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Florida Lake Management Society Annual Conference, Naples, Florida, June 4 – 7, 2007

Single regression analyses were performed for the following data pairs: 1) fish IBI scores versus river mile; 2) fish IBI scores versus bulk sediment total mercury concentrations; and 3) fish IBI scores versus bulk sediment methylmercury concentrations. None of the fish IBI scores varied significantly by river mile. No slope change effect was noted for the fish IBI scores indicating scores upstream were equivalent to scores downstream. The fish IBI scores fluctuate within the NFHR without regard to the total mercury or methylmercury sediment concentrations.

There are several factors that may contribute or explain the minor variability in fish IBI scores. Natural salt brine discharges occur near the site, and pH was slightly elevated in the NFHR near the site, which could lead to a reduction in the fish IBI scores at the locations near the site. In addition, fish typically prefer larger rock outcrops, submerged aquatic vegetation, and variable water depths for both habitat and cover. The locations with lower IBI scores lacked

these habitat elements, which could have adversely did not vary significantly with river location, and explained little of the observed variation in IBI

affected mercury scores.

the fish IBI scores. Fish IBI scores and methylmercury concentrations The IBI results indicate that fish

communities in the conclusions of other site closure in 1972.

NFHR studies

appear to that there


sustained and


been a steady

are improving over time, and support recovery of fish in the NFHR since the


TVA. 2005. “Protocol for conducting an Index of Biotic Integrity biological assessment.”

Updated 2005. YMA. 1989. “Index of Biotic Integrity Study, North Fork Holston River.” July 1989. ______________________________________________________________________________ NOTES

Session 4 – Page 19

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