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Barriers for steelhead (Oncorhynchus mykiss) smolt migration through the lower flood channel of Alameda Creek

  • Author(s): Cervantes-Yoshida, Kristina
  • et al.
Abstract

Alameda Creek is one of the few remaining streams in the San Francisco Bay Estuary that has the potential to regain a viable steelhead trout population (Oncorhynchus mykiss). While great effort is underway to remove large barriers throughout the watershed, lesser known are the impacts of smaller structures in the lower reaches. The objective of my study was to determine if a decommissioned rubber dam, a check dam, and a temporary sewage pipe crossing impeded movement and/or created conditions that were unfavorable for outmigrating steelhead smolt during low flow periods. For the study I gathered data on temperature, depth, and channel form. The results showed that the rubber dam created inhospitable conditions of < 0.1 ft depth and water temperature of 20C in April across a 54 ft flat cement surface. Although the check dam and the sewage pipe crossing were less restrictive for smolt passage, all of the structures created environments that increased the risk of smolt predation. These inhospitable conditions were likely exacerbated by low flows. Gauge data from the past 33 years showed that low flows are common throughout the smolt migration period of April in the lower reach of Alameda Creek; therefore indicating the conditions observed in this study were not uncommon. Overall, the results suggest that modification or complete removal of these structures is the most viable solution to improve smolt migration success during low flow periods.

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