Fish community responses to ecosystem stressors in coastal estuarine wetlands: a functional basis for wetlands management and restoration |
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Authors: | Sharook P Madon |
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Institution: | (1) Water Resources and Environmental Management Practice, Ecosystem Planning and Restoration, CH2M HILL, Inc, 402 W. Broadway, Suite 1450, San Diego, CA 92101, USA |
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Abstract: | Functional responses of estuarine fish species to environmental perturbations such as wetland impoundment, changes in water
quality, and sediment accretion are investigated. The study focuses on the feeding, growth and habitat use by California killifish
(Fundulus parvipinnis), topsmelt (Antherinops affinis), and juvenile California halibut (Paralichthys californicus) in impacted coastal wetlands to provide an ecological basis for guidance on the management and restoration of these ecosystems.
The ecology of California killifish, Fundulus parvipinnis, is closely tied with the marsh surface, which they access at high tide to feed and grow. Field estimates of food consumption
show that killifish can increase their food intake by two-fold to five-fold by adding marsh surface foods to their diet. Bioenergetics
modeling predicts that killifish can grow over an order of magnitude faster if they add intertidal marsh surfaces to their
subtidal feeding areas. Tidal inlet closures and increased marsh surface elevations due to sediment accretion can restrict
killifish access to the marsh surface, affecting its growth and fitness. An open tidal inlet and tidal creek networks that
allow killifish to access the marsh at high tide must be incorporated into the restoration design. Topsmelt and California
halibut are also adversely affected by tidal inlet closures. Food consumption rates of topsmelt are 50% lower when the tidal
inlet is closed, compared to when the estuary is tidally-flushed. Tidal inlet closures inadvertently induce variations in
water temperature and salinity and negatively affect growth of juvenile California halibut. Tidal creek networks which consist
of channels and creeks of various orders are also important to halibut. Large halibut (>200 mm TL) inhabit deeper, high order
channels for thermal refuge, while small halibut (<120 mm TL) are abundant in lower order channels where they can feed on
small-sized prey which are typically less abundant in high order channels. Maintaining an open tidal inlet, implementing sediment
management programs and designing coastal wetlands with tidal creek networks adjacent to intertidal salt marsh habitat (for
fish access) are key elements that need to be considered during the planning and implementation of coastal wetland restoration
projects. |
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Keywords: | Salt marshes Lagoons Indicators of anthropogenic stressors Estuaries Fish ecology |
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