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Fish Assessments

Last Updated January 9, 2012


TVA is assessing all levels of the ecosystem to comprehensively evaluate whether adverse effects have resulted from the spill.  This involves monitoring communities and populations of organisms potentially exposed to ash, individual organisms comprising these groups, individual organ and tissue health, and reproduction success, which can be indicators of ash-related effects.  Results from sampling in 2010 and earlier are presented below. Results for sampling conducted during 2011 (post-dredging) will be available in spring 2012.

Fish Health and Reproduction

So far, no significant health effects (damage or injury) have been observed.  Some characteristics of fish health were generally poorer in 2009 immediately downstream of the ash spill than at upstream reference sites.  Fish health effects seem to be limited to a small area and to fish species that reside in localized areas for extended periods of time.  There was some recovery in fish health observed between 2009 (soon after the ash spill) and before dredging was complete in 2010.  Analysis of fish sampled after dredging (i.e. fall 2010; spring 2011; and fall 2011 fish collections) is expected to be available in spring 2012.

Individual-Level Assessments

Sport Fish Surveys - Physical Anomalies

TVA’s Valley-Wide Monitoring Program collected samples annually at Clinch River Mile (CRM) 2.5 from 2002 to 2005. These samples provide a historical look at fish health prior to the spill and can be used to evaluate effects following the spill.  In 2009 and 2010, black bass samples were collected near the spill, at CRM 2.5, and at Emory River Mile (ERM) 2.5 for comparison to the historical data.    Each fish was measured, weighed, visually inspected for physical abnormalities, and the results were recorded.  

A total of 695 and 661 black bass were collected during 2009 and 2010 surveys, respectively (Table 1).  Abnormalities were found in an average of 2.2% of bass collected after the ash spill in 2009 and 2010, lower than the 2002-2005 (pre-spill) average of 3.7% for CRM 2.5. Catch rates were higher at CRM 2.5 in 2009 and 2010 than historical data, and rates at ERM 2.5 were similar to the Clinch River’s long-term average of 51.2 fish/hr.  Results for sampling during 2011 (post-dredging) will be available by spring 2012.

Table 1.  Physical anomalies found in Spring Sport Fish Survey sampling in the Emory and Clinch Rivers


Selenium Concentrations in Individual Fishes

The EPA (2004) chronic criterion for selenium concentrations in whole-body fish is 7.91 milligrams (mg) of selenium per kilogram (kg) of dry fish tissue (mg/kg dry weight).  During the winter, fish eat little and lose weight so selenium can become more concentrated.  EPA therefore recommends fish tissue be monitored during the winter season if levels exceed 5.85 mg/kg during summer or fall.   
All selenium concentrations in fish tissue collected in 2009-2010 were below these EPA standards (Figure 1).   Results for 2011 (post-dredging) sampling will be available by spring 2012.
Additional information about sampling for contaminants in fish flesh is documented in the Fish Sampling Technical Memorandum.

Figure 1.  Concentration of selenium in fish collected at reference areas and Emory River miles in 2009 and 2010.   See text for a discussion of concentration standards.

Population-Level Assessments

Field Measurements

Bass populations and sizes at CRM 2.5 and ERM 2.5 following the spill were compared to four years of historical data collected at CRM 2.5.  
The graphs below compare 2009-2010 largemouth bass populations by length class to data collected prior to the spill (Figures 2A-B).   This comparison shows that the abundance of different size classes in both rivers in 2009 and 2010 was similar to the 2002-2005 averages for CRM 2.5.   In 2009, there was a greater representation of age-one fish (1” to 5”) in both rivers which suggest better than average survival of fish from the previous year’s spawn.   The graphs also show that the abundance of 13-16” bass (age 3-3+) at ERM 2.5 tended to be slightly lower than the historical averages for CRM 2.5, but other size classes typically were above average.  Results for sampling during 2011 (post-dredging) will be available by spring 2012.

Figure 2.  Size distribution of largemouth bass sampled in A) spring 2009 and B) spring 2010.

Laboratory Tests - Effects of direct exposure to fly ash on fish early development

Fathead minnows were exposed in a laboratory to filtered Emory River water from ERM 8.0 (control) and to ash-affected sediments from the Emory River.  No differences were observed between controls and fly-ash exposed embryos during short-term 7-day tests.  Preliminary results of long-term exposures also indicate no adverse effects on fish egg production. 

Community-Level Assessments

TVA developed the Valley-wide Reservoir Vital Signs Monitoring Program in the early 1990s to evaluate fish communities and provide overall TVA reservoir ecological health ratings.  Fish community data are evaluated with a multi-component scoring method called the Reservoir Fish Assemblage Index, or RFAI, that takes into account species richness, trophic composition, and fish health.

RFAI scores around the Kingston site ranged from Fair to Good, with the best scores observed nearest to the spill area (Figure 3).  Clinch River scores in 2007 were depressed, possibly as a result of a regional drought, and were still recovering in 2009.  ERM 2.5 scored better than either Clinch River station in number of native species, number of benthic invertivores, and % non-native species in 2009, and in 2010, RFAI scores and individual metric scores were similar among all sampling sites. 

Figure 3.  Reservoir Fish Assemblage Index scores at sites near Kingston.

One RFAI metric, fish species richness, measures the number of species found at specific sampling locations (Figure 4).  In all, 39 species were collected near the spill site in 2009, and 46 species were collected there in 2010. These numbers are very similar to pre-spill species richness measurements.  The greatest species richness (40) measured at one location was near the ash-impacted site at ERM 2.5 in 2010.  Variations in species richness between sampling locations was typically due to a few rarely-observed species present in small numbers.


Figure 4.  Fish species richness at sites near Kingston.


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