Feminized cod on the high seas

From Baltimore, at a meeting of the Society of Environmental Toxicology and Chemistry

Male cod in the open ocean are producing vitellogenin, an egg-yolk protein ordinarily made only by females.

Vitellogenin "is a highly specific indicator of a fish's exposure to estrogens"—female sex hormones—as well as to pollutants that mimic them, notes Alexander P. Scott of the Centre for Environment, Fisheries and Aquaculture Science in Weymouth, England. Research has shown that the livers of male fish can make the quintessentially female proteins, but that typically occurs in males swimming near treated-sewage outflows (SN: 6/17/00, p. 388: Excreted Drugs: Something Looks Fishy).