Delta smelt has cost valley farmers, rural communities, and residents in Southern California significant quantities of water.  Since water supplies have been restricted to protect delta smelt starting in 2008, no estimate of the water cost has been produced, but it is very likely that the total number exceeds 10-million-acre feet. The cost to replace that water is in the order of $5 billion.   Delta smelt are a small, native fish, found only in the Sacramento-San Joaquin Delta and westwards to the Napa River in salinity that ranges from slightly salty to one third that of sea water. They were listed as threatened in 1993 and the status was later changed to endangered. Since 2017, they have no longer been found in long-running fish surveys in which they were once abundant. Their protection under the Endangered Species Act is warranted.  
—Written by Scott Hamilton, president of Hamilton Resource Economics