Delta fish species plunge amid drought

California’s ongoing drought marked a setback for five important fish species in the Sacramento-San Joaquin Delta in 2014, including the Delta smelt, a signature native fish that has often altered the course of state water policy.

The smelt recorded an all-time low population number in an annual fall survey of fish species. Others in steep decline include longfin smelt, American shad, threadfin shad and striped bass.

The results are not unexpected because all the species are known to decline in drought years. That’s because they depend on ample freshwater outflow to support their habitat, and such flows decline during drought. The fish have long been affected by water diversions from the estuary to serve California’s human population, as well as factors such as pollution, habitat loss and invasive species.

Drought adds to the strain. For instance, water was held back in Shasta Lake to ensure enough water for people and for salmon runs. That water thus became unavailable to provide flow through the Delta when it was needed earlier in the year for resident fish like smelt.

This story was originally published January 14, 2015 at 9:30 PM with the headline "Delta fish species plunge amid drought."