M2 AM Aquatic Ecotoxicology (Part 1)
Monday, 14 November 2005: 8:00 AM - 11:40 AM in Ballroom 2

(HAR-1117-033567) Effects of Non-point Source Contaminants and Water Quality on Fishes in Agricultural Receiving Streams.

Harkenrider, T¹, Gillespie, R¹, ¹ Indiana University-Purdue University Fort Wayne, IN, USA

ABSTRACT- The objective of this study was to assess sublethal effects of contaminants from agricultural runoff on fish growth, health, and reproduction. It was hypothesized that non-point source toxicants would cause demasculinizing endocrine disruption. Blacknose dace and creek chubs were collected from two contaminated streams. Whole blood in chubs from the high contaminant site averaged 47% hematocrit, while chubs from the low impact site and dace from both sites averaged 54-60% hematocrit. Vitellogenin (vtg) levels in males for both species were greater at the high contaminant site (6373 ng/ml vtg) than the low contaminant site (737 ng/ml vtg). Mass, length, condition factor, liver somatic index, and gonadosomatic index did not differ for either species between sites. In laboratory bioassays, fathead minnow larvae were exposed to stream water for 30 days, followed by five months in tap water. Fish exposed to stream water were initially smaller (2.5-6.8 mg) than references (5.0-6.9 mg), but the effects were not evident after subsequent transfer to tap water. Although exposure to stream water significantly affected larval and juvenile mortality (12-76%) compared to references (6-14%), vitellogenin production was not induced in larvae. There was little to no effect on liver somatic index or gonadosomatic index in adults. Sexually immature fish comprised 15% of the reference population, 21% of the low contaminant treatment, and 28% of the fish in the high contaminant assays. Of mature adults, 49% of the reference fish, 31% of the low contaminant treatments, and 46% of the high contaminant treatments were anatomically female. Laboratory results and field data indicate that low levels of non-point source agricultural contaminants may affect sexual differentiation and growth in larvae, whereas higher contaminant levels result in increased mortality and vitellogenin induction in adult male fish.

Key words: endocrine disruption, non-point source pollution, agrochemicals, fishes