Science Spotlight

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  • February 1, 2019

Concrete fish ladder along hillside and river. Hills in background.

Blue sign with red spray-painted text reading 'house spawning'

Fish splashing in water between gate and metal examination chute.

Two people in yellow rain jackets in hatchery facility alongside fish chute filled with fish.

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

Categories: General
  • October 26, 2018

Several people wearing waders in streambed holding nets in water
CDFW staff and volunteers set a one-day record of 1.5 million eggs collected on the Little Truckee River earlier this month.

People holding white net in water with several kokanee salmon in net
CDFW staff and volunteers use seine nets and electric fishing techniques to corral and capture adult Kokanee salmon.

Several people wearing waders holding nets in streambed. Boat and trees in background.
Volunteers from the California Inland Fisheries Foundation, Inc. and Kokanee Power help CDFW personnel capture Kokanee salmon.

Each October, conditions permitting, CDFW staff and volunteers from the California Inland Fisheries Foundation, Inc. and Kokanee Power descend on the Little Truckee River, just upstream from Stampede Reservoir near Truckee, and get to work on the annual Kokanee Egg Take.

Using seine nets and electrofishing techniques to corral and capture adult Kokanee Salmon, staff and volunteers then collect eggs and milt (fish semen) add them together in specific ratios to complete the spawning process. The fertilized eggs are carried to an egg care station on the side of river where they are measured, enumerated, disinfected and finally placed in containers to be transferred to the San Joaquin Hatchery.

Staff at San Joaquin Hatchery incubate, hatch and care for the early-life stages of the resulting baby salmon. Some fertilized eggs are shipped to other CFDW hatcheries for hatching and rearing. Resulting fingerling fish are stocked to several approved waters in the state to provide recreational angling opportunities.

“By all accounts, this year set the one-day egg take record of 1.5 million eggs,” said Roger Bloom, CDFW’s Inland Fisheries Program Manager. “This was a collective effort from our scientists, hatchery staff and stakeholders that culminated into actions in support of fisheries across the state. Given the magnitude of eggs taken on that record day, it took a non-stop effort of over 23 straight hours to get the job done, which highlights the dedication and resolve CDFW personnel have -- especially the hatchery staff who now will care for these eggs that will eventually grow to be little salmon!”

Kokanee Salmon were introduced into California waters to provide diverse recreational angling opportunities for anglers and have become an extremely popular sport fish. They are typically smaller than the landlocked Chinook Salmon, with an average size of about 12 inches. This summer, CDFW will release the Kokanee Salmon fingerlings that emerge from this collection effort into lakes and reservoirs throughout the state.

The landlocked version of the Sockeye Salmon, the Kokanee (pronounced coke-a-nee) Salmon spends its entire life in fresh water. Instead of migrating to the ocean, adult Kokanee Salmon inhabit large lakes before returning to their natal streams or gravelly shorelines to spawn. Like all Pacific salmon, Kokanee die after spawning, the whole life cycle taking from two to four years.

CDFW Photos. Top Photo: Volunteer holds a Kokanee salmon during work on the Little Truckee River.

Categories: Wildlife Research
  • October 19, 2018

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

Close up shot of salmon with mouth open wide while held in hand
Adult spring-run Chinook salmon inform river restoration decisions by their habitat use and preferences.

Man wearing khaki colored waders, grey short sleeve shirt, orange vest and green CDFW baseball cap standing in water bent over holding salmon. Two other people standing in background.
Adult spring-run salmon are carefully selected for release based on their sexual maturity.

Salmon with blue tracking device held above white net over water
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.

Categories: Wildlife Research
  • April 5, 2018

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 link opens in new windowThorny 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 link opens in new windowEl 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.

link opens in new windowGreen 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

Categories: California Fish and Game Journal
  • March 23, 2018

A brownish-green river with a glassy surface flows through semi-arid land as two men fish from the rocky shore
Surveying Ventura River in Ventura County

A person in a black, full-body wetsuit floats, face-down, in a clear, shallow stream lined by forest and riparian vegetation
Snorkel survey in Hollow Tree Creek in Mendocino County

A young steelhead trout is barely visible, camouflaged against greenish-golden rocks in a stream
Hollow Tree Creek steelhead

Taking care of California’s fish and wildlife wouldn’t be possible without managing the resources upon which they depend. To that end, CDFW has an entire branch – and many scientific staff – dedicated to the scientific study, and planning and management of water resources.

Within the Water Branch, CDFW’s Instream Flow Program (IFP) is tasked with collecting and contributing data necessary to make all kinds of important management decisions about ecological function, fish rearing, spawning and migration and habitat suitability.

In the simplest terms, “instream flow” refers to the rate of the water running through a waterway in a natural environment. But when one considers all the interests competing for use of that water – fisherman, boaters, farmers, businesses, water districts, and fish and wildlife themselves – the complexity of the subject is evident.

Measured in cubic feet per second (cfs), instream flow can be measured at different times of the year in a specific location in a waterway. The fluctuations can tell scientists quite a bit about the ecosystem health of a watershed. While some watersheds have flowing water throughout the year and others are intermittent it is often the responsibility of water managers to distribute the water between uses. CDFW, a natural resource management agency, is faced with the complex task of identifying and recommending instream flows necessary for supporting natural resources. Determining instream flows are crucial so that aquatic, riparian, and terrestrial resources dependent on water will be considered and protected during water distribution activities.

Guided by the California Water Action Plan, the Public Resources Code and the Fish and Game Code, IFP staff conduct flow studies, collect field data, develop guidelines for quality assurance, conduct outreach and coordinate with other agencies and interested parties on program-related activities.

In the past year, some of IFP staff’s largest projects have included:

  • A flow study at the South Fork of the Eel Watershed, which supports threatened coho, Chinook and steelhead.
  • A study of 46 coastal steelhead streams (Ventura County to Siskiyou County) to develop flow criteria and evaluate historic flow trends.
  • A flow study to identify flow regimes that will protect endangered Southern California steelhead in the Ventura River.
  • Technical studies and final flow recommendations based upon the needs of South-Central Coast steelhead in Monterey County’s Big Sur River.
  • Ongoing training for IFP staff, to ensure that field studies in swift water are carried out safely.

To learn more about these specific projects, please download the link opens in new windowIFP’s 2017 Year in Review (PDF) document, available on CDFW’s website.

A Featured Scientist Q&A with the IFP manager Robert Holmes is also available on the CDFW Science Institute page.

CDFW photos. Top photo: IFP staff hold a planning meeting prior to a survey on the Ventura River in Ventura County

Categories: General