The longfin smelt (''Spirinchus thaleichthys'') is a

smelt Smelt may refer to: * Smelting, chemical process * The common name of various fish: ** Smelt (fish), a family of small fish, Osmeridae ** Australian smelt in the family Retropinnidae and species ''Retropinna semoni'' ** Big-scale sand smelt ''At ...

that is found in several

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

and lakes along the northern Pacific coast of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. Its most distinctive characteristic is the long

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

s that reach nearly to the base of the

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s, and thus inspire the common name. The sides are silver, with the back ranging from an olive to a pinkish shade. The upper jaw is long, reaching nearly to the posterior edge of the eye, and the lower jaw projects slightly in front of the upper jaw. Both jaws have a set of very small teeth. The

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

is incomplete, reaching back only as far as the dorsal fin. Size is limited to about 20 cm. Their principal food item is the

opossum shrimp Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in this ...

, '' Neomysis mercedis'', and species of '' Acanthomysis'', but they will also eat

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

s and other small crustaceans. In turn, they are eaten by a variety of fishes, birds, and marine mammals; for instance, they are an important prey for the

harbor seal The harbor (or harbour) seal (''Phoca vitulina''), also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere. The most widely distributed species of pinniped (walruses, eared sea ...

, ''

Phoca vitulina The harbor (or harbour) seal (''Phoca vitulina''), also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere. The most widely distributed species of pinniped (walruses, eared se ...

'', in the

Columbia River The Columbia River (Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, C ...

. Their primary habitat is the open water of estuaries, where they can be found in both the saltwater and freshwater areas, typically in the middle or deeper parts of the water column. They have been found as far north as

Prince William Sound Prince William Sound (Sugpiaq: ''Suungaaciq'') is a sound of the Gulf of Alaska on the south coast of the U.S. state of Alaska. It is located on the east side of the Kenai Peninsula. Its largest port is Valdez, at the southern terminus of the Tr ...

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S., ...

, also in

Skagit Bay Skagit Bay is a bay and strait located in the U.S. state of Washington. It is part of the Whidbey Island Basin of Puget Sound. The Skagit River empties into Skagit Bay. To the south, Skagit Bay connects with the rest of Puget Sound via Saratoga ...

Grays Harbor Grays Harbor is an estuary, estuarine bay located north of the mouth of the Columbia River, on the southwest Pacific coast of Washington (U.S. state), Washington state, in the United States of America. It is a ria, which formed at the end of the l ...

Willapa Bay Willapa Bay () is a bay located on the southwest Pacific coast of Washington state in the United States. The Long Beach Peninsula separates Willapa Bay from the greater expanse of the Pacific Ocean. With over of surface area Willapa Bay is the ...

, lower Columbia River,

Yaquina Bay Yaquina Bay ( ) is a coastal estuarine community found in Newport, Oregon, United States. Yaquina Bay is a semi-enclosed body of water, approximately 8 km² (3.2 mi²) in area, with free connection to the Pacific Ocean, but also diluted ...

Coos Bay Coos Bay is an estuary where the Coos River enters the Pacific Ocean, the estuary is approximately 12 miles long and up to two miles wide. It is the largest estuary completely within Oregon state lines. The Coos Bay watershed covers an area of abou ...

Humboldt Bay Humboldt Bay is a natural bay and a multi-basin, bar-built coastal lagoon located on the rugged North Coast of California, entirely within Humboldt County, United States. It is the largest protected body of water on the West Coast between Sa ...

, the Eel River estuary,

Klamath River The Klamath River (Karuk: ''Ishkêesh'', Klamath: ''Koke'', Yurok: ''Hehlkeek 'We-Roy'') flows through Oregon and northern California in the United States, emptying into the Pacific Ocean. By average discharge, the Klamath is the second larges ...

estuary, and

San Francisco Bay San Francisco Bay is a large tidal estuary in the U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the big cities of San Francisco, San Jose, and Oakland. San Francisco Bay drains water from a ...

. The longfin smelt have been primarily affected by import and export of water from these estuaries, resulting in high mortality rates. They have been collected from the mouth of the Russian River occasionally, and a single fish was once caught in

Monterey Bay Monterey Bay is a bay of the Pacific Ocean located on the coast of the U.S. state of California, south of the San Francisco Bay Area and its major city at the south of the bay, San Jose. San Francisco itself is further north along the coast, by a ...

. In addition, there are landlocked populations in British Columbia's

Harrison Lake Harrison Lake is the largest lake in the southern Coast Mountains of Canada, being about 250 square kilometres (95 mi²) in area. It is about 60 km (37 mi) in length and at its widest almost 9 km (5.6 mi) across. Its so ...

, and the

Lake Washington Lake Washington is a large freshwater lake adjacent to the city of Seattle. It is the largest lake in King County and the second largest natural lake in the state of Washington, after Lake Chelan. It borders the cities of Seattle on the west, ...

. In 2020 it was discovered, from annual surveys of

from 2011–2019, that a locally abundant population of longfin smelt spawns in the southernmost portion of the bay, in the marshes and sloughs capturing freshwater outflows from Coyote Creek in

Santa Clara County, California Santa Clara County, officially the County of Santa Clara, is the sixth-most populous county in the U.S. state of California, with a population of 1,936,259, as of the 2020 United States Census, 2020 census. Santa Clara County and neighboring Sa ...

. The recent conversion of salt ponds into the

tidal marsh A tidal marsh (also known as a type of "tidal wetland") is a marsh found along rivers, coasts and estuaries which floods and drains by the tidal movement of the adjacent estuary, sea or ocean. Tidal marshes are commonly zoned into lower marshes ( ...

combined with low salinity, nutrient-rich effluent recycled water from the San Jose-Santa Clara Regional Wastewater Facility may be supporting an important previously unknown source population of longfin smelt. Although once one of the most common species found in the San Francisco and Humboldt bays, even as late as the 1970s, they are now much less frequent in the smelt fishery. Given past abundance in the San Francisco Bay estuary, longfin smelt were likely historically an important forage fish, but have declined 99.9% from pre-1980's levels. In 1992 the Natural Heritage Institute petitioned to list longfin smelts as an endangered species, but the petition was denied the following year, among the reasons being given was that the decline was not observed elsewhere. The reasons for decline are not known; Peter Moyle suggests estuary outflow reduction,

entrainment Entrainment may refer to: * Air entrainment, the intentional creation of tiny air bubbles in concrete * Brainwave entrainment, the practice of entraining one's brainwaves to a desired frequency * Entrainment (biomusicology), the synchronization o ...

is connection with the pumping of water out of the Delta area, climatic variations, water pollution, and the impact of introduced species as possibilities. As of 2012, the longfin smelt has been added to the list of candidates for potential protection under the Endangered Species Act. It will be monitored annually and assessed against higher priority species. The California Department of Fish and Wildlife found only three longfin smelt in their Fall Midwater Trawl Annual Fish Abundance Summary conducted in fall of 2015. This is the lowest amount of recorded longfin smelt in the history of Fall Midwater Trawl Surveys.

References

* *

Peter B. Moyle Peter B. Moyle (born 1942 in Minnesota) is Distinguished Professor Emeritus in the Department of Wildlife, Fish and Conservation Biology and associate director of the Center for Watershed Sciences at the University of California, Davis. He has s ...

, ''Inland Fishes of California'' (University of California Press, 2002), pp. 234–239 * Damon, L. and J. DuBois, ''Memorandum: 2015 SKT Delta Smelt Index,'' California Department of Fish and Wildlife, December 18, 2015. * U.S. Fish and Wildlife Survey, ''Longfin Smelt 12 Month Finding'', Last Updated: December 19, 2015. * * Rosenfield, J. and D. Baxter, "Population Dynamics and Distribution Patterns of Longfin Smelt in the San Francisco Estuary".Transactions of the American Fisheries Society, 2007,136:6, 1577-1592 {{Taxonbar, from=Q2843922

longfin smelt The longfin smelt (''Spirinchus thaleichthys'') is a smelt (fish), smelt that is found in several estuary, estuaries and lakes along the northern Pacific coast of North America. Its most distinctive characteristic is the long pectoral fins that r ...

Western North American coastal fauna Fauna of Western Canada Fish of the Western United States

Taxa named by William Orville Ayres