Trinity River Ecology FAQ

Please note that questions regarding flows are in the Flow FAQ while questions regarding features of TRRP rehabilitation sites are in the Rehabilitation FAQ.

What types of salmon are in the Trinity River?

The Trinity River has chinook and coho salmon, plus the closely related steelhead. Chinook salmon can also be separated into spring and fall runs. Fall-run chinook are the most numerous salmonid in the Trinity River, followed by steelhead.

What about brown trout?

While fun to fish, brown trout are not native to the Trinity River. These beautiful trout are aggressive predators that may be detrimental to our native salmonid populations.

What is the difference between hatchery-produced salmon and naturally spawned salmon?

Hatchery salmon and steelhead  that spawn in natural areas are known to decrease spawning success and reduce production of young salmon. Hatchery salmon and steelhead are meant for harvest not to spawn in natural areas. See our page on Trinity River fish for more information on steelhead.

What other factors may be causing current problems for salmon populations?

Variations in marine survival of salmon and subsequent returning adults often correspond with periods of alternating cold and warm ocean conditions.  For example, cold conditions are generally good for Chinook and coho salmon, whereas warm conditions are not. Useful information on these conditions can be found at the Northwest Fisheries Science Center page on ocean conditions.

What other factors may have caused historic problems for salmon populations?

The first known impact on Trinity (and Klamath) River salmon came from canneries operating near the mouth of the Klamath River in the mid-1800′s. Unfortunately there is very poor documentation of the impact, but there are some stories that very few fish escaped these canneries and the river may have been dominated by spring-run chinook.

Subsequently, large-scale gold mining had a variety of effects.  Water was diverted from tributaries where steelhead and coho salmon spawned. medium-scale dams and diversions were regularly constructed to allow mining access to the river bed; extensive hydraulic mining kept the river muddy most of the time (see ‘Found a New Steelhead Stream‘); and dredge mining reformed the river channel, obliterating many floodplains.

Are there other species monitored on the Trinity?

Birds, mussels, aquatic insects, frogs, and turtles have been or are currently being monitored. Many of these reports can be found on our online data port.

Why is there more moss/algae in the lower Trinity?

TRRP monitors turbidity and water temperature during the summer. TRRP does not govern any other water quality parameters. Please contact the U.S. EPA, California Department of Water Resources or the Regional Water Quality Control Board for more information about nuisance algae.

Why is vegetation important to river restoration?

Native plants play important roles in keeping river ecosystems healthy. They shade the water and keep it cool, provide refuge, filter sediments, and provide habitat for the insects that young salmonids eat.

What is the purpose of willow replanting? 

Several willow species are included in the wide variety of trees, shrubs, grasses, and native flowers that are planted at channel rehabilitation sites. Willows are common in natural riparian areas, and fast growing. They quickly reach a size that provides both cover and nesting locations for songbirds and other wildlife. Willow thickets along the Trinity were historically more diverse in species composition and structure (tree and bush willows). Our plantings try to bring some of the historical diversity back to the system.

When a rehabilitation site is initially modified (and existing vegetation removed during that modification) riverside vegetation is replanted after the modification to minimize any impact to habitat on which many migratory birds depend.

How does TRRP support riparian vegetation?

The broad TRRP goal for riparian vegetation is to “establish and maintain riparian vegetation that supports fish and wildlife.” The TRRP can achieve the riparian vegetation goal through promoting diverse native riparian vegetation on different geomorphic surfaces that contributes to complex channel morphology and high quality aquatic and terrestrial habitat.

What is TRRP doing about invasive species?

TRRP is concerned with a number of invasive species issues on the Trinity River.  Channel rehabilitation actions employ various measures to reduce weedy exotic plants.  Wetland enhancements are designed both to benefit native species such as Western Pond Turtle and to reduce the prevalence of the invasive Bull Frog.  These and other invasive species issues are a focus of the Riparian and Aquatic Ecology Work Group.



Fish Biology

Physical Sciences

Vegetation and Wildlife

Water Temperature