Central Valley Steelhead 2021

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.

Longfin Smelt – 2020

In a February 2020 post on the status of longfin smelt, I lamented the poor 2019 population index (Figure 1) and thus made a grim prediction for the future of the Bay-Delta sub-population of this state-listed endangered species.  The index in wet year 2019 should have been 10 times higher (one higher in log number).  Preliminary survey results suggest that the 2020 population index for longfin smelt will likely be as poor as those in 2018 and 2019.

In Figure 1 below, the 2020 index will likely show as a red 20 just above the red 14.  Most of the 2020 spawners came from the 2018 spawners (green 18 in Figure 1).  Like the 2018 spawn, the 2020 year class grew up in a drier year, upstream in Suisun Bay and the western Delta (Figure 2), as compared to a more western Bay distribution like wet year 2019 (Figure 3).

I am very concerned what will happen if winter 2021 stays dry and there are thus two dry water years in a row (2020 and 2021).  This would drive the 2021 production index down to 2015-16 levels.  Coupled with the absence of Fall-X2 flows in 2020 and the unusually low 2019 longfin index, a second straight dry year presents a serious threat to the population index in 2021 and future years.

Figure 2. Longfin smelt catch distribution in 2020 Survey 1 of 20-mm Survey. Delta outflow was 8,000-20,000 cfs. Source.

Figure 3. Longfin smelt catch distribution in 2019 Survey 1 of 20-mm Survey. Delta outflow was 160,000-180,000 cfs. Source.


Delta Smelt – 2020 Status

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.