Longfin smelt, Spirinchus thaleichthys, is a local species of smelt native to the northern Pacific coast of North America. You can find these fish in the Sacramento-San Joaquin Delta. They are known for their long pectoral fins, a pair of fins located on each side just behind the gill openings, which reach almost to the pelvic fins. The upper jaw line reaches back towards the eye while the lower jaw projects in front of the upper jaw. Adult longfin smelt are typically 3.5-4.3 inches, but older females can grow up to 5.9 inches long!
The longfin smelt population in the Delta is separated from other longfin smelt populations by ocean circulation. This population is at a historic low and is therefore considered a threatened species on the California State level. Even though a study has concluded the need for this protection, there are other “higher priority” listings of species and it will be a little while until these species are put on the Federal Endangered Species list.
For an in-depth explanation of this longfin smelt study, watch this video: