Environmental Science

Fish Fatalities in the Field

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Science  15 Jun 2007:
Vol. 316, Issue 5831, pp. 1542
DOI: 10.1126/science.316.5831.1542c

Municipal wastewaters contain an enormous variety of chemicals, and fish located in downstream waterways have been reported to show alterations in reproductive endocrine function. Such male fish express proteins, such as vitellogenin, that are naturally found in the female reproductive system, and these males have been shown to develop early-stage eggs. It has been proposed that natural or synthetic estrogens in the water may contribute to the feminization of male fish, and controlled laboratory studies support this claim. Kidd et al. describe in detail a whole-lake analysis of wild fathead minnows that have been exposed to low concentrations of estrogens. The results, which span seven years, reveal that when the synthetic estrogen 17α-ethynylestradiol (as used in contraceptive pills) was added to a lake in northwestern Ontario, levels of vitellogenin mRNA and protein increased, and male fish showed arrested testicular development in comparison to fish in nearby untreated lakes. Intersex fish—that is, males with primary stage oocytes—were observed, and female fish showed elevated vitellogenin and displayed delayed ovarian development. Furthermore, though it is common to see fluctuations in wild fathead minnow populations, the experimental population collapsed after the second season of estrogen addition. This work demonstrates that chemicals like those that are detected in municipal wastewaters can affect wild fish reproduction and population sustainability. — BAP

Proc. Natl. Acad. Sci. U.S.A. 104, 8897 (2007).

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