Ear bones of fish revealed “diary of selenium exposure” that was key to unraveling the mystery.
Captured in the wild and raised in tanks at UC Davis, Sacramento splittail show spinal deformities traced to exposure to selenium. Scientists used the fishes' ear bones, called otoliths, to track their exposure to selenium. Photo: Fred Feyrer/U.S. Geological Survey; fish in Rachel Johnson’s hands.
Native fish discovered with spinal deformities in California’s Sacramento-San Joaquin Delta in 2011 were exposed to high levels of selenium from their parents and food they ate as juveniles in the San Joaquin River, new research has found.
The finding published in Environmental Science and Technology indicates that some fish in the region may experience harmful levels of selenium. Selenium is a naturally occurring mineral that is essential to life but turns toxic and can cause deformities at high levels. Deformities were also found in birds exposed to selenium concentrated in agricultural runoff in the same area in the 1980s.
X-ray image of three Sacramento splittail with varying types of spinal deformities. The ear bones of the fish —visible in the x-ray as bright round bones marked by arrow—held a record similar to tree rings showing when in their lives they were exposed to elevated selenium linked to the deformities. Photo: Betty Ma, UC Davis Veterinary Services.
Biologists collected the juvenile fish, minnows known as Sacramento splittail, from a pumping station in the Sacramento-San Joaquin River Delta in 2011. They soon realized that more than 80 percent of the approximately 1,000 collected fish exhibited spinal deformities.
“This was not just a few fish, it was the majority of them,” said Fred Feyrer, a research fish biologist at the U.S. Geological Survey’s California Water Science Center and co-lead of the research.
FUll story: https://www.fisheries.noaa.gov/feature- ... ovdelivery
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