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Wednesday, January 27 • 11:00am - 11:20am
The Relationship Between Suspended Sediment, Discharge, and Recruitment of Smallmouth Bass Micropterus Dolomieu In The Eel River, Indiana

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AUTHORS: Kyle Boone*, Central Michigan University; Kevin Pangle, Central Michigan University; Jerry Sweeten, Manchester University

ABSTRACT: Changes in land use can be a driving a force for increased rates of soil erosion. Consequent sediment loading in streams has been recognized as a major, negative factor to cold water (i.e. salmonid) fish populations, but less is known about its impact on warm water fish species. We evaluated the effect of total suspend sediment (TSS) on the population dynamics of a warm water species, smallmouth bass Micropterus dolomieu (SMB), in the Eel River (Indiana), an intermediate sized Midwestern stream. From 2006 to 2015, we measured physical characteristics of the river and observed the behavior of SMB during their nesting period (1 May to 30 June). For each year, we estimated population density and age-structure using electrofishing survey data. We found a significant, negative relationship between relative abundance of age 3+ SMB and mean TSS experienced during nesting the year age 3+ fish were born. Previously, discharge has been thought to be a determining factor in SMB recruitment so we also related recruitment to mean discharge experienced during the nesting period. We found that the relationship between mean discharge and the relative abundance of age 3+ SMB was insignificant. The trends we saw with recruitment were further supported by SMB behavioral observations, where mean TSS was a significant, negative factor on number of nests, but not discharge. To the best of our knowledge, this study provides the first evidence of TSS, more so than discharge, negatively impacting SMB recruitment. We believe that the negative impact on SMB populations is likely due to increased rates of mortality in the larval stage brought on by exposure to high concentrations of suspended fine sediment consequently reducing foraging success. It is likely that the same phenomenon is occurring in other Midwestern streams where agriculture is the predominate land use within the watershed.

Wednesday January 27, 2016 11:00am - 11:20am EST