joaquin River that is happening alongside river restoration efforts to make the river more salmon-friendly for a fish listed as threatened under both the state and federal Endangered Species Act.

Historically, spring-run Chinook Salmon were the most abundant salmon species in the Central Valley. Today, there are so few fish broodstock used for spawning comes from eggs collected at CDFW’s Feather River Hatchery in northern California. Meanwhile, construction is underway on a spring-run Chinook Salmon hatchery at the base of Friant Dam to support future runs of San Joaquin River salmon. The hatchery is scheduled to be completed in 2019.

During spawning, each female is crossed with four males to maximize genetic diversity. Samples of ovarian fluid are collected and sent to the CDFW’s Fish Health Lab for virology and bacterial analyses. Any egg lots determined to be potentially infected with pathogens are excluded from CDFW’s captive rearing program.

In June and August, 179 captive-reared adult fish – 59 females and 120 males – were released into the San Joaquin River to monitor what parts of the river the salmon prefer for holding and natural spawning.

Prior to release, each fish was outfitted with three tracking devices – an electronic passive integrated transponder (PIT) tag for individual identification, a colored, T-bar tag for visual identification, and an acoustic transmitter so their movements in the river can be monitored and recorded. Their habitat use and preferences inform river restoration efforts.

Spring-run Chinook Salmon spawn in the fall from mid-August through early October. So far, biologists have found 37 constructed redds – or salmon nests – in the San Joaquin River indicating some of the released salmon found enough cool water in the heavily damned and diverted river system to survive the Central Valley’s furnace-like summer and are now actively spawning in the river.

CDFW Photos by Travis VanZant. Top Photo: Prior to their release into the San Joaquin River this past summer, adult spring-run Chinook salmon were outfitted with acoustic transmitters so their movements in the river can be monitored and recorded.

The latest issue of California Fish and Game, the California Department of Fish and Wildlife’s scientific journal, is now available online! Issue 103(4) features articles that add to the knowledge base for three marine species, all of which face potential threats from overharvesting, incidental take and loss of habitat: Thorny stingray, Chinook salmon and green abalone. 

The Thorny stingray (Urotrygon rogersi) (PDF) is common in the eastern Pacific, from the Gulf of California south to Ecuador, and is frequently a by-catch of commercial shrimp trawlers. Little is known about its life history and movements. It was thought to occupy relatively shallow depths ranging from two to 15 meters, with a maximum recorded depth of 30 meters. In their published research, Acevedo-Cervantes et al. report the discovery of specimens at a depth of 235 meters—an indicator that the Thorny stingray has the capacity to survive beneath the disturbance of commercial shrimping activity. According to the authors, this new information is “of vital relevance” for the management of the species.

Adams et al. examined the effects of El Niño on adult Chinook salmon as they migrate through the Gulf of the Farallones (PDF). Researchers found that the dressed weight of commercial landed Chinook was lower during El Niño compared to non-El Niño years, a reduction attributed to a disruption in the normal feeding cycle in the Gulf of the Farallones. The analysis suggests that management agencies need to give more consideration to ocean conditions as risk factors in planning the recovery of endangered and at-risk Chinook salmon spawning runs.

Green abalone (Haliotis fulgens; Philippi) (PDF) were once part of a large recreational and commercial fishery, but are now estimated to be at less than 1% of their baseline density. Past attempts at restocking wild populations using juvenile farm-raised green abalone have resulted in high mortality rates. In “Outplanting large adult green abalone (Haliotis fulgens) as a strategy for population restoration,” author Caruso explores the efficacy of using adult specimens—at least 10 years old—to augment wild populations. The resulting 40 percent survival rate is much higher than the survival rates of previous projects that used juveniles. Although it is costly to raise green abalone to adult size, it may be the best method, given the decades of past unsuccessful restocking attempts.

These articles provide information useful to fisheries managers and should be helpful for future recovery efforts.

Cover photo © Peter Hemming

Habitat is the key to the long-term survival of Sacramento River winter-run Chinook in California. Since 1999, CDFW has been working with multiple agencies and private parties on planning efforts to restore the population of these endangered salmon. More than $100 million has been allocated to specific habitat restoration work on Battle Creek, which comprises approximately 48 miles of prime salmon and steelhead habitat.

Over the next two months, approximately 200,000 juvenile winter-run Chinook will be released into the North Fork of Battle Creek. The introduction of these fish, which were spawned from adults last summer, is occurring sooner than expected due the availability of fish from the Livingston Stone National Fish Hatchery Winter-run Chinook Captive Broodstock Program. The fish were raised at Coleman National Fish Hatchery and are being released by Coleman Hatchery personnel. These additional fish could help bolster the winter-run Chinook population and be a potential catalyst in their recovery.

CDFW Senior Environmental Scientist Doug Killam has worked on the Battle Creek Reintroduction Plan for nearly a decade and has been instrumental in moving in-stream projects forward. Killam sees the release of 200,000 smolts as an important step in the overall effort. The release will reestablish winter-run Chinook in a new drainage and create a separate new population. Currently there is only one viable population existing in the Sacramento River directly below Keswick and Shasta Dams. The recent drought affected the volume of the critical cold-water pool in Shasta Lake and the release of warmer water in the drought years of 2014 and 2015 resulted in major losses to eggs and young salmon below the dam. Biologists have long recognized that having more than one winter-run Chinook population is imperative for the long-term survival of the species.

A volcanic region with rugged canyons and dramatic scenery, the North Fork of Battle Creek is unique since it has both cold snowmelt water and large amounts of spring water flowing into it at critical times for winter-run salmon to hold over in and spawn in. It is also one of a handful of waters that can support all four of the Chinook salmon runs that return to the Sacramento River Basin. Hydroelectric development of the creek in the early 1900s largely eliminated winter-run Chinook and other salmonid runs from swimming far upstream to access the cooler water required for these unique summer spawning salmon. Recent efforts to bring the fish back to the North Fork include dam removals, rock fall removal, new fish ladders and fish screens and – most importantly – an agreement to increase stream flows to provide fish with the water quantity and quality they need to survive and thrive in this important keystone stream.

CDFW photo by Heather McIntire. Map by CDFW Fisheries Branch.