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Sediment and steelhead in the Alameda Creek basin: a review

Sediment and steelhead in the Alameda Creek basin: a review. Gordon Becker, Center for Ecosystem Management and Restoration (CEMAR). Challenges to steelhead. Migration impediments. Duration of flows ( à la “good days”). High growth rearing habitat. Ocean survivorship. Juvenile O. mykiss.

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Sediment and steelhead in the Alameda Creek basin: a review

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  1. Sediment and steelhead in the Alameda Creek basin: a review Gordon Becker, Center for Ecosystem Management and Restoration (CEMAR)

  2. Challenges to steelhead • Migration impediments • Duration of flows (à la “good days”) • High growth rearing habitat • Ocean survivorship

  3. Juvenile O. mykiss

  4. Steelhead smolt

  5. Elevated sedimentation impacts • Migration hinderance • Spawning area degradation • Reduced rearing capacity

  6. Migration impediments Direct: Migrating salmonids avoid waters with high silt loads, or cease migration when such loads are unavoidable (Cordone and Kelley 1961) Likely indirect: Silt dominated substrate of lower Alameda Creek may provide a lesser-defined thalweg and fewer velocity refugia than “natural” bedload channel

  7. Alameda Ck near lower inflatable dam, u/s view

  8. Ladder efficiency? Arroyo las Positas fishway

  9. Spawning areas In an OR stream, only about 8 percent of total area suitable for coho spawning (Bjornn and Reiser 1991) In an Eel River tributary, only 2.2 percent of the channel bed provided spawnable habitat-- largely tails of plunge pools and glides (Trush 1991)

  10. Spawning areas (2) Smothering: Intrusion and accumulation of fine sediments into redds reduces embryo survival through decreased dissolved oxygen and water exchange and impeded emergence (Swanson et al. 1987; Chapman 1988) Scour: “Increased sediment transport as a result of…greater sediment supply should increase the average depth of scour…in channels” (Montgomery et al. 1998)

  11. Reduced rearing capacity Thermal refugia: Reduction of pool area or volume in a small ID stream resulted in a reduction of summer [rearing] capacity proportional to the percentage area or volume lost (Bjornn et al. 1977)

  12. Little Yosemite pool

  13. Reduced rearing capacity (2) Foraging efficiency: Juvenile coho salmon… exhibited significant avoidance when turbidity exceeded a threshold that was relatively high (>70 NTU) (Bisson and Bilby 1982) Velocity refugia: Recent LFAs suggest juveniles “blown out” of San Francisquito and San Geronimo Creeks (J&S 2004; Stillwater 2004)

  14. Stonybrook Creek, u/s view

  15. Reduced rearing capacity (3) “As interstitial refuges and prey declined, steelhead spent less time sheltering behind or under cobbles and more time actively swimming (Power 2003)” “…steelhead confined to channels with higher levels of sediment experienced lower food availability… (Power 2003)”

  16. Sedimentation rates are key to steelhead recovery in AC

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