Response of Fish Populations to Floating Streambed Wetlands

A new tool to provide wetland services is the floating streambed wetland (FSW), an active hydroponic system consisting of a polymer matrix floating substrate in which living plants are established. Water is circulated from beneath the FSW and across a streambed on the upper FSW surface, coming into contact with biofilms attached to the polymer matrix and associated root structures. Research has shown that FSW technology is efficient in removing nutrients and water contaminants, and recent manufacturer reports claim that FSW technology may also increase total fish biomass in small water bodies. We evaluated this claim using a replicated small (526 m2) pond experiment and FSWs that covered 2.3% of pond surface area. FSWs were installed and planted in August 2013, and ponds were stocked at equal densities with bluegill (Lepomis macrochirus) in October 2013 and large-mouth bass (Micropterus salmoides) in August 2014; populations were allowed to develop naturally prior to harvest in April 2016. Total fish biomass at time of harvest was 19.9% greater in ponds with FSWs than in control ponds. No differences in growth rates were observed for either species. This exploratory study suggested that FSWs can increase fish production in ponds, but further study is warranted. The high cost of FSWs would likely limit their use for strictly fisheries management purposes.

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