Finding openings to balance flood protection and fish in the Lower Fraser
Presentation Abstract
Tidal creeks in large coastal deltas, such as the Lower Fraser River, can be important habitat for fish, but are often highly modified by human activities. Connectivity between tributary creeks and mainstream channels is often constrained by structures such as dikes and floodgates, designed to protect urban and agricultural areas from flooding. While playing important roles in flood mitigation, floodgates have been shown to diminish habitat quality and block fish from accessing tidal creeks. It is likely that floodgates differ in their operations and may consequently open for different amounts of time, however, these data are currently lacking. We ask the question – how does the mechanical functioning of these floodgates affect fish communities in tidal creeks? We studied 22 tidal creeks in the Lower Fraser region. At each site, we quantified floodgate operation, using time-lapse cameras to determine timing and duration of gate openings. We found substantial variation in the opening patterns of floodgates throughout the region, with some floodgates remaining closed for weeks and others opening daily. While a majority of floodgates opened infrequently, there were several sites with floodgates opening for more than half of the day on average. In addition, we sampled fish up and downstream of floodgates to assess how floodgate openness relates to fish community differences. We found that floodgates that seldom opened were associated with greater differences in fish communities and with reduced upstream native species richness by about one species on average. Where floodgates typically opened for longer periods of time, however, native species richness and fish communities were more similar in upstream and downstream reaches. Thus, improvements in floodgate operation will likely translate into benefits for fish communities. These data can help prioritize restoration activities and inform management to balance fish and flood protection in the Lower Fraser River.
Session Title
Flood Management, Climate Adaptation and the Environment in the Salish Sea
Conference Track
Climate Change and Ocean Acidification
Conference Name
Salish Sea Ecosystem Conference (2016 : Vancouver, B.C.)
Document Type
Event
Start Date
2016 12:00 AM
End Date
2016 12:00 AM
Location
2016SSEC
Type of Presentation
Oral
Genre/Form
conference proceedings; presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Fishes--Migration--Environmental aspects--British Columbia--Fraser River Delta; Fishways--British Columbia--Fraser River Delta; Conservation of natural resources--British Columbia--Fraser River Delta
Geographic Coverage
Salish Sea (B.C. and Wash.); Fraser River Delta (B.C.)--Environmental conditions
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Finding openings to balance flood protection and fish in the Lower Fraser
2016SSEC
Tidal creeks in large coastal deltas, such as the Lower Fraser River, can be important habitat for fish, but are often highly modified by human activities. Connectivity between tributary creeks and mainstream channels is often constrained by structures such as dikes and floodgates, designed to protect urban and agricultural areas from flooding. While playing important roles in flood mitigation, floodgates have been shown to diminish habitat quality and block fish from accessing tidal creeks. It is likely that floodgates differ in their operations and may consequently open for different amounts of time, however, these data are currently lacking. We ask the question – how does the mechanical functioning of these floodgates affect fish communities in tidal creeks? We studied 22 tidal creeks in the Lower Fraser region. At each site, we quantified floodgate operation, using time-lapse cameras to determine timing and duration of gate openings. We found substantial variation in the opening patterns of floodgates throughout the region, with some floodgates remaining closed for weeks and others opening daily. While a majority of floodgates opened infrequently, there were several sites with floodgates opening for more than half of the day on average. In addition, we sampled fish up and downstream of floodgates to assess how floodgate openness relates to fish community differences. We found that floodgates that seldom opened were associated with greater differences in fish communities and with reduced upstream native species richness by about one species on average. Where floodgates typically opened for longer periods of time, however, native species richness and fish communities were more similar in upstream and downstream reaches. Thus, improvements in floodgate operation will likely translate into benefits for fish communities. These data can help prioritize restoration activities and inform management to balance fish and flood protection in the Lower Fraser River.
