Trinity River Salmonid Life Histories What we know, and what we need to know

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Trinity River Salmonid Life HistoriesWhat we
know, and what we need to know
Trinity River Salmonid Life Histories What we
know, and what we need to know
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Life Histories that we know

• Chinook salmon spawn between mid September and
  December.
• Chinook fry emerge from the redds starting early
  January through March.
• Coho salmon spawn from November through December/
  January.
• Coho fry emerge starting in February and continue
  through March/April.

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Life Histories that we know (continued)

• Steelhead spawn from January- March.
• Steelhead fry begin emergence in March and
  continue through May.
• 60 of all spawning occurs in the first 3 miles.
• The highest concentrations of fry/juveniles occur
  in these first few miles.
• Salmonid fry seek out shallow, slow velocity
  habitats that include cover.

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Valued Cover Types

• Chinook, coho and steelhead fry can all be found
  rearing in similar habitats. They prefer
• Woody debris
• Grasses
• Exposed roots
• Aquatic vegetation
• Young willows

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How can we maximize juvenile survival/production

• Provide sufficient habitat (velocity cover and
  escape cover) for rearing salmonids

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Trinity River Flow Evaluation

• Used a 1-D PHABSIM model to determine recommend
  flow regimes
• Cover was not included in the suitability index
• Recommended a 300 cfs release will provide
  suitable microhabitat and macrohabitat for
  spawning and rearing fish in the Trinity from
  Lewiston Dam North Fork Trinity River in the
  current channel morphology.

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2006 Trinity River Lewiston Dam Releases
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What do we see

• High numbers of juvenile chinook, coho and
  steelhead (0) rearing the upper 5-10 miles
  throughout the winter and spring months
  (including the spring hydrograph).
• Lower numbers of rearing fish in the other 30
  miles through the same time period.
• Fry/Juvenile fish staying close to cover (both as
  a velocity break and for escape cover).

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What we dont see

• 1 and 2 natural steelhead rearing in the first
  5-10 miles.
• Large numbers of overwintering coho salmon
  rearing in the mainstem.
• Juvenile fish rearing in the deeper open water
  (Jan-May). The exception being Chinook in the
  summer months (after 4 million hatchery juveniles
  have been released).

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Key Points to Consider

• The upper 5-10 miles is our headwaters.
• Juvenile fish NEED velocity/escape cover.
• What effects are hatchery fish/brown trout having
  on naturally rearing fish? Where are the
  overwintering coho and steelhead?
• How can we maximize rearing habitat in the
  headwaters where it is needed most (addition of
  gravel, woody debris, and/or higher base flows)?
• Should the headwaters be treated differently
  when considering rehabilitation actions?

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