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(178) Process Modifications of Pulp Mills Reduce Masculinization of Female Mosquitofish (Gambusia affinis holbrooki).
Bradley, William1, Borton, Dennis*,1, Noggle, Jessica2, Gross, Timothy2, 1 National Council for Air and Stream Improvement, New Bern, NC, USA2 US Geological Service, Gainesville, FL, USA
ABSTRACT- Anal fins of female mosquitofish (Gambusia affinis holbrooki) have been reported to have male characteristics when exposed to pulp mill effluents. These changes have been described as indicators of the presence of androgenic endocrine disruptors. This was observed in effluent dominated streams before mill process changes. Modernization that began in the early 1990s and continued as mills met "cluster rules" have since been implemented. The effects of mill process modifications on anal-fin morphology of female Gambusia were evaluated in this study. Samples from collections in the Fenholloway R. and Elevenmile Creek, archived in the U. of Florida Museum of Natural History were examined and compared to new collections taken at the same sites. Historically, effluent at both sites has very little if any dilution. Nearly all females from one archived sample from the Fenholloway R. showed male characteristics including extension and additional segmentation of the 4th anal fin ray, terminal hooks, serrae, and blades. After process modifications the amount of extension and segmentation was reduced compared to archived samples, but remained higher than females from reference populations. Anal fins of female Gambusia in archived samples from Elevenmile Cr. were elongated and had more segments, but to date, male terminal structures have not been found. Recent samples from Elevenmile Cr. have little or no elongation or increased segments compared to reference sites. Samples of female Gambusia taken in 2000 from final pulp mill effluent treatment ponds indicate a slight but significant increase in anal ray length or number of segments at three of six ponds sampled. None of the females had anal fins that resembled males or had male terminal structures. These data indicate that recent process changes have reduced or removed the masculinization effects described in earlier studies, including fish exposed in 100% effluent.
Key words: pulp-mill, Gambusia, masculinization, effluent
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