Redwood Creek Coho Salmon Rescue and Captive Rearing Project

(Update) January 2019

  • On December 18, 2018, 165 adult Coho Salmon were released back into Redwood Creek. This marked the final year of a multi-year captive rearing program which began as an emergency rescue initiated during the summer of 2014. The primary goal of the program was to prevent local extirpation of Coho Salmon from the Redwood Creek basin. The National Park Service will continue monitoring salmonids in Redwood Creek this summer. In addition to a summary of distribution of spawning success per release location, scientists will collect tissue samples for parentage analysis. Combined with juvenile monitoring, an estimate of wild, hatchery reared, and summer population composition of Coho Salmon rearing during the summer of 2019 will be produced.
    • Total Released: 165
    • Females: 87 BY15 (3-year-olds)
    • Males: 76 BY15 (3-year-olds)
    • Immature Unknown: 2 BY15 (3-year-olds)
    • Average Fork Length: 481mm, Average Weight:1588g

(Update) January 2018

  • On January 12, 2018, 188 adult Coho Salmon were released back into Redwood Creek.
    • Total Released: 188
    • Females: 89 BY14 (3-year-olds)
    • Males: 87 BY14 (3-year-olds)
    • Males: 12 BY15 (2-year-old 'jacks')
  • During the summer of 2017, approximately 180 tissue samples were collected from juvenile Coho Salmon rearing in Redwood Creek. These will be analyzed to determine parentage (offspring or 'progeny' of released adults or naturally spawning origin).
  • In the summer of 2018, tissue samples will be collected from rearing juveniles for the same purpose as above.
  • The last cohort of approximately 200 adult Coho Salmon (BY2015 collected as juveniles in 2016) will be released in the winter of 2018/19, followed by juvenile sampling in the summer of 2019 for the same purpose as above.

(Update) December 2016

2016 Juvenile Collections

  • BY14 collected in 2015: 200
  • BY15 collected in 2016: 202

Juvenile Coho Salmon collected from Redwood Creek
Juvenile Coho Salmon collected from Redwood Creek (CDFW photo).

2016 Adult Releases

  • Total: 106
  • Females:69 BY12 (56 mature, 13 immature)
  • Males: 34 BY12 (32 mature, 2 immature)
  • Males: 3 BY14 jacks

Adult Coho Salmon preparing for release into Redwood Creek
Adult Coho Salmon preparing for release into Redwood Creek (CDFW photo).

netting fish from truck
Figure 1: CDFW and ACOE staff net Coho Salmon from the hatchery tank (CDFW photo).

On December 9, 2016, CDFW transported adult Coho Salmon from Warm Springs Hatchery to Redwood Creek, Marin County (Figure 1). A total of 106 hatchery reared, natural origin adult Coho Salmon were released into their natal creek to spawn. This marked the completion of captive rearing of the first cohort or broodyear (BY12) of Coho Salmon collected from Redwood Creek in 2014 (see full story below). The remaining two cohorts, that were collected in the summer of 2015 and 2016 are currently being reared at Warm Springs Hatchery, Lake Sonoma.

The timing of the release was near perfect with water rising and more rain in the immediate forecast (Figure 2). All released Coho Salmon were of Redwood Creek origin. With the exception of three BY14 jacks (2-year olds), all released fish were presumably BY12 (4-year olds).

2016/2017 Monitoring

Coho Salmon previously tagged with Passive Integrated Transponders (PIT) were scanned with a hand-held reader prior to release and the number and release site recorded (Figure 3). PIT tags are used to monitor spawning distribution. Colored floy tags are also used for easy identification of live fish.. The National Parks Service and Point Reyes National Seashore Association will conduct spawner and redd surveys this winter, and juvenile monitoing is planned for the summer to estimate spawning success.

Agency and locals gathered to watch the release of the adult Coho Salmon raised in captivity
Figure 2: Agency folks and friends gather to watch Coho Salmon released to their natal creek to spawn (CDFW photo)

Each Coho Salmon was PIT tagged prior to release
Figure 3: Biologists used a hand-held PIT reader to identify previously tagged Coho Salmon prior to release (CDFW photo).


(Update) October 2015

Juvenile Collections

  • 2014 Brood Year 2012 (BY12): 129 collected, 115 remaining
  • 2015 (BY14): 200 collected, 193 remaining
  • 2016 (BY15): 200 (planned)

Planned Adult Releases

  • Winter 2015: 3 mature males (BY12)
  • Winter 2016: 112 mature coho (BY12)
  • Winter 2017: 193 mature coho (BY14)
  • Winter 2018: 200 mature coho (BY15) (not yet collected)

All incoming juvenile coho salmon were placed in quarantine at Warm Springs Hatchery (WSH), also known as Don Clausen Fish Hatchery (DCFH) on Lake Sonoma, and treated with oxytetracycline and formalin to prevent bacterial and fungal infections.  Fish food consists of a combination of fry feed and natural krill.  An inventory of BY12 conducted in late September 2015 showed that most coho salmon in this group measured 290 mm (almost 12 inches) mean length and a mean weight of 380 g (over ¾ lb.).  A few fish in this group were significantly smaller.  Ultrasound (Figure 1) was the method used to determine if fish were mature, and examination revealed that only three of these coho salmon had visible gonads (all males). As an example, figure 2 shows the ultrasound image of a mature female from the Warm Springs 2007 broodstock.

Figure 1: Program lead, Ben White (ACOE) examines adult coho salmon using ultrasound.
Figure 1: Program lead, Ben White (ACOE) examines adult coho salmon using ultrasound (CDFW photo).

Figure 2: Example of female coho salmon ultrasound showing hydrated eggs.
Figure 2: January 2011 ultrasound image of female coho salmon (BY 2007) showing hydrated eggs (CDFW photo).


Facts and Highlights

Necessity of Project (2014)

The prolonged severe drought and past poor ocean rearing conditions in California are placing many endangered Coho Salmon populations at increased risk of extinction throughout the central coast. Recent annual adult Coho Salmon abundance in Redwood Creek is below 10 individuals in two brood-years and below 50 in the third brood-year. Juvenile coho abundance in 2014 is estimated below 200. Without captive rearing, there is a high risk that Redwood Creek Coho Salmon will completely disappear in the very near future.

Project Goal

To prevent extirpation of the three brood-years of Coho Salmon in Redwood Creek, temporarily increase spawner abundance, and preserve the remaining genotypes of the population.

Planned Coho Collections

Up to 300 juveniles in summer 2014, 2015, 2016. Initial collection date: Aug. 13, 2014.

Rearing Facility

Warm Springs Hatchery, also known as Don Clausen Fish Hatchery at Lake Sonoma in Geyserville..

Proposed Strategy

Genetically analyze captured fish and rear in freshwater for up to three years.

Planned Coho Releases

Release as mature adults in winter of 2016, 2017, 2018.

Initial Duration and Size of Project

Five years and up to 300 fish authorized (capture, rearing and release of three consecutive brood-years plus monitoring, 2014-2019).

Collaborating Agencies

California Department of Fish and Wildlife (CDFW), NOAA National Marine Fisheries Service (NMFS), Army Corps of Engineers (ACOE), California Department of Parks and Recreation (CDPR), Golden Gate National Recreation Area - National Parks Service (GGNRA-NPS).

Project Permitting

NMFS’ Section10(a)1(A) permits issued to the Russian River Coho Salmon Captive Broodstock Program; NPS and CDPR research and collecting permit; Interagency Fish Rescue Policy (CDFW/NMFS/USFWS). Fish rescue by CDFW is exempt under CEQA.

Questions and Answers

1. What is the status of coho salmon and their recovery in California?

Central California Coast coho salmon are listed as an endangered species under both the state and federal Endangered Species Acts (ESA and CESA), and the conservation of endangered species is an explicit State policy under the California Endangered Species Act (CESA). The causes of coho salmon decline in California are multiple and include loss of suitable habitat and climatic factors, such as poor oceanic conditions that reduce food availability and drought conditions that reduce the quality of stream rearing. Human activities contributing to the decline of coho salmon in California include the commercial overfishing of ocean stocks and the loss and degradation of suitable freshwater and estuarine habitats through land and water developments associated with agriculture, forestry, gravel mining, urbanization, water withdrawal and altered flow conditions, and river regulation. In the early 1990’s, declining coho salmon populations prompted the closure of all commercial and recreational fisheries for coho salmon in the State, followed by the listing of California coho salmon under CESA and ESA. Despite the legal protection, coho salmon populations in many coastal watersheds are still declining and some, particularly in the central coast, are already extirpated or approaching extirpation. There is considerable risk that populations of coho salmon, and other native salmonids present in many of California’s coastal watersheds, may become extinct in the wild within this century.

2. Why do California Department of Fish and Wildlife /NMFS propose captive rearing of Redwood Creek coho salmon?

Both the state and federal governments have prepared coho salmon recovery plans. These plans contain numerous recommendations which, if implemented, will help in the recovery of coho salmon. The prolonged severe drought in California is placing this coho population at increased risk of extirpation in the next few years, due to decreased freshwater survival and already extremely low abundance.

Coho salmon recovery actions fall into two broad categories: habitat-based actions and population-based actions. The protection and restoration of coho salmon habitat is an essential component of coho salmon recovery and it is unlikely that lasting recovery can be achieved without adequate amounts of functional habitat. However, habitat restoration alone will not achieve recovery if there are too few coho salmon left to maintain self-sustaining populations in the available habitat.

Populations that have been reduced in abundance to levels too low to maintain themselves through natural reproduction are candidates for captive rearing intervention. In the case of Redwood Creek (Marin County), population monitoring shows that annual abundance of adult coho salmon has fallen to single digits in recent years. The population is nearly extirpated, and captive rearing is proposed to prevent extirpation. This project would include temporary removal of juvenile coho from Redwood Creek, rearing them to maturity, and releasing them as adults back into their stream of origin. No hatchery spawning will occur. This project is a temporary measure that will help promote natural reproduction so that the population may persist in the future. The NOAA recovery target for this population based on historic carrying capacity is 272 adults per broodyear.

3. Why is captive rearing of Redwood Creek coho salmon proposed now and not earlier or later?

Captive rearing programs are a “last resort” effort to prevent local extirpation, or even complete extinction of a species within a region. In all captive rearing programs, the decision to intervene in population recovery through hatchery-based captive rearing must be weighed against the potential ecological and genetic risks of such interventions as well as the potential costs and demands on staff time and other agency resources. The decline in abundance of Redwood Creek coho salmon over the past decade, significantly exacerbated by the coast-wide crash in central California salmonid populations in 2008, as well as the current prolonged severe drought conditions in California greatly increases the possibility of a complete disappearance of coho salmon from Redwood Creek. Resource agencies have been monitoring coho salmon and implementing habitat restoration projects with the goal to recover this and other coho salmon populations in California.

Captive rearing of Redwood Creek coho salmon was first considered, and then recommended, as a coho salmon recovery action by the collaborative CDFW / NOAA Priority Action Coho Team (PACT) in 2012. The proposed captive rearing of Redwood Creek coho salmon has now reached a point of urgency, necessitated especially by the continuing drought conditions that have affected coho escapement in Redwood Creek this season and are likely to affect instream survival of any coho that were spawned last winter.

Given the current environmental conditions and the extremely low abundance of Redwood Creek coho salmon, any further delays in commencing captive rearing of Redwood Creek coho are likely to put the population at expected risk of extirpation.

4. What type of captive rearing is proposed?

Captive rearing strategies range from temporary rescue rearing of small numbers of salmon to full-scale conservation hatchery programs using artificial spawning. The proposed Redwood Creek coho salmon captive rearing project was developed as an appropriate approach balancing costs with the size of the watershed and program and the planned duration of the intervention. It benefits from the proximity of Don Clausen / Warm Springs Hatchery (WSH) and the experience and technical expertise developed in the Russian River Coho Salmon Captive Broodstock Program (RRCSCBP).

This Redwood Creek captive rearing project will commence in August, 2014. As currently proposed, it consists of collecting up to 200 juvenile coho from Redwood Creek in each of three consecutive years (2014-2016), rearing them at WSH to adulthood and releasing the mature adult coho back into Redwood Creek (2016-2018). A small number of adults from nearby watersheds (e.g., Olema Creek) that are also being reared at Warm Springs Hatchery may be released along with Redwood Creek coho to diversify the genetic makeup of the population, simulating natural straying that occurs in the wild and reducing potential inbreeding. This approach has three important advantages. First, it reduces the costs of maintaining consecutive generations of spawned fish at a hatchery facility. Second, it avoids artificial mate selection at the hatchery, instead permitting the mature coho salmon to spawn and choose mates freely in their natural environment. And third, it reduces domestication potential by subjecting the offspring to natural selection pressures in the wild from the moment of their birth.

To evaluate the success of captive rearing of Redwood Creek coho salmon, juvenile coho surveys will be conducted in each summer following the release of adult coho (2017-2019), and tissue samples will be analyzed genetically to determine how many of the released coho spawned successfully. Genetic analysis will be performed by Dr. Carlos Garza at the NMFS Southwest Fisheries Science Center (SWFSC) in Santa Cruz. The project is a collaborative effort between CDFW, NMFS, GGNRA-NPS, ACOE, CDPR, Friends of Lake Sonoma, and Golden Gate National Parks Conservancy. It is funded in part by the Redwood Creek Watershed Collaborative, a partnership of the CDPR, GGNRA-NPS, and the Golden Gate National Parks Conservancy. The project will be adaptively managed throughout its duration by CDFW, NMFS and GGNRA-NPS. 

5. What is the likelihood of success?

Biologists of the collaborating agencies agree that this project as currently proposed has a good chance of a positive outcome with a low risk potential. Several factors will contribute to successfully preventing the loss of the three coho salmon brood-years in the next few years. First, the Redwood Creek watershed is mostly in public ownership by land managers that are vested in the protection and restoration of creeks and their fauna and flora, both currently and into the future. In addition, the proposed captive rearing project will benefit from the experience and expertise of the hatchery staff implementing the Russian River Coho Salmon Captive Broodstock Program and the NPS monitoring efforts already occurring in Redwood Creek. Furthermore, this captive rearing and release proposal complements extensive restoration actions in the Redwood Creek watershed. GGNRA- NPS has recently implemented several habitat restoration and management actions that have improved instream, riparian and floodplain juvenile coho salmon rearing habitat. These restoration actions are increasing the stream’s capacity to accommodate higher numbers of fish, and this capacity is only expected to increase as the restored habitat matures.

Biologists seining Redwood Creek for juvenile coho salmon, August 2014
Biologists seining Redwood Creek for juvenile Coho Salmon, August 2014 (CDFW photo).

Adult Male Coho Salmon in net
Adult Coho Salmon ready for release into Redwood Creek, 2018 (CDFW photo)

Map showing Redwood Creek, Marin County and 2014 rescue sites - click to enlarge
Redwood Creek flows through Muir Woods and enters the Pacific Ocean at Muir Beach (Click image to enlarge)