Multi-scale variation in salmonid abundance in the Salmon Trout River, Michigan and associations with sand accumulation

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Conference Proceeding

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The Salmon Trout River (STR) hosts the last known remnant coaster brook trout population along the south shore of Lake Superior making it a focus for conservation. Surveys of fish assemblages reveal densities of juvenile salmonids in the Salmon Trout River are 20% of those in neighboring rivers. The STR is relatively low gradient with natural accumulations of fine sediments, but over the past decade watershed disturbances have increased benthic fine sediments. Increased fine bedload influence ecosystem processes and alter resource availability for food web consumers, and possibly explain the low salmonid densities in the STR. Longitudinal surveys revealed greater abundances of non-native coho salmon and rainbow trout in upper reaches, whereas native brook trout abundance was greater in lower reaches with greater sand accumulations. We conducted a smaller scale comparative study of fish assemblages in two small reaches with exposed rock substrates, and two with extensive sand accumulations. Multi-pass electrofishing surveys at this small spatial scale revealed greater juvenile brook trout and rainbow trout densities in the rock sites. Thus, associations between fine sediments and fish abundance, as well as the mechanisms driving them, appear to be scale dependent.

Publication Title

North American Benthological Society 2011 Annual Meeting