Category Archives: Bay-Delta

Hatchery Delta Smelt 2021

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Efforts continue to gain approval for releasing hatchery-raised delta smelt in the San Francisco Bay-Delta Estuary. However, given a poor prognosis for a successful introduction, the chances of approval are not good.1  The biggest obstacle is the absence of a location to release the hatchery-raised fish that will allow their survival and thus contribute to the species’ recovery. Another problem is the potential detrimental effect on the remaining wild smelt from genetic compromise.

To me, the answer to the second issue is clear. With few if any “wild” delta smelt left on Earth, it is essential to get as many hatchery smelt out into the wild as soon as possible to save the species. Let the genetics get worked out later by Mother Nature.

Two locations for release of hatchery smelt seem most plausible: the low salinity zone in the west Delta/eastern Suisun Bay and the Deep-Water Shipping Channel in the north Delta. These are primary late spring and early summer nursery areas that are most likely to have the right habitat conditions (water temperature and low salinity) and food supply. These two locations were the last known concentrations of juvenile delta smelt (Figure 1) from the last strong adult spawn in 2012 (Figure 2).

The better of the two sites is the eastern-Bay/west-Delta location, because the ship-channel gets too warm by summer (Figure 3). In contrast, the region between Collinsville in eastern Suisun Bay and Decker Island in the west Delta is cooler and within the low salinity zone (Figures 4 and 5). A nighttime near-bottom release into cooler, deeper channel waters would give the hatchery smelt at least a minimum opportunity to acclimate to the warm Bay-Delta waters.2

Figure 1. Last known prime late spring and early summer nursery area of delta smelt (2012, 20-mm survey). Red lines denote approximate location of X2 (~2000-4000 EC) at the time.

Figure 2. Adult delta smelt catch index from monthly winter trawl surveys 2002-2021.

Figure 3. Water temperature (ºC) and salinity (EC) in spring 2020 in Deep Water Ship Channel.

Figure 4. Water temperature (C) and salinity (EC) in spring 2021 in Sacramento River channel near Collinsville in eastern Suisun Bay.

Figure 5. Water temperature (ºC) and salinity (EC) in spring 2021 in Sacramento River channel near Decker Island in the western Delta.

Drastic Measure to Meet Delta Outflow

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For seven days in mid-March 2021, the Bureau of Reclamation substantially increased Folsom Lake storage releases. Roughly, the releases tripled in volume (Figure 1). The release of over 20,000 acre-feet of water is significant for a year in which Folsom storage is not much better than it was in the worst year on record – 1977 (Figure 2).1 With the release in mid-March, the lake level dropped 3 feet. Yes, there was rain in the forecast and a decent snowpack, but certainly no flood concerns. So why? The reason was to meet state water quality requirements for Delta outflow. Delta outflow increased from 7,000 cfs to 12,000 cfs for a few days (Figure 3).

The outflow pulse was needed to meet an obscure and complicated provision in the Bay-Delta’s D-1641 Water Quality Control Plan called “footnote 11.” The footnote (Figure 4) specifies a formula for determining minimum daily Delta outflow for February through June in different water year types. The base requirement is 7100 cfs 3-day running average minimum (that was being met – Figure 3). What was not met is the requirement in Table 4 to increase Delta outflow from Feb-Jun for the general ecological benefit from higher natural Delta outflow. That requirement is met by meeting a specified average number of days of obtaining an electrical conductivity level (EC) of 2640. Since even that requirement was not met either (Figure 5), the Executive Director of the State Water Board allowed Reclamation and the Department of Water Resources not to meet it.

The primary problem with this Delta Outflow requirement is the abrupt and arbitrary way it is met. If all that is needed to relax the requirement is a “BOGSAT,”2 then all stakeholders need to be involved. Why did Reclamation place the burden primarily on Folsom Reservoir? Why did Reclamation release all the water over just a few days? The abrupt releases likely affected steelhead spawning. The lost storage will likely make salmon migration and spawning in the fall worse as well. At a minimum, Reclamation should have provided some form of notice of this major action. Reclamation should also document the effects.

Figure1. Streamflow in the lower American River at Fair Oaks gage March 8-18, 2021

Figure 2. Storage level in Folsom Reservoir in 2021. Source: CDEC.

Figure 3. Delta outflow in Feb-Mar 2021. Source: CDEC.

Figure 4.  FOOTNOTE 11 in D-1641:  Bay-Delta Water Quality Control Plan

Figure 5. EC at Chipps Island Station D10 in winter 2021.

Figure 6. Daily average Oroville reservoir release in winter 2021.

  1. Lake Oroville provided something less than 10,000 acre-ft, while Shasta Lake provided none. ↩
  2. BUNCH OF GUYS SITTING AROUND a TABLE ↩

Central Valley Steelhead 2021

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The Delta Science Program plans to host a Steelhead Workshop on February 17 – 19, 2021.  The purpose of the workshop is to “identify challenges to managing and monitoring Central Valley steelhead with the goal of identifying collaborations that are needed to improve the monitoring and science network for the species in the San Joaquin basin.”  While commendable and needed, such a workshop could and should cover the entire Central Valley Evolutionary Significant Unit (ESU), all of which must pass through the Delta on the way to and from the Pacific Ocean.

Although Central Valley steelhead science and management can succinctly be described as a mess, there are a few basic facts and misconceptions worthy of note that are useful in considering steelhead management in the Central Valley.

First, the facts:

  1. Steelhead are rainbow trout that have the genetic inclination to spend some of their life cycle in the ocean. Most rainbow trout have such an inclination, but some populations have long ago given up on that inclination (g., redband rainbow trout).

  2. In the Central Valley, all rainbow trout residing in anadromous waters are considered steelhead and are thus protected unless their adipose fins are clipped, which definitively shows hatchery origin.

  3. Rainbow trout of a wide range of origin, stocked or wild, live in or above dams in the Valley and are not designated steelhead. Some are remnants of steelhead trapped behind dams.  Other were hatchery raised or perhaps are remnants of long-ago geologically isolated populations.  Many of these non-steelhead pass over or through the dams and mix with steelhead, essentially becoming steelhead and influencing steelhead population genetics.

  4. All steelhead populations in the Valley have some degree of domestication from more than 100 years of hatchery influence and manipulation. Hatcheries (federal, state, and private) continue to influence population genetics.  Valley hatcheries have brought in eggs from many sources (g., Columbia River, coastal stocks, interior stocks such as Kamloops rainbow trout).  Hatcheries manipulated many important natural traits through selective breeding (e.g., run timing, age of maturity, growth rate).  Such changes affected the genetic integrity of locally adapted populations, adapted traits gained over thousands of generations.  Some hatchery sources were selected for traits better suited for hatchery managers or anglers than for natural diversity and population endurance.

  5. Valley steelhead come in many different breeds and colors, with distinct characteristics, traits, behaviors, and appearance. The basic breeds are often described by run timing:  winter, spring, summer, and fall, although most spawn in winter or spring.  Some examples are shown in attached figures below.

  6. Natural selection continues to adjust to human influences, albeit in competition with hatchery domestication.

Some misconceptions:

  1. Hatcheries are managed for benefit of natural, wild, or native steelhead populations. No. Hatcheries are managed to meet mitigation smolt production quotas at minimal cost, with some consideration for angler preferences (e.g., trophy size).  Hatchery domestication effects on genetic integrity are severe and not lessening.

  2. Central Valley steelhead are not in danger of extinction. Wrong.  They are in danger, which is why they are state and federally listed, and why no wild (unmarked) rainbow trout can be harvested in the anadromous zone of the Central Valley.  Wild “native stocks” are rare and declining.

  3. Spawning and rearing habitat in rivers and dam tailwaters are maintained to protect wild steelhead.   Protective standards are inadequate or often unmet.  Natural spawning and rearing habitats are degraded and are further deteriorating or being lost.  Flows are too low, and water temperatures too high.

  4. Steelhead are compatible with introduced non-native sportfish. No.  Striped bass, black bass, catfish, sunfish, and American shad all prey upon steelhead – the total population effect is substantial.  Since predatory fish cannot be eradicated, the interaction between steelhead and predators needs to be managed.

  5. Climate change is the cause of declining natural populations. Though climate change is real and exacerbates harmful conditions for steelhead, blaming climate change for the decline of steelhead is just a convenient excuse.

Management needs:

  1. Improved monitoring of steelhead population dynamics is needed. Despite the angler-funded steelhead stamp program, there is minimal monitoring of adult spawners or juvenile  Screw traps are for migrating fry, but steelhead fry don’t migrate like salmon.

  2. River habitats should be restored and improved. Rivers should not be treated just as conduits from hatcheries to the ocean.  Steelhead over-summer at least one year before emigrating to the ocean.

  3. Mitigation hatcheries should be converted to conservation hatcheries. The hatchery programs need a cleansing.  Also, hatchery rainbows released above dams should be marked.

  4. Spawning habitat should be for wild, native steelhead. Steelhead sanctuaries are needed.  Every effort should be made (selective barriers) to limit access to these areas by hatchery or stray steelhead, and by migratory non-native predators and competitors such as shad and stripers.

  5. Flows are needed to increase survival of wild steelhead fry and smolts. Steelhead are genetically adapted to emigrate with the natural flow pulses of fall, winter, and spring.  Reservoirs have eliminated or reduced such flows.  Without the flows, smolts won’t migrate or survive the predator gauntlet.  Trap and hauling wild smolts around the lower river and Delta predator gauntlet is an option for dry years.

  6. Flows are needed to improve attraction of adult migrants to spawning rivers. Again, steelhead need the flow pulses.

For more on steelhead see:

Native rainbow-steelhead from the lower Yuba River. Many wild rainbow trout do not migrate, choosing to remain in the cold tailwaters of dams, where they sustain high-quality sport fisheries.

An early fall run hatchery steelhead from the lower American River in October. Battle Creek hatchery steelhead smolts were stocked in the American River for one year to determine if they would be a viable more-native alternative to the American hatchery’s coastal Eel River origin stock. They were fine sport, susceptible to dry flies.

The American River hatchery program uses coastal origin stock that spawn in winter. Many spawners enter the river in late fall when fishing is closed to protect spawning salmon. Fishing is open in winter spawning season. This female caught in January was likely actively spawning. Native steelhead are spring spawners.

Delta Smelt – 2020 Status

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In a March 2020 post, I described the status of the Delta smelt through 2019.  This post updates the status with the most recent 2020 information.  Delta smelt continue to be absent from the standard long-term surveys and their related indices.  However, some Delta smelt were collected in 2020 in selected locations of the Bay-Delta during focused intensive special surveys designed to find remaining survivors.  Larval and juvenile Delta smelt were collected in low numbers in the Bay and north Delta (Figure 1).  Pre-adult Delta smelt were also collected in summer trawl surveys (Figure 2).

The north Delta habitats where a few Delta smelt persevere continue to be plagued by constant stressful if not lethal water temperatures (Figures 3 and 4).

As I stated in a prior post, Delta smelt would benefit from increased net flows through the north Delta during the spring and summer.

Figure 1. Numbers of larval and juvenile Delta smelt collected in the spring Enhanced Delta Smelt Monitoring (EDSM) 20-mm nets. Source.

Figure 2. Numbers of pre-adult Delta smelt collected in the summer Enhanced Delta Smelt Monitoring (EDSM) Kodiak trawls. Source.

Figure 3. May through September 2020 water temperature and net tidally-filtered flow in the lower ship channel near Rio Vista. Note water temperatures fall 1-2ºC when net flows increase.

Figure 4. May through September 2020 water temperature and net tidally-filtered flow in Cache Slough near Rio Vista. Note water temperatures generally fall 1-2ºC when net flows increase.

The Delta as Salmon Nursery

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The Delta is an important nursery area for Central Valley Salmon. This fact continues to be ignored or under-appreciated. The phenomenon is fully consistent with the general science on salmon in their southern range in the eastern Pacific. Nearly all California Chinook salmon are “ocean-type,” meaning that juveniles reach the ocean in their first six months after rearing for extended periods in estuaries. To grow, young salmon fry need to rear in winter in warm productive areas of floodplains and tidal estuaries (Bay and Delta). Flood control infrastructure limits floodplain habitat except in wetter years. Water management, mainly reservoir storage, limits transport of fry to the Bay except in wetter years.

That leaves the Delta as the key nursery area in non-wet years. Thus, the state of the Delta in non-wet years largely determines the success of Central Valley salmon. Salmon smolt production to the ocean is one to several orders of magnitude lower in drier years, which is the fundamental cause of salmon run declines over the past several decades during periods of drought (Figure 1).

Getting salmon fry to the Delta, successfully rearing them in the Delta, and then getting them to the Bay and Ocean are keys to their success. Peaks between droughts, and even small runs during droughts, are driven by trucking smolts from the hatcheries to the Bay and Ocean, bypassing the Delta survival sink. Without hatchery contributions, the underlying pattern for wild-natural salmon would show drastic declines during and after droughts. Improving Delta-derived smolt production is the key to improving the wild component of Central Valley salmon.

For nearly four decades, I have been promoting Delta salmon habitat improvements.1 I have also helped show the importance of winter rearing of salmon fry in the Delta.2 I have also conducted a comprehensive review of Delta salmon rearing habitats and restoration.3 In other posts in this blog, I have offered much discussion on the role of the Delta in salmon production and survival.

The State Water Resources Control Board is in a multi-year process of updating decades-old water quality standards. Focusing on salmon as a key public trust resource is the way to go. The new standards need to assure that fry get to the Delta, do well in the Delta, and then get to and through the Bay to the Ocean.

Figure 1. Over the past several decades the Central Valley fall-run Chinook salmon has declined sharply during and shortly after three major periods of drought: 1987-1992, 2007-2009, and 2013-2016. Source: CDFW Grandtab.

 

  1. Cannon , T. C. 1982. The importance of the Sacramento-San Joaquin estuary as a nursery area of young Chinook salmon. Unpublished NMFS report. ↩
  2. http://www.fisheryfoundation.org/Reports/2005-2006%20Western%20Delta%20seine%20survey%20report.pdf ↩
  3. https://calsport.org/news/wp-content/uploads/Overview-Habitat-Restoration-in-Delta-LowRes.pdf ↩