Monday, February 8, 2016

He or She or It

Timothy Knepp - US Fish and Wildlife Service
Sex change is in the news a lot and now the fish are joining in.  National Geographic describes the findings in Vermont's Missisquoi National Wildlife Refuge.
"About 85 percent of male smallmouth bass collected in national wildlife refuges in the Northeastern U.S. had eggs growing in their testes. Pollutants that mimic sex hormones are the suspected culprit."
Eggs?  Well shut my mouth! - Bill Roston
Scientists studying fish in 19 national wildlife refuges in the U.S. Northeast have found that 60 to 100 percent of male smallmouth bass had testes growing female egg cells.  This condition called intersex is not new but the increasing frequency is alarming.  It had previously been described in a Science Friday story back in 2006 and examples were known from the 1990s.

The suspected culprits are endocrine disrupting chemicals (EDC) entering the watersheds.  These can be found in pesticides, electronics, personal care products and cosmetics.  Chemical contaminants of concern include estrogens from birth control pills, the plasticizer bisphenol A, and the herbicide atrazine.  Laboratory studies of the diabetes drug metformin, using levels found in Lake Michigan water, has been shown to produce intersex fish.

Intersex changes have previously been documented in alligators, soft-shelled turtles and frogs.  Studies in Europe have shown that fish with eggs in their testicles tend to produce less sperm which have reduced motility, leading to reduced reproductive rates.

We have no studies from our Ozark streams where our smallies reside.  Studies in Northeastern US waters have shown a much lower incidence of intersex fish among largemouth bass populations, a hopeful note for fishing on the White River lakes.  One more reason to keep our waters clean.

Keep up on the latest on the Upper White River status with Ozarks Water Watch.

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