Defining freshwater mussel mesohabitat associations in an alluvial, Coastal Plain river

作者：Smit Reuben^*; Kaeser Adam

来源：Freshwater Science, 2016, 35(4): 1276-1290.

DOI：10.1086/688928

• freshwater mussel habitat
• mesohabitat
• side scan sonar
• Apalachicola River

Defining freshwater mussel habitat in large, turbid rivers is challenging but essential to effective conservation. Hydraulic investigations have confirmed that mussels persist in discrete flow refugia, areas where riverbed sediment is stable during high-discharge events. However, approaches to identify these patches often involve detailed field measurements or mathematical models that may limit their applications across wide spatial extents. We used low-cost, sonar habitat mapping to delineate a mesohabitat classification scheme based primarily upon variations in substrate bedforms and position within the river channel. Bedforms in sand-bed rivers function as indicators of turbulent flow and hydraulic conditions at the sediment-water interface. We used the resulting map to conduct a stratified mussel survey to assess mussel-habitat associations at multiple scales. In addition, we assessed habitat persistence by remapping a portion of the study area following flood-level discharge events and conducting a time-lapse, change-detection analysis. We found strong relationships between freshwater mussel occurrence and mesohabitat type and between mussel abundance and variables such as distance to low-flow bank, distance to unstable habitat, and distance from the river mouth. Mussels were found throughout recirculation-zone mesohabitats, areas of the channel traditionally recognized as flow refugia, but also were found unexpectedly throughout pool/outer bend mesohabitats. The sonar mapping approach identified 2x as many patches and 10x the quantity of recirculation-zone habitat in the study area than previously identified using traditional approaches. Mesohabitat boundaries changed little after flood events, further explaining the widespread occurrence of mussels throughout habitats characterized simply by their smooth/plane bedform appearance in sonar imagery. The mesoscale approach demonstrated in our study is a strategy for investigating freshwater mussels and other aquatic organisms in large, turbid rivers.

• 出版日期2016-12