Scientific Investigations Report 2006-5111

Scientific Investigations Report 2006-5111

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Data Limitations and Potential Future Investigations

Based on several metrics and an overall IBI of the lower Boise River, the fish community upstream of the Lander WTF is similar to that of least-disturbed rivers in southern Idaho. Downstream of the Lander WTF, the apparent range expansion of sculpin over the last decade may indicate long-term improvements in water quality. However, important limitations apply to the analysis of this limited dataset. The main analytical tools, an IBI model to evaluate the overall fish community and relative weight equations to evaluate fish community “health,” are useful but crude in their predictive power to asses the effect of pollutants on the fish population.

Future assessments of status or changes in fish community and health in the lower Boise River would benefit from more robust assessments of the distribution of benthic species such as sculpin and direct assessment of fish health. Measures related to energy expenditure, energy storage, and survival of fish populations can be obtained with little additional effort (Munkittrick and McMaster, 2000). Measures of bioaccumulation and biomarkers of chemical exposure can be important measures for waters that receive complex point and non-point discharges. These measures have been successfully used in the monitoring and assessment of fish health in rivers receiving organic effluents and in targeting similar species found in the lower Boise River (Kloepper-Sams and others, 1994a, 1994b; Swanson and others, 1994; Gibbons and others, 1998).

Recent studies have shown that rivers receiving urban and agricultural effluent, such as the lower Boise River, may be influenced by wastewater chemicals that include detergents, disinfectants, fragrances, fire retardants, nonprescription drugs, and pesticides (Barnes and others, 2002; Kolpin and others, 2002; Sprague and Battaglin, 2004). Some of these chemicals may mimic hormones, causing effects in fish that may not be obvious in conventional monitoring, such as reduced reproductive health or reduced defense against disease (Thorpe and others, 2001; van der Oost and others, 2003; Brown and others, 2004). Three sites on the lower Boise River (downstream of Diversion Dam, upstream of Middleton, and downstream of Parma) were selected as part of a national assessment of wastewater chemicals (Barnes and others, 2002). Results of this study found no antibiotics or human pharmaceutical compounds at these sites in water but did detect hormones and other organic wastewater chemicals. Bioaccumulation of these chemicals is unknown in the lower Boise River. Preliminary results of a recent USGS study have identified these types of chemicals in Colorado streams (Sprague and Battaglin, 2004) and have indicated their potential endocrine disruption effects on fish. The USGS conducted a reconnaissance of endocrine-disrupting compounds in rivers across the United States and concluded that sites containing these compounds may affect the endocrine system of resident fish (Goodbred and others, 1997). In a survey of fish contamination in the Columbia River, mountain whitefish tended to have higher concentrations of mercury and some pesticides than did other fish (U.S. Environmental Protection Agency, 2002). This finding suggests that different species also may have different uptake rates and reactions to pollutants. Considering the above factors, a more comprehensive evaluation of fish health that includes both indicators of exposure and potential effects of endocrine-disrupting chemicals could provide important information about the effects of pollutants on fish populations in the lower Boise River.

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