Delta smelt

Overview

The delta smelt is an endangered slender-bodied smelt, about 5 to 7 cm long, in the family Osmeridae. Endemic to the upper Sacramento-San Joaquin Estuary of California, it mainly inhabits the freshwater-saltwater mixing zone of the estuary, except during its spawning season, when it migrates upstream to fresh water following winter "first flush" flow events. It functions as an indicator species for the overall health of the Delta's ecosystem. Delta Smelt are usually found at temperatures of less than 25 °C and prefer temperatures of around 20 °C. They are euryhaline but occur mostly at salinities of 0–7 practical salinity units.

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