2007 Fairfax County Regional Science and Engineering Fair

The abstract below was written by the student. The Northern Virginia Soil and Water Conservation District made no editorial changes.

Abstract

Large numbers of adult Smallmouth Bass have died in repeated fish kills in 2004, 2005, and 2006 in the Shenandoah River. The kills have primarily affected Smallmouth Bass. Although work has been done examining fish and water quality data, the cause of the fish kills is not known. We hypothesized that the lesions found on Smallmouth Bass are caused by a disruption of the protective mucosal barriers on the fish skin, allowing one or more opportunistic infectious agents to invade the fish skin, or by a systemic infection that could be observed in liver or gill tissue. DNA was extracted from fish tissue samples and amplified with bacterial or protist specific primers. Using Length Heterogeneity-PCR (LH-PCR) we expected to see a different microbial community in lesioned versus non-lesioned fish. The microbial communities in both lesioned and healthy fish were actually remarkably similar in mucosa and gill tissue samples. No foreign protist or bacterial community was observed in liver or lesion tissue. No bacterial or protist agent was implicated in disrupting the mucosal barrier or causing a systemic infection. Characterizing possible pathogens in vulnerable tissues or physically damaged sites should be a key part of strategy in pursuing a causative agent for the fish kills. In order to understand what is happening in the Shenandoah, this approach needs to be supplemented with more rigorous documentation of the fish kills and collection of specimens in quantities sufficient to test for a recurrent pathogen.