The U.S. Fish and Service has found that the San Francisco Bay-Delta Distinct Population Segment (DPS) of longfin smelt warrants protection under the Endangered Species Act (ESA). However, the Service is precluded at this time from proposing to add the species to the Federal List of Threatened and Endangered Species by the need to address other higher priority listing actions.
The finding, which was made after a comprehensive review of the best available scientific information concerning the species and the threats it faces, means the longfin smelt DPS will be added to the list of candidates for ESA protection, where its status will be reviewed annually.
Candidate species do not receive statutory protection under the ESA, meaning that today’s finding does not impose any new requirements or restrictions. The longfin smelt species remains listed as a threatened species by the state of California, which means that under State law the species cannot be taken without a permit from the State.
“Large distances between populations, the small size of this fish and potential obstacles to movement posed by ocean circulation patterns in coastal waters make the Bay-Delta population of longfin smelt markedly separate and discrete from other longfin smelt,” said Mike Chotkowski, field supervisor of the Bay-Delta Fish and Wildlife Office in Sacramento. “Our finding indicates that ESA protection is warranted for the Bay-Delta DPS only, not for other longfin smelt populations.”
The annual review and identification of candidate species provides the Service and other federal agencies, states, tribes, and other partners with notice of species in need of conservation, allowing them to address threats and take actions that may preclude the need for protection under the ESA. Any future proposal to add longfin smelt to the federal list of threatened and endangered species would be subject to public review and comment.
The Bay-Delta DPS is one of at least 20 populations of longfin smelt which are found in estuaries, rivers and lakes from Alaska to California. The Bay-Delta DPS is found in the San Francisco Bay-Delta which includes Suisun Marsh and San Pablo Bay. The longfin smelt is a pelagic (lives in open water) estuarine fish that typically reaches four inches in length, although third-year females may grow to almost 6 inches. The longfin smelt can be distinguished from other smelts mainly by its long pectoral fin.
Today’s finding is the result of a 2011 settlement agreement with the Center for Biological Diversity and The Bay Institute, which had challenged the Service’s 2009 finding that the San Francisco Bay-Delta population of the longfin smelt did not meet the criteria to be listed as a Distinct Population Segment under the ESA. Under the terms of the settlement, the Service agreed to conduct a range-wide 12-month finding to be submitted for publication in the Federal Register by March 23, 2012, and to reconsider the San Francisco Bay-Delta population for protection as a DPS.
The latest review of the Bay-Delta DPS found information indicating that the ability of the longfin smelt to move from the Bay-Delta population to another, or vice-versa, is much more limited than previously thought possible – if indeed the movement occurs at all. The review also identified several threats facing longfin smelt in the Bay-Delta, including reduced freshwater outflow, and a food web altered by the invasive overbite clam and ammonium contamination.
Longfin smelt were historically one of the most abundant pelagic fishes in the San Francisco Bay-Delta. However, their numbers have declined significantly in recent years. Abundance indices derived from survey data all show marked declines in Bay-Delta longfin smelt populations. Surveys indicate that longfin smelt abundance over the last decade (2000-2010) is the lowest ever recorded in the surveys’ 40-year history.
Monitoring survey data show there is a direct correlation between the abundance of longfin smelt and the timing and amount of seasonal freshwater flows in the upper estuary. When freshwater flow is decreased, longfin smelt reproduction in the upper estuary is impaired. The non-native overbite clam thrives in the brackish waters of the estuary. The overbite clam consumes large amounts of plankton, a major food source for many fish species – including the longfin smelt – and other aquatic organisms, by sucking in and filtering plankton from the water. The introduction of the overbite clam in 1986 coincides with the decline of the longfin smelt population. The Service found that entrainment, the incidental trapping of fish in water used for irrigation or similar purposes, is not a significant threat at this time to longfin smelt.
A copy of the finding and other information about longfin smelt is available on the Internet at http://www.fws.gov/cno/es/speciesinformation/longfin.html and http://www.fws.gov/sfbaydelta/