Sacramento Fish & Wildlife Office
External Affairs
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Contacts:
Al Donner, (916) 414-6566
al_donner@fws.gov
Summary:
The original risks to delta smelt that resulted in its population decline and listing as a threatened species in 1993 continue to exist, and the population of delta smelt remains substantially below its historical levels. Some risks have increased.
Background:
Delta smelt are endemic to the San Francisco Bay/Sacramento-San Joaquin Delta Estuary (Delta) in California. They were once one of the most common pelagic (living in open water away from the bottom) fish in the upper Sacramento-San Joaquin Estuary.
Although they are restricted to a relatively small geographic range, delta smelt use different parts of the estuary at different life history stages. They hatch, typically around May, from eggs laid 9 to 13 days earlier in the slow-moving, freshwater spawning grounds of the upper Delta and lower Sacramento River, and in Montezuma Slough near Suisun Bay. After several weeks of development, larvae are swept downstream until they reach a point (typically in Suisun Bay) where the salinity reaches about 2 to 7 parts per thousand (ppt). This is the beginning of the "mixing zone" where fresh and brackish water meet. Juvenile smelt tend to seek out that salinity level, and will grow there for several months, preferring relatively shallow open water. The mixing zone is typically located in Suisun Bay, but moves farther upstream when freshwater outflows are reduced. Federal and State water pumps can affect outflows by exporting large amounts of fresh water from the southern portion of the Delta for agricultural and municipal uses. About 1,800 smaller water diversions throughout the Delta also export water for local urban and agricultural use. Additionally, two power plants in Antioch and Pittsburg use Delta water for cooling.
Around September or October, delta smelt reach adulthood and begin a gradual migration back upstream to the spawning areas. Spawning can occur any time between February and July, but most spawning takes place from early April to mid-May, in water temperatures ranging from 7 to 15 degrees Celsius (45 to 59 degrees Fahrenheit). The eggs are thought to attach to substrates such as cattails, tules, tree roots, and submerged branches, and the spawning areas most likely contain gravel, sand, or other submerged material that is washed by gentle currents close to the main river channel. Most delta smelt die after spawning, but a small contingent of adults survive and can spawn in their second year.
Although exact population estimates are not possible to obtain for this species, relative population levels have been monitored for several decades using various net surveys and counts of adults entrained by Federal and State water export facilities. Based on those surveys, delta smelt population levels declined precipitously in 1982, leading to very low numbers from 1982 to 1991, and to their listing as a threatened species in 1993 (58 FR 12854; Moyle 2002, p. 230; CBD et al. 2006, p. 9). From 1992 to 2001, abundance levels stabilized, remaining generally low but within the bounds of pre-1980 levels. Recent surveys show another substantial drop, however, with record low abundance figures from 2002 through 2007. Bennett (2005, pp. 53, 54) conducted a population viability analysis based on population trends, and found a 55 percent chance that the smelt population would reach a "point of no return" (quasi-extinction, estimated at 8,000 fish) within 20 years.
We were originally petitioned to list the delta smelt as endangered on June 26, 1990. We proposed the species as threatened and proposed the designation of critical habitat on October 3, 1991 (56 FR 50075). We listed the species as threatened on March 5, 1993 (58 FR 12854), and we designated critical habitat on December 19, 1994 (59 FR 65256). The delta smelt was one of eight fish species addressed in the November 26, 1996, Recovery Plan for the Sacramento-San Joaquin Delta Native Fishes (Service 1996, pp. 1-195). We completed a 5-year status review of the delta smelt on March 31, 2004 (Service 2004, pp. 1-50).
On March 9, 2006, we received a petition from the Center for Biological Diversity, the Bay Institute, and Natural Resources Defense Council to reclassify the listing status of the delta smelt, a threatened species, to endangered status on an emergency basis. The petition clearly identified itself as a petition and included the requisite identification information for the petitioners, as required at 50 CFR 424.14(a). The petition contained information on changes in the status and distribution of the species, and on increased threats to the species.
In response to the petition, we sent a letter to the petitioners dated June 20, 2006, stating that we would not be able to address their petition at that time because further action on the petition was precluded by court orders and settlement agreements for other listing actions that required us to use nearly all of our listing funds for fiscal year 2006.
The petition notes that water diversions, particularly from the large Federal and State pumping stations in the southern portion of the Delta, can modify the smelt's habitat in three ways. First, they remove planktonic food organisms out of the water. Second, they diminish freshwater outflows, causing the mixing zone to move upstream and away from Suisun Bay where the best rearing habitat is located. Third, the large Federal and State pumps can actually halt and reverse flows in the southern Delta, potentially interfering with both the transport of plankton and smelt larvae downstream and with the spawning migration of adult smelt upstream.
The petition notes summer trawl net surveys showed a serious drop in juvenile smelt in the south Delta in the mid-1970s, during which time Federal and State exports from the Delta were increased. Some increases and decreases were seen during the next quarter century. However, record low delta smelt abundance figures from 2002 through 2007 indicate that these existing threats may now be more imminent than at the time of listing.
The petition presents information regarding existing and planned regulatory mechanisms and their perceived inadequacy, stating that the current export criteria in the water rights permits issued under the State Water Resources Control Board regulations allow export operations at levels that exceed those necessary to maintain healthy delta smelt populations. The petitioners state that dedications of water for the environment and of money for supplemental acquisitions of environmental water mandated in the 1992 Central Valley Project Improvement Act intended to reduce the negative impacts of the Federal water project on fish and wildlife have not been fully or aggressively implemented. The petition claims that the CALFED (joint California State and Federal government) Bay-Delta Program has been largely ineffective in addressing environmental problems in the Delta, and that its future status is uncertain.
Q. Why are you choosing to do this now?
A. We have always intended to get to this petition as quickly as possible, but our listing actions occur within the limited budget provided for listing actions. Our listing workload is dictated by actions that have a court-established due date. This study was completed as promptly as were able under those limitations.
Q. Where did we get the appropriation to do this?
A. The work on this finding was conducted within our annual appropriations.
Q. Identify any real effects that a change in status might cause or allow?
A. An uplisting from threatened to endangered would result in virtually no change in our approach or the actions we could take to assist the species because under the ESA there are few differences in treatment of species between the two categories. One difference in possible treatment of an endangered species versus a threatened species. A so-called "4d rule" (so named for the section of the ESA) permits some take of a threatened species in exchange for specific beneficial actions, but a 4d rule is not allowed for endangered species. However, there are no 4d rules in place for the smelt.
Q. Will this cause any changes in the Operation Criteria and Plan (OCAP) BO you are developing for the delta smelt?
A. The development of the BO is an entirely separate process and will not be affected by this action. Any suggestion that this 90-day finding is not coincidental would be totally incorrect.
Q. Does this mean that Service biologists now think the species is likely to go extinct in the near term?
A. The threshold for extinction is more proximate for an endangered species than for a threatened species. A 2005 viability analysis (Bennett) concluded that there is a 55 per cent chance that the smelt population would reach the "point of no return" within 20 years (quasi-extinction, estimated at 8,000 fish). However, the Service is not making an extinction prediction.
Q. What is the Service doing to help save the delta smelt?
A. The Fish and Wildlife Service is engaged in a wide variety of efforts to help the species and the Delta habitat. The Operation Criteria and Plan (OCAP) BO, which seeks to minimize or mitigate for the harmful effects on the species is one obvious effort.
The Service is also engaged in the Environmental Restoration Program (ERP) and the Cal Fed program, established in 1994, continues to generate benefits to aquatic species and may continue to do so. The Bay Delta Conservation Plan (BDCP), in which the Service is participating, also has potential for making important contributions if it conforms to the habitat conservation planning process that has worked successfully in many areas. The Service also is working on plans for a delta smelt hatchery that could contribute to long-term survival of the species. And some non-Service activities, such as the Delta Vision planning effort, offer possibilities for significant Delta restoration.
Q. Where can I get more information about the delta smelt and this proposed critical habitat designation?
A. The Service provides a substantial amount of information ion its website.
Go to www.fws.gov/sacramento and open the Delta in the Spotlight box on the home page to begin.
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Last updated: July 9, 2008
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