Disoriented little fish

In early 2020, fish hatcheries in California started noticing abnormal behavior and high mortality in their salmon fry, leading to concerns that a disruption in the marine ecosystem may be affecting the transmission of thiamine, a critical nutrient, from females to their eggs (shown hatching here) and subsequently to juvenile fish. Photo by Randall Benton/Sacramento Bee/Zuma Press/Alamy Stock Photo

The Ocean’s Mysterious Vitamin Deficiency

A puzzling lack of thiamine is disrupting some marine ecosystems.

Disoriented little fish caught the attention of staff members at the Coleman National Fish Hatchery in Red Bluff, California, in early January 2020. Looking down into the outdoor tanks, called raceways, the facility’s employees noticed that among the dark, olive-colored clouds of live fish, there were occasional slivers of silver from the undersides of tiny fry that were struggling to swim. The fish would roll onto their sides, sink to the bottom for a moment, spring back upright, swim a few strokes, and then roll over again.

Many were dying, too. While a few hundred mortalities daily in a facility containing millions of fish is normal, something was definitely amiss.

“[Mortality] was in the thousands, and it didn’t go down,” says Brett Galyean, project leader at the hatchery.