Friday January 13, 2023

Hakai Magazine

Conservationists have spent decades trying to prevent the extinction of the delta smelt, a tiny transparent fish that smells vaguely of cucumbers. The funky fish is native to California’s San Francisco estuary, a series of bays and river deltas covering more than 4,000 square kilometers between Sacramento and the Golden Gate Bridge. The delta smelt was once the most abundant fish in the estuary but is now approaching extinction, with few fish left in the wild. Over the past two years, scientists have surveyed the estuary thousands of times but caught just one wild fish.

In December 2021, researchers at the University of California, Davis, started to experimentally release hatchery-reared delta smelt into the wild. The California Department of Fish and Wildlife (CDFW), which oversees the project, hopes the experiment will boost numbers, giving people more time to address the root causes of the fish’s decline, which include pollution, invasive species, and habitat loss caused by dams and agriculture.

However, mere months into the project, fish ecologist Levi Lewis and laboratory technician Jonathan Huang, both then at the University of California, Davis, noticed something fishy about the hatchery-reared delta smelt that raises questions about the project’s effectiveness.

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