With Salmon Season Closed for 2023, the Work is Just Beginning

The final rules adopted by NOAA Fisheries and California Department of Fish and Wildlife this spring will be much different than last year’s rules.  The 2023 commercial and sport fishing closure is designed to ensure that adequate numbers of fall run salmon, the primary stock of the fishery, return to spawn this year and  begin the recovery of the population to allow future fisheries.  The Pacific Fisheries Management Council (PFMC) and the California Fish and Game Commission are taking this extreme action as their authorized contribution to the recovery of collapsed California’s salmon populations.  This year’s salmon closure follows yet another three-year drought (2020-2022) and associated water mismanagement.

But the work does not stop at closing the season.  The legal authorities of other state and federal agencies must now kick in and do their part.  With the salmon out in the ocean now protected, the next steps are to protect broodyear 2022 that is now in the rivers and the Bay-Delta estuary, and to be ready for the return of remaining broodyear 2019 and broodyear 2020 and 2021 adult salmon that will re-enter fresh water to spawn this fall and next year.

Hatchery Production

There are 20 million or so fall-run salmon pre-smolts soon to be released this spring from the seven Central Valley salmon hatcheries.  Hatchery personnel will release these salmon to the rivers, Delta, Bay, and coast.  Where and when they do so will greatly affect how many salmon reach the ocean and return to the rivers to spawn (escapement).

The following measures if adopted will increase success:

  • Truck as many smolts as possible to the coast and Golden Gate. Hold as many as these as possible for late spring, summer, and late fall (yearling) release.
  • Limit in-Delta and East Bay releases, because to succeed they must occur in early spring when receiving waters are cool. Early spring releases are smaller fish that do not survive as well, especially if they are released near the hatcheries.
  • Coordinate river (near-hatchery) releases in spring with river and Delta inflow/outflow flow pulses and with optimal water temperature and turbidity conditions.
  • Appropriately clip all adipose fins, and coded-wire tag all smolts.
  • Track and analyze survival under varying release strategies.
  • Adopt a Parental-Based-Tagging (PBT) program to support the overall recovery program.
  • Fund and implement hatchery program facilities and operational improvements, as recommended and planned by agencies.

Natural Production

Millions of eggs will be spawned in rivers this fall, despite what may be a near-record-low number of returning adults (escapement) in 2023.  It is imperative that the young salmon hatched from these eggs survive and contribute a maximum of natural-born smolts to the ocean.  We are so lucky that Mother Nature has provided the necessary water resources this year to allow that to happen.

As it is, only 32,000 adult salmon spawned naturally in rivers last fall, compared to 300,000 just a decade ago.  The earlier 2010-2016 recovery was a great accomplishment soon after the 2007-2009 population crash, when natural born escapement was only 25,000-70,000 (see Table 1).  That recovery was brought about after two years of fisheries closures (2008-2009) and three relatively abundant water years (2010-2012).

The following measures if adopted will increase success:

  • Provide coordinated spring river flow pulses with storage reservoir releases and/or foregone water diversions (if necessary).
  • Maintain minimum flows in rivers to meet or exceed year-round water temperature standards.
  • Limit south Delta exports during natural or induced flow pulses, and otherwise follow the export restrictions required in the 2008-2009 Biological Opinion.
  • Minimize salmon egg, embryo, and fry stranding in spawning gravel beds (redds) that occur when reservoir releases are reduced after spawning has occurred.
  • Minimize stranding, entrainment, or adverse water temperature changes caused by otherwise legal water diversions.
  • Limit agricultural or municipal waste water discharges that may increase water temperature in key salmon habitats.
  • Upgrade gravel supplies in prime spawning habitats before next fall’s spawning season.

Future Fisheries

In addition to closing fisheries and limiting harvest this year, it will likely be necessary to limit harvest in 2024 and 2025.  This is because of the over-harvest in 2021 and 2022 of broodyears 2018 and 2019 (Figure 1), which will likely lead to poor returns from broodyears 2021 and 2022 (Figure 2).  Broodyear 2021 is of special concern, because, like broodyear 2020 (whose poor prognosis for 2023 escapement led to the fishery closure), broodyear 2021 reared and out-migrated in a critical drought year (2022).

The following measures if adopted will increase success:

  • Plan for a closure in 2024 to protect an expected poor return from broodyear 2021.
  • Consider as an option for the 2024 and 2025 seasons a mark-selective fishery if the measures under Hatchery Production outlined above are accomplished and show signs of being effective.

Other recommended actions

https://www.fisheries.noaa.gov/feature-story/endangered-salmon-regain-access-healthy-west-coast-habitat-through-20-projects-funded

https://wildlife.ca.gov/News/cdfw-announces-225-million-to-benefit-salmon-and-support-critical-habitat-projects-statewide#gsc.tab=0

Chinook escapement in Sacramento River

Table 1. Source: PFMC.

Graph of Sacramento Index from 1983 through 2022

Figure 1. Sacramento River fall-run Chinook salmon population index comprised of escapement (natural areas and hatchery counts) and river and ocean harvests. (Source: PFMC)

Graph recruits versus spawners

Figure 2. Author-developed spawner-recruit relationship using total escapements in Table 1. Number shown is recruit year escapement (left y-axis is log(x) minus 4 of recruits) plotted against spawner escapement (x-axis, recruitment three years prior). Actual number is shown in log scale on right y-axis. Red lines are target PFMC escapement range for fishery. Red and blue circles show recruitment difference between wet and dry years at maximum sustained yield spawner levels. (Spawner levels of 300-500 thousand levels can yield 500,000 recruits from wet years or as few as 100,000 recruits from dry years). Note poor recruitment in 2021 and even less in dry year 2022 due to over-harvest.

 

 

Central Valley Hatchery Salmon Production Is Being Wasted A Tale of Two Hatchery Salmon Smolt Release Groups

There are two common strategies for releasing juvenile salmon from  state and federal salmon hatcheries in the Central Valley.  One strategy is the release of hatchery salmon smolts at or near the hatchery where they are produced.  The other strategy is trucking the smolts from the hatchery and releasing them into the Bay.  There is much controversy and argument over the relative merits of the strategies.  There can be little argument that release into the Bay generates far more adult salmon than release near the hatcheries.

Consider what occurred with two American River release groups after their release in May 2018 and return as adults in 2020.  Release group #061465 was 669,000 fall-run smolts (3-4 inches long) that were transported 20 miles downstream from the American River (Nimbus) Hatchery and released into the mouth of the American River under the Jibboom Street Bridge.  Release group #061467 was 650,000 fall-run smolts transported approximately 100 miles downstream to net pens at the Wickland Oil Terminal for release into eastern San Pablo Bay, about 20 miles from the Golden Gate Bridge and the Pacific Ocean.

The estimated percent survival based on tag recoveries was 0.04% for group #061465 (released near the hatchery).  The estimated percent survival was 2.20% for group #061467 (released in San Pablo Bay).  The returns by locations are shown in Figures 1 and 2.  These relative results are common.

Figure 1. Returns for tag group #061465.

Figure 2. Returns from tag group #061467.

 

State and Federal Hatcheries Release Salmon Smolts to Rivers, Delta, Bay, and Coast

Hatcheries in California are releasing tens of millions of salmon smolts in 2022, per normal operations.  State hatcheries are trucking over ten million fall-run salmon to the Bay again this spring because of the drought.  State and federal hatcheries are releasing another ten million-plus fall-run smolts to the rivers near the hatcheries.

Future salmon fisheries will depend mostly on the Bay releases, because few of the hatchery smolts released to the river or wild salmon smolts will survive the journey to the ocean this drought year.  Yet even the prognosis for smolts released to the Bay is poor.  Delta outflows near 4000 cfs under the State’s TUCP will keep survival below one percent (Figure 1).

Meanwhile, the prognosis for wild fall-run smolts under the TUCP is grim as they began moving through the Delta in late April and early May (Figures 2 and 3).  The extra month of normal outflow needed to help the salmon get to the ocean would amount to about 100-150 TAF, less than 10% of what is being supplied to water users from reservoirs in spring 2022.  Is the TUCP allocation to outflow and fish reasonable?

Figure 1. Fall-run salmon adult returns to the American River hatchery from Bay releases vs Delta outflow to Bay at time of release. Years noted are percent returns for below normal years 2016 and 2018, and wet year 2017 under normal rules. Blue dots with outflow below 5000 cfs are from 2014 and 2015, TUCP years. Red line is hypothesized relationship. Returns under normal rules are approximately triple the returns under TUCP rules.

Figure 2. Red circle denotes wild fall-run and spring-run smolts passing through the Delta in late April and early May 2022.

Figure 3. Peak migration of fall-run and spring-run smolts into Bay from Delta in late April and early May 2022.

2022 Sacramento River Operations – Temperature Management Plan

So much is at stake in this water year 2022: water supplies, water quality, agricultural production, hydropower production, as well as the future of salmon, steelhead, sturgeon, smelt, and other native fishes of the Klamath and Sacramento-San Joaquin watersheds. Despite the lessons of the 1976-1977, 1987-1992, 2007-2009, and 2013-2015 droughts, the choices and tradeoffs are more difficult, and effects more significant and consequential to the fish, in 2022, the third year of the 2020-2022 drought. The State Water Resources Control Board is about to approve 2022 water operation plans for Central Valley Project (CVP) and the State Water Project (SWP). Among the most immediate effects of these plans will be the fate of iconic fisheries resources of the Sacramento and Klamath Rivers, in 2022 and beyond.

The two key elements of the plans are (1) the Sacramento River Temperature Management Plan (TMP) governing Shasta/Trinity operations, and (2) the Temporary Urgency Change Petition (TUCP) governing Delta operations. A 4/5/22 post covered some aspects of the TUCP on Delta operations, which serves to cut demands on federal and state reservoir storage in the Sacramento River watershed by lowering Delta outflow requirements. (See also CSPA and allied organizations’ protest and objection to the TUCP.)

This post covers the 2022 TMP, which focuses on Shasta/Trinity storage releases and management of Shasta Reservoir’s storage releases and cold-water pool in support of Sacramento River salmon. It starts with a review of both the hydrological and biological effects of Shasta and Trinity operations in 2021. Starting with 2021 creates context in two ways. First, it explains the severe depletion of CVP and SWP storage in 2021, which created the avoidable portion of the extreme storage conditions of 2022. Second, it describes the disastrous failure to protect fish in 2021, both as consequence of bad management and contributor to the dire conditions of fisheries in 2022.

2021 Sacramento River Operations

The predominant characteristic of 2021’s operations of Shasta Reservoir and the Sacramento River was excessive reservoir storage releases over the spring and summer for water deliveries. Within this constrained context, the dominant biological features in 2021 were management of the cold-water pool for salmon , along with associated “downstream” effects on the lower river and Bay-Delta. The 2021 Sacramento River operations plan led to significantly reduced production in brood year 2021 of all four runs of Sacramento salmon.

I have divided the 2021 story into five event periods (Figure 1), each with differing conditions and outcomes:

Period A: The early-April through early-June period was characterized by rapidly rising high releases (6000-9000 cfs) for water deliveries in late April and May. Reclamation claimed it saved 300 TAF of Shasta’s cold-water pool using power bypass of warm surface water for the high spring releases. In reality, the excessive delivery of irrigation water unnecessarily depleted total Shasta storage by nearly 500 TAF and depleted the cold-water pool by 200 TAF. Those storage losses also crippled any ability to subsequently sustain the cold-water pool through the summer.

The releases of unseasonably warmer water (56-60ºF) also (as planned) inhibited spawning in the late-April to early-June portion of the winter-run salmon spawning season (about half of the historical season). It also stressed winter-run and spring-run adults in their upper river pre-spawn holding areas. Recent scientific studies suggest that such stress (extended holding and warmer water) may have contributed to thiamine deficiencies in spawners that contributed to poor subsequent fry survival and smolt production. Rapidly rising flows and water temperatures may have also compromised late-fall-run salmon egg incubation that normally continues into April. Irrigation deliveries in the middle and upper river led to lower flows and high water temperatures in the lower river (Figures 2 and 3); this both reduced the survival of emigrating spring smolts of all four races of salmon, and hindered and stressed upstream migrating winter-run and spring-run adults.

Period B: The mid-June period of cold-water releases (53-55ºF) was designed to stimulate winter-run adult spawning. It also provided 8000 cfs irrigation releases that unnecessarily depleted total storage and the cold-water pool by 6-8 TAF per day for nearly two weeks (~100 TAF lost cold-water pool and total storage). It also resulted in salmon spawning at 8000 cfs, spawning habitat conditions that led to water surface elevations that increased by one-foot and then dropped by two-feet over the summer salmon egg incubation season. I have not assessed the role of flow on the amount of quality spawning habitat available or on the potential of redd dewatering/stranding, although such factors should also be considered in evaluating an operations plan. Irrigation deliveries in the middle and upper river led to lower flows and high water temperatures in the lower river (see Figures 2 and 3), hindering and stressing winter-run and spring-run adults that were late in migrating upstream.

Period C: The late-June to early-August period was the main winter-run egg incubation period under 2021 operations. Flow releases increased to accommodate irrigation demands. Irrigation diversions, in turn, reduced flows in the river further downstream, leading to high water temperatures (72-78ºF) that blocked early arriving fall-run adult immigrants. A rise of almost two feet in water level in early June from the increased flow likely caused some redd scouring in the upper river spawning reach below Keswick Dam.

Period D: The mid-August to mid-September period was characterized by falling storage releases, associated declining water levels, and warming water as the cold-water pool and access to it declined. Winter-run egg incubation continued through the period and likely suffered from stressful water temperatures and redd dewatering. Flows in the lower river increased, and water temperatures declined, becoming less stressful for upstream migrating adult fall-run.

Period E: The late-September through November period was characterized by continued warming of water temperatures due to lessening access to Shasta’s severely depleted cold-water pool, followed by natural fall cooling. Releases and water levels declined rapidly in the spawning reach. At the beginning of the period, warm water interrupted or delayed spring-run and fall-run spawning, while a water level drop of several feet led to redd dewatering and stranding. Winter-run fry were also subjected to potential stranding during the drop in water level. Spring-run and fall-run spawning was likely hindered or delayed into November due to high water temperatures and decreasing flows and associated water levels.

The 2022 Plan

The May 2 2022 Final TMP Is a radical change from the 2021 plan and actual operations. For the first time, Reclamation has prioritized protection of fish over irrigation deliveries to senior Sacramento River Settlement Contractors. The changes also reflect the much lower available storage in this third year of drought (Figure 4). Water release projections are much lower to sustain the cold-water pool and cool downstream temperatures through the summer (Tables 1 and 2).

April Operations and Effects

April operations closely followed the draft plan that Reclamation submitted to the State Water Board on April 6. April operations using middle TCD gates and small imports of Trinity River water maintained Keswick releases at 52-53ºC and 3250 cfs per the draft 2022 TMP. Such operation helped preserve Shasta storage and the volume of the deeper, cold-water pool (<50ºF). Valley-wide precipitation since mid-April increased flows in the middle and lower Sacramento River, stimulating juvenile salmon emigration and adult spring-run and winter-run salmon immigration. A small pulse flow from Keswick to the 30 miles of spawning and rearing habitat below Keswick Dam would have helped stimulate and benefit these salmon migrations, especially those from the upper 30-mile reach that saw little or no benefits from the April storms, but this did not occur.

The draft TMP (April 6) had the same proposed releases from Keswick Reservoir as the final TMP (May 2). However, the end-of-September storage in Shasta Reservoir predicted in the final TMP (1135 TAF) is over 100 TAF lower than was the prediction in the draft TMP (1250 TAF).

Proposed May Operations

The proposed May 4500 cfs release would come from Shasta Dam’s middle gates with access to warmer surface water in the lake, thus saving some of the cold-water pool. Such savings would require warmer releases that would delay spawning and stress holding adult winter-run and spring-run salmon.

For those winter-run who do spawn in May, egg survival could be compromised by the warmer water. With warming surface waters and warmer reservoir inflows in May, and more pre-spawn adult salmon arriving in the 10-mile spawning reach below Keswick Dam, a Keswick release temperature maintained at or below 51ºF would ensure the 10-mile spawning and holding reach is maintained near 53ºF. A colder release would require proportionately more cold water be released from deeper dam gates.

In reality, middle gate operation through early May (Figures 5 and 6) has sustained cooler-than-expected daily-average release temperatures at 51-52ºF. Hydropower peaking has accessed the warmer upper layers of the reservoir (Figures 7 and 8), saving some of the cold-water pool as planned. However, middle-gate operation under hydropower peaking, and gradual warming of reservoir surface waters, will result in increasing release temperatures per the plan later in May. A rapidly warming reservoir may necessitate use of lower gates or less hydropower peaking operations to maintain <54ºF through May per the plan. If spawning commences in early May due to cooler than planned dam releases, higher late May release temperatures would begin to compromise earlier-spawned egg survival. This should cause some re-evaluation of the plan.

Proposed June-September Operations

The proposed June-September 4500 cfs release (4000 cfs in September) from Shasta Dam will be from the lower TCD gates from the cold-water pool at ~50ºF (Table 2). Slightly higher Keswick Dam release water temperatures are predicted due to warming in Keswick Reservoir at ~4500 cfs through-flow. Water temperatures 5 miles downstream at Highway 44 will increase slightly more due to warm air temperatures.

The final temperature management strategy, based on recommendations received from the Sacramento River Temperature Task Group (SRTTG), is to target 58ºF at Highway 44 during the initial part of the season and then target 54.5ºF for 16 weeks around the estimated peak spawning date of Aug 2. This would result in targeting 54.5ºF from June 7 through September 27 or until the cold water is used up. Due to the limited available control in operating the middle gates (as described above), temperatures in June and July may be cooler than 54.5ºF. Reclamation will operate the TCD to target as close as possible to 54.5ºF to conserve cold water for maintaining target temperatures throughout the critical period.

Reclamation also received feedback from SRTTG members that an initial target of 58ºF would help to conserve cold water for later during the more critical portion of the temperature management season. The problem with this is that it will delay spawning, stressing yet-to-spawn adults and compromising survival of earlier-spawned embryos.

Fall Operations

Fall operations will be similar to those described above for Period E in 2021, with the exception of a lesser drop in flow. Water temperatures in late summer and fall will increase as the cold-water pool is depleted and access to it ends. Increasing temperatures will delay spring-run and fall-run spawning and stress pre-spawn adults (potentially aggravating the thiamine deficiency problem).

Uncertainties

The planners have noted significant uncertainties that will require intensive real-time operations and management throughout the summer to achieve the various goals and targets throughout the system. To address uncertainty, Reclamation has employed conservative estimates of future conditions in the modeling assumptions (e.g., hydrology, operations, and meteorology) and projections, and has included as part of the TMP the potential to make changes, in consultation with the SRTTG, Water Operations Management Team, and/or the Shasta Planning Group. The State Board and NMFS should be included in the decision process.

Infrastructure limitations

The 2022 TMP was developed in consideration of the limitations on using the TCD and the need for temperatures below 56ºF at the Livingston Stone National Fish Hatchery. Efforts to address these limitations should be accelerated. Hydropower peaking operations changes should also be considered.

Related Actions to the Final 2022 TMP

1. Six-Fold Increase in Winter-Run Hatchery Smolt Production
Reclamation plans to fund a six-fold increase in the production of hatchery winter-run smolts this year with staged fall-winter releases from the hatchery and Battle Creek. Such releases should timed to coincide with natural flow pulses and pulse flows from Keswick Dam.

2. Transfers of Adult Salmon
The plan includes the capture and transport of adult winter-run salmon to the headwaters of Battle Creek. Good additional measures would be to give these adult fish thiamine injections and to enhance spawning gravels in Battle Creek as soon as possible.

3. Thiamine Treatments
Stresses imposed prior to spawning (e.g., delayed spawning, low flows, warm water during migration) and holding contributes to thiamine deficiency and high mortality of yolk sac fry, both in hatcheries and wild salmon1. Only hatchery salmon can be treated effectively at adult or egg stage, so efforts should be made to treat any wild adults that are handled, as well as to minimize pre-spawning stresses (e.g., erratic flows and high water temperatures).

4. Water delivery cut to 18% to Settlement Contractors
The TMP proposes to limit water deliveries to Sacramento River Settlement Contractors to 18% of their contracted amounts. The State Board should enforce this limitation. Reclamation should subordinate the timing of water releases to contractors to the needs of salmon downstream of Keswick Dam.

5. Reduced Downstream Deliveries
Demand on Shasta storage for Delta inflow/outflow has been reduced by relying more on other SWP/CVP and non-project reservoirs. However, lower Sacramento River and Delta inflows have reached water temperatures above 65ºF in early May, which puts additional stress on salmon that are immigrating in late spring. It is not a question of whether in May or June lower river water temperatures will exceed 68ºF – the state standard – but when.

6. System-Wide Water Management
Reclamation plans to manage system water supplies to minimize demands on Shasta’s cold-water supply. The Plan and temperature modeling relies on numerous drought actions throughout the Sacramento watershed to reduce reliance on stored water from CVP and SWP reservoirs this summer. “These drought actions have added a degree of flexibility to manage storage at Shasta, Oroville and Folsom reservoirs for meeting public health and safety needs, repelling salinity in the Delta, producing hydropower and providing additional cold water for fishery protection throughout the summer.” In 2022, Reclamation has finally cut deliveries to Sacramento River Settlement Contractors substantially below minimum amounts stated in contracts, in order to protect salmon. However, DWR has not done so for Feather River Settlement Contractors. Reclamation and DWR should be looking at system-wide delivery reductions. Reclamation should also call on New Melones for Delta salinity control as needed. See also NRDC et al. Objection to the TMP (May 6, 2022) for additional recommended system measures.

7. Real-Time Adjustments and Reporting
“Daily releases may vary from these flows to adjust for real-time operations. Significant uncertainties exist within the forecast that will require intensive real-time operations management throughout the summer to achieve the various goals and targets throughout the system.” Reporting, scrutiny, and decision making should be open processes.

8. Restoration of Salmon Upstream of Dams
Reclamation is committed to restoring endangered salmon to their historical habitat upstream of Central Valley rim dams. This program should be accelerated.

Tables 1 and 2 are copied directly from the Final TMP dated May 2, 2022.

Figure 1. Keswick Dam release water release rate and temperature, April-November 2021. Five general periods (A-E) are depicted, based on flow-temperature conditions as described in more detail in text. A. Spring high storage release rate (6-9K cfs), including extensive power bypass releases of warm surface water. B. A late-June cold water release to stimulate winter-run salmon spawning (<53ºF). C. A post-spawn higher irrigation release period with late-egg-stage sustaining water temperatures. D. Cold-water pool saving period with falling flows and higher water temperatures. E. Early fall period with loss of access to cold-water pool and reduction in storage releases.

Figure 2. April-December 2021 Sacramento River flow below Keswick Dam (river mile 300) and below Wilkins Slough (river mile 120). The difference between the two locations, plus tributary and ag return inputs, equals total irrigation deliveries via surface diversions and ground water depletions.

Figure 3. Water temperature in the lower Sacramento River at Wilkins Slough (river mile 120) May-August 2021, along with average for past 13 years. Note that the state’s year-round water quality standard for the lower Sacramento River is for water temperature to remain below 68ºF. Water temperatures above 65ºF are stressful to migrating juvenile and adult salmon. Water temperatures above 70ºF hinder adult salmon migration. Water temperatures above 75ºF are lethal to salmon.

Figure 4. Shasta Reservoir storage in 2022 and other selected years.

Figure 5. Shasta Reservoir water temperature profile at end of April 2022.

Figure 6. Water temperatures of Shasta and Keswick Dam releases in 2021 and to date in 2022.

Figure 7. Hourly water temperature in Shasta Dam releases, 4/27-5/7 2022.

Figure 8. Hourly Shasta Dam flow releases 4/27-5/7 2022.

  1. Adult salmon thiamine stores reduce most during the pre-spawning fast (Vuorinen et al. 2020).  Vuorinen PJ, Rokka M, Ritvanen T, Käkelä R, Nikonen S, Pakarinen T, Keinänen M. 2020. Changes in thiamine concentrations, fatty acid composition, and some other lipid-related biochemical indices in Baltic Sea Atlantic salmon (Salmo salar) during the spawning run and pre-spawning fasting. Helgol Mar Res. 74(1):1–24. doi:https://doi.org/10.1186/s10152-020-00542-9. (Crossref), (Web of Science ®), (Google Scholar) https://hmr.biomedcentral.com/articles/10.1186/s10152-020-00542-9

Radio-Tracking Study Greatly Advances Central Valley Salmon Science

Over the past five years (2018-2022), federal and state biologists have undertaken a comprehensive study of salmon smolt migrations down the 350 miles of the Sacramento River from below Shasta Dam to the Delta, Bay, and ocean.  The study released thousands of radio-tagged late-fall-, spring-, fall-, and winter-run hatchery and wild smolts in the Sacramento River near Redding (RM 290), then tracked their progress and survival as they proceeded to Butte City (RM 170), the Tower Bridge in Sacramento (RM 60), and Benicia Bridge at the head of San Francisco Bay.  Each release group provides a story that is helping our understanding of salmon science in the Central Valley.  Most important are lessons learned about drought and climate change.  Much has been learned, with more to come.

An Example: Releases of Radio-Tagged Winter-Run Smolts

Radio-tagged winter-run salmon smolts from the federal Livingston Stone Fish Hatchery were released to the Sacramento River at Redding in winter of years 2018-2022.  Their signals were detected from Butte City to the Benicia Bridge at the head of San Francisco Bay.  For example, Figures 1 and 2 show detections from a release at Redding on 2/14/2019 of 650 radio-tagged smolts.  Figure 1 shows detections over the winter and early spring at Butte City, 120 river miles downstream of Redding.  Figure 2 shows detections at the Tower Bridge in Sacramento, 230 river miles below Redding.

Preliminary Findings

A summary of release-group survival in Table 1 indicates the following:

  • Survival was significantly compromised in dry years 2018, 2020, 2021, and 2022 compared to wet year 2019.
  • Survival was poor in the upper river and the Delta.
  • December late-fall-run releases during wet periods in generally dry years had relatively high survival.

Other findings include:

  • Smolts that received thiamine “boosts” in the hatchery had slightly higher survival.
  • Approximately 20-25% of smolts are diverted into the central Delta at Georgianna Slough
  • Survival among release groups within a year was often related to flow and/or water temperature after release (Figures 3 and 4).
  • Fall-run salmon grown in 2020-2021 at the Coleman Fish Hatchery on Battle Creek had significantly higher survival when released at Butte City than when released directly from the hatchery about 80 miles upstream of Butte City.

 

Table 1.  Percent survival summary for release groups by run and year.

Winter Run Hatchery Chinook – released at Redding

Year To Butte City To Sacramento To Bay
2018 18.4
2019 64.5 23.3 25.6
2020 25.8 13.2 3.5
2021 25.8 10.1 3.6

Late Fall Run Hatchery Chinook – released at Battle Creek Hatchery

Year To Butte City To Sacramento To Bay
2018 0.17
2019 23.5 4.8
2020 76.1 60.4 16.9
2021 36.6 14.3 4.7
2022 75.5 17.1

Battle Creek Hatchery fall run – released at Battle Creek Hatchery

Year To Butte City To Sacramento To Bay
2019 46.0 22.0
2020 36.4 9.1 0.1
2021 0.3 0.0

Battle Creek Hatchery fall run – paired study

Year To Sacramento To Bay
2021 at Battle Ck 1.7 0.0
2021 at Butte City 26.3 4.7

Feather Hatchery spring run – released in lower Feather River

Year To Sacramento To Bay
2019 49.4 26.2
2020 26.8 2.6
2021 28.6 2.2

Wild Chinook Red Bluff Release

Year To Butte City To Sacramento To Bay
2018 3.2
2021 2.2 0.0 0.0

American River Hatchery Chinook – lower American River release

Year To Sacramento To Bay
2018 68.1 2.0

Butte Creek Wild Spring Run – lower Butte Ck

Year To Sacramento To Bay
2018 27.2
2019 16.3 1.5
2021 0.0 0.0

Battle Creek Start-up Hatchery Winter Run Chinook to Battle Creek

Year To Butte City To Sacramento To Bay
2019 23.3 14.0
2020 17.5 9.4 0.0
2021 11.5 3.3 0.2

Figure 1. Detections at Butte City of hatchery winter run smolts released at Redding with flow at Butte City gage 2/14/2019.

Figure 2. Detections at Tower Bridge in Sacramento of hatchery winter run smolts released at Redding with lower Sacramento River flow at Wilkins Slough 2/14/2019.

Figure 3. Survival rate to Sacramento of wild Butte Creek spring run radio-tagged release groups with Butte Slough flow in 2018.

Figure 4. Survival rate to Sacramento of wild Sacramento River fall run radio-tagged smolts, Red Bluff release groups with lower Sacramento River flow and water temperature at Wilkins Slough in 2018.