Survival to Adulthood of American River Hatchery Salmon

The Nimbus Fish Hatchery on the American River produces approximately 4 million fall-run Chinook salmon smolts each year for release to the American River and to San Pablo Bay (after being held there in net pens). Releases are made from late April to early June. Release return rates are available for 2007-2015.1 In 2014 and 2015, all releases were to the Bay. From 2016 to 2018, a substantial proportion of releases were to the American River.

Return rates (percent captured as adults in fisheries plus percent returning as adults to spawning grounds and the hatchery) from 2007 to 2015 releases varied from 0.3 to 3.7 percent (Figure 1). Return rates were higher for wet year 2011 and normal years 2010 and 2012. Return rates for river and Bay release groups were similar in wetter years. Overall return rates in dry years were lower than return rates in wetter years, with higher returns for Bay release groups than for river release groups.

River return rates were low in years with lower flow and higher water temperature in the lower American River. American River flow was lower in late spring 2009 and 2013 (Figure 2). River temperatures were higher (>55oF) in these drier years (Figure 3), as were Delta temperatures (>68oF; Figure 4). Such conditions are detrimental to smolt survival.

Poor returns (<1%) from dry year Bay releases (<1000 cfs Delta outflow) are associated with low Delta outflows (<10,000 cfs, Figure 5). Lower ocean survival may have also contributed to poorer Bay release returns.

Conclusions and Recommendations

An optimal strategy for increasing the contribution of Nimbus Hatchery’s 4 million fall-run Chinook salmon smolts would be:

  1. Release smolts in the American River in wetter years with higher river flow and lower river water temperature.
  2. Release smolts in the Bay in dry years; do not release in river.
  3. Maintain Delta outflows above 10,000 cfs during periods of release of smolts to the Bay.

This strategy could increase hatchery smolt returns as much as 1%, or by 40,000 adult salmon, assuming 4 million smolts. In drier years, this would double or triple the contribution from the American River hatchery to salmon available for catch and to salmon returning to the American River to spawn.

Figure 1. Return rates for Nimbus Hatchery smolt late spring releases to the American River (red dots) and San Pablo Bay (black color dots).

Figure 2. Lower American River flows 2009-2013. Red dots indicate periods of release of hatchery smolts to the river.

Figure 3. Water temperatures in the lower American River from 2009 to 2015. Red dots indicate periods of release of hatchery smolts to the river.

Figure 4. Water temperatures in the north Delta 2009 to 2015. Red dots indicate periods of release of hatchery smolts to the river.

Figure 5. Delta outflows 2007-2015. Red circles indicate periods of release of hatchery smolts to the Bay.

Response to Bay-Delta Science Paper on The Problems with Coleman Hatchery Salmon Straying

In a Maven 1/17/19 post, US Fish and Wildlife Service hatchery managers discuss problems that have developed from trucking salmon smolts from the Coleman National Fish Hatchery (Coleman NFH) to San Francisco Bay. Chief among these problems is that juvenile fish trucked from Coleman NFH stray into other Central Valley rivers as spawning adults, rather than returning to Coleman NFH. This has become a general argument for releasing Coleman NFH smolts near Redding instead of trucking or barging them to the Bay.

During the 2013-2015 drought, many Coleman NFH smolts were trucked to the Bay for release to meet the hatchery’s goals:

The management goals for the hatchery are to provide about 1% of their production or about 120,000 fish from each brood year to the ocean fishery, the freshwater sport fishery, and returns to Battle Creek for brood stock, all while trying to reduce negative impacts on naturally spawning fish.

From 2013-2015, 35.5 million fall run smolts, about 12 million per year, were reared for release by the Coleman NFH. In 2013, all were released at the hatchery into Battle Creek. In 2014, 3.4 million were released at the hatchery, and the remainder were trucked to the Bay. In 2015, all 12 million were trucked to the Bay. Since 2015, all Coleman NFH fall-run smolts have been released at the hatchery.

Trucking during the drought did meet the 1% production goal, but did not provide adequate hatchery returns for broodstock and did not achieve low straying rates.1 The USFWS has since chosen to ignore the production goal in order to achieve the other two goals. In dry years, the 12 million smolts now provide 10,000-20,000 adults (0.1-0.2%) to fisheries instead of 100,000-200,000 (1-2%). Instead of increasing hatchery production by barging smolts or improving post-release river conditions (higher flows), the fall-run salmon production program at Coleman NFH, designed explicitly as mitigation for loss of salmon from the federal Central Valley Project, is not meeting its primary mitigation goal.

In the response to Maven’s questions on USFWS presentation at the Bay-Delta Science Conference, the USFWS managers offered the following responses:

Is Straying Bad?

  • This occurs because fish that do not naturally emigrate through the river system lose the opportunity to imprint properly and may be unable to locate their natal area when they are ready to spawn. Response: High stray rates are unique to the federal Battle Creek Coleman NFH, partially because many of their returning adults spawn in the upper Sacramento River (as intended) and do not move into Battle Creek, and are thus considered strays. Regardless of imprinting influence, returning adults to the Sacramento River are confronted with poor flows and high water temperatures above the mouth of the Feather-Yuba-Butte Creek, Mokelumne, and American rivers, so they choose those rivers out of necessity. This problem does not occur at the Feather, American, and Mokelumne state hatcheries. These other hatcheries have also transported stray, earlier-returning Battle Creek adults (or fertilized eggs) to the Coleman Hatchery to help Coleman offset its egg shortages.
  • Hatchery fish that stray into natural spawning areas can detrimentally affect natural fish populations through genetic, ecological, and behavioral mechanisms…. Increased straying by hatchery fish may reduce genetic diversity within and among salmon populations. Response: While this is generally true for pristine natural salmon watersheds, this concern was long ago lost in the Central Valley after a century of disturbance and hatchery interference. Eggs have been shared, even from out of state, and even from different runs (hatcheries and dams have forced mixing of spring-run and fall-run spawners). Hatchery strays continue to dominate runs in non-hatchery rivers; without the strays, there would be few if any salmon in these rivers. Straying is also a natural process needed to retain population fitness, resilience, and genetic diversity.
  • Likely due to the prevalence of off-site release practices at Central Valley hatcheries, Central Valley fall Chinook Salmon have lost locally adapted genes and become one large, genetically homogeneous population (see Johnson et al 2012). Response: Adapted genes were lost decades ago before off-site releases. Johnson et al were describing how hatchery dominance covers up underlying problems in wild populations, not necessarily how it causes the underlying problems. This is a real concern in the Central Valley where only 25% of the fall run hatchery smolts are marked. The true wild components of individual river runs need protection. For some rivers, natural spawning areas can be reserved for true wild spawners (e.g., Battle Creek, Yuba River, Mokelumne, Calaveras, Butte Creek, etc.). Wild spawners can also be relocated above rim dams. Conservation hatcheries can use “wild” spawners.
  • Furthermore, salmon that are spawned and reared in fish hatcheries may become quickly adapted for characteristics that favor their survival and reproductive success in the hatchery environment while, at the same time, diminishing their ability to survive and reproduce in the natural environment. Response: while potentially (and historically) true, modern hatchery programs minimize or should minimize, if not reverse, these tendencies.
  • Stray hatchery fish may also compete with natural fish populations for limited resources, including competition for preferred spawning areas by adults and competition for food resources and habitat by juvenile fish. Response: Again, while generally and historically true, hatchery adult returns now take the place of wild adults in increasingly depressed amounts of spawning habitat in Central Valley rivers. Also, it is generally known that in many cases wild adults out-compete hatchery adults for habitat. Also, in most Central Valley rivers, hatchery fall-run adults can be effectively excluded from primary spawning areas. Hatchery smolts can readily be excluded from natural rearing areas by controlling timing and location of releases. In arguing against barging or trucking, USFWS managers are in essence arguing to continue releasing their hatchery smolts into prime natural rearing areas.
  • When hatchery fall Chinook Salmon from Coleman NFH stray at high rates, the freshwater fishery may be redistributed to other parts of the Central Valley and sport fishing in the upper Sacramento River fishery is negatively impacted. Response: Low flows and high water temperatures are the biggest contributor to poor upper Sacramento River salmon fishing.2 Also, Coleman hatchery adults that spawn in the upper Sacramento River or that are caught by sport fisherman in the Sacramento River upstream of Battle Creek are considered strays, even though they are produced to mitigate for Shasta Dam.
  • High stray rates of trucked hatchery fish may impact the ability of Coleman NFH to meet its annual fish production targets. For example, in 2017 (which corresponded to age-3 adult returns of fish that were 100% trucked), less than 350 adult salmon returned to the hatchery. At a minimum, Coleman NFH needs to spawn 2,600 pairs of adult salmon to meet the production target of 12 million juveniles. As a result, Coleman NFH released less than 6 million juveniles in the spring of 2018, which will result in fewer fish available to achieve our management goals in future years. Response: Then why not release a portion of the smolts in the Bay as for brood year 2013 (2014 releases)? Other potential measures to increase egg take outlined by the authors can also be enhanced.

Need for Trucking

  • California’s drought had some negative impacts for Coleman National Fish Hatchery….The one percent contribution goal to the fisheries and returns to Battle Creek was not able to be achieved under the drought conditions. Response: The drought was not to blame. Reclamation’s water right permits require measures to protect salmon, even during droughts. During the 2013-2015 drought, Reclamation delivered too much water to Sacramento River settlement contractors. This left Reclamation too little water to meet the conditions in its water rights permits that are designed to protect salmon. Water management during droughts is the problem.
  • Despite our extra efforts to collect additional eggs, we only met about half of our production target. We’ve undertaken a study to assess fish survival under different release strategies. This information will hopefully allow for adaptive management, based on changing environmental conditions and may give us some flexibility to release fish onsite to meet our multiple management goals in the future. Response: If Reclamation provides environmental flows from Shasta, and if USFWS times releases of hatchery juveniles at Coleman NFH to water conditions, then Battle Creek releases may produce more adult salmon. Some amount of trucking may be necessary to meet overall mitigation goals.


Hatchery program managers should not give up on trucking and on reducing high stray rates. They should consider barging juvenile salmon to better imprint smolts and improve smolt survival. Federal water managers also need to improve lower Sacramento River conditions for returning adults, in order to reduce straying. Water contractors and state/federal purveyors must also collectively limit their water diversions to meet water right permit conditions and water quality standards that are designed to protect fish. Egg taking should be increased if hatchery releases are to continue, in order to meet mitigation goals. These measures will all help hatchery managers meet their adult production goals and mitigation commitments. Trucking, a standard practice at state hatcheries in all year types, may be necessary, especially in periods of drought, to meet mitigation goals.

Washington State increasing hatchery salmon production Major realignment toward wild population recovery

Washington State is increasing salmon production to help in recovery of near extinct salmon populations and orca (killer whales). A Washington state Department of Fish and Wildlife webpage describes the role of hatcheries in restoring wild salmon stocks:

In recent years, state hatcheries also have taken on an equally important role in helping to recover and conserve the state’s naturally-spawning salmon populations. Nearly all the hatcheries in the Columbia River and a number of hatcheries in Puget Sound play a role in wild fish rebuilding programs, whether by rearing juveniles prior to release or holding fish through their lifespan to ensure the survival of depressed stocks. This renewed focus on wild stock recovery represents a major realignment in hatchery operations, as WDFW, the tribes, federal government and independent scientists worked to develop a comprehensive operations strategy for hatcheries in Washington. 1

The main reform actions being taken in Washington’s program are:

  1. Marking all hatchery salmon smolts allows identifying hatchery fish by hatchery and lot group. It also allows mark-selective fisheries that require release of wild salmon.
  2. Developing salmon population-specific recommendations intended to provide scientific guidance for managing each hatchery more effectively in the future.
  3. Keeping hatchery program budgets in pace with increasing operating costs (especially utilities, fish feed and labor costs), and not forcing cutbacks in some programs.
  4. Updating aging hatchery infrastructure.
  5. Supplementing wild stocks: to maximize egg fertilization and fry survival (of wild) and thereby increase the number of “wild-type” smolts heading out to the ocean.
  6. Maintaining captive broodstocks of endangered stocks with dangerously low population levels: juveniles are maintained in a hatchery for their entire life to ensure the stock’s survival.
  7. Minimizing interaction between naturally-produced and hatchery-produced outmigrating juveniles and adult fish returning to streams to spawn where necessary.
  8. Donating surplus adult salmon from hatcheries to non-profit hunger-relief programs.
  9. Introducing hatchery carcasses or analogs back to streams to increase natural productivity to low productivity streams.

While California is slowly moving toward some of these reforms, there is resistance to others. For more information and links on California hatchery programs see , , , .


Mokelumne River Salmon Update – Fall 2018

Dan Bacher’s report on 2018 salmon returns to the Mokelumne River Hatchery provides continuing good news for the Mokelumne River salmon run.

When I last reported on the fall run of Mokelumne River salmon, I described strong runs from 2010-2016. The 2017 run was exceptionally strong (Figures 1 and 2), despite being the product of the 2013-2015 drought. This success story is in large part due to the management of the Mokelumne River Hatchery, as reported in the Bacher article. Trucking hatchery smolts to the lower San Joaquin in the western Delta near Jersey Point greatly improves survival over releases of salmon in the lower Mokelumne River.

Best returns from the spring 2015 releases were from smolts barged and released near the Golden Gate. That group of 101,000 smolts (tag code #060593) had a good return of 1.35 percent compared to 0.06-0.80 % from smolts released in the west Delta and 0.01 % released in the lower Mokelumne River. In early May 2015, soon after river and Delta smolt releases, water temperatures reached 68oF in the west Delta and 72oF in the lower Mokelumne in the central Delta, levels stressful to smolt salmon. Delta outflow in early May 2015 was critically low at ~5000 cfs. Net flow in the lower San Joaquin River in the west Delta, with the Delta Cross Channel closed, was near zero.

The returns from tag group #060593 (shown in Figure 3), which represented only about 3% of the total smolts releases from the Mokelumne Hatchery in 2015, exemplifies the kind of return pattern that can be achieved by a progressive hatchery program. The majority of the adults returning from this tag group to the Central Valley were to the hatchery (192), although a significant number strayed to the neighboring American River (82) and San Joaquin River and its tributaries (40). In previous years, the California Department of Fish and Wildlife achieved similar success barging smolts from the Feather River Fish Hatchery.1

Figure 1. Mokelumne River in-river fall Chinook returns (escapement) 1975-2017.

Figure 2. Mokelumne River hatchery fall Chinook returns (escapement) 1975-2017

Figure 3. Mokelumne River fall Chinook tag returns through 2017 from 101,000 Mokelumne River Hatchery smolts, tag group #060593, barged to and released near the Golden Gate Bridge.

Sacramento River Salmon Science

A recent paper in the prestigious Canadian Journal of Fisheries and Aquatic Science discusses Central Valley salmon. The paper concludes: “Wild stocks in several California rivers are now dominated by hatchery fish (Barnett-Johnson et al. 2007; Johnson et al. 2012; Quiñones and Moyle 2014), potentially eroding the long-term resiliency of wild, locally adapted populations by disrupting selection for heritable traits that improve lifetime reproductive success in variable environments.”

First, wild or naturally spawning stocks or runs of fall-run Chinook salmon in Valley rivers are all dominated by hatchery salmon. Without hatcheries and straying of hatchery salmon to non-hatchery rivers (e.g., Yuba, Cosumnes, etc.), there would be almost no salmon runs of significance.

Second, there are hardly any significant locally adapted (wild) traits left to erode. River flows, water temperatures, gravel spawning beds, large woody debris, predators, and channel morphologies have become so limiting or compromising that wild salmon survival is nearly nonexistent.

Third, the “lifetime reproductive success” potential of wild fish is primarily compromised by water and fisheries management. Flows are too low, and fisheries continue harvesting much of the wild salmon production.

Fourth, the recent salmon population crashes of 2009 and 2016 are blamed by many salmon scientists on poor ocean conditions, with little regard for poor river habitat or water management as contributing factors, let alone hatcheries. By contrast, the federal Battle Creek hatchery managers knew they had to truck some of their smolt production to the Bay during the drought because of poor river conditions if they hoped for some survival and contribution to future runs.

The authors of the paper imply that hatcheries are the problem. No doubt the hatchery programs could be improved to lessen their negative effects and improve their contribution to salmon recovery. But for sure the fault is not with the hatcheries. Lack of support for hatcheries by scientists and resource agencies will dry up hatchery funding by water-user entities and make the problem worse.

The paper’s authors conclude: “There is a growing concern that salmon populations in the C[entral] V[alley] of California are becoming dependent upon hatchery supplementation, a conservation status recently identified as “mitigated extinction” Baumsteiger and Moyle 2017).” California salmon have been dependent on hatcheries for many decades. This is not a new development. Dams and diversions wiped out the wild salmon and their critical habitats, while hatcheries kept the dream going. Now scientists want to take the dream away.

Give the authors some credit for ending by saying: “Hatcheries can play a key role in the recovery of wild stocks, supplementing the fishery, and the reestablishment of natural areas, but only with cautious and appropriate management.” Despite the ambiguity, I had similar recommendations for improving hatchery programs in a recent post. 1