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:
- 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).
- 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.
- 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.
- 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.
- 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.
- Natural selection continues to adjust to human influences, albeit in competition with hatchery domestication.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- Mitigation hatcheries should be converted to conservation hatcheries. The hatchery programs need a cleansing. Also, hatchery rainbows released above dams should be marked.
- 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.
- 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.
- Flows are needed to improve attraction of adult migrants to spawning rivers. Again, steelhead need the flow pulses.
For more on steelhead see: