Urban fish show perturbed spawning cycle
From Baltimore, at a meeting of the Society of Environmental Toxicology and Chemistry
Sediment-dwelling English sole living in and around Seattle’s urban waterfront exhibit spawning anomalies that might compromise their reproductive success, a team of aquatic biologists finds. The changes indicate chronic exposure to environmental contaminants that mimic the animals’ own estrogen, the primary female sex hormone.
When roughly half the male English sole at several collection sites near downtown Seattle were found to be making vitellogenin, an egg-yolk protein typical of females, toxicologist Lyndal L. Johnson of the National Marine Fisheries Service in Seattle and her coworkers decided to examine female soles. To their surprise, fish that should have spawned roughly a month earlier—as other sole in the Puget Sound region had—were still carrying their full loads of eggs.
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To figure out why, the researchers began sampling female fish monthly, throughout a year, at two sites: the polluted downtown industrial region, known as Elliott Bay, and Pilot Point, a northern and relatively clean section of Puget Sound.
Normally, females make high concentrations of vitellogenin from October to January, as they make eggs. After the fish spawn in February or March, vitellogenin production plummets and stays low through the summer. Females caught at Pilot Point exhibited just this cycle. However, a large proportion of female sole at Elliott Bay made vitellogenin even in summer, Johnson says, with some fish inappropriately producing the protein “most of the year.” At the urban site, females matured at 1 to 2 years of age—not the 4 to 5 years typical of females at Puget Sound sites.
Johnson suspects that pollution is responsible for the odd findings. Males and females with anomalous vitellogenin production were caught near industrial plants and sewage-treatment facilities.