Longfin smelt
Encyclopedia
The longfin smelt, Spirinchus thaleichthys, is a smelt that is found in several estuaries
and lakes along the northern Pacific coast of North America
.
Its most distinctive characteristic is the long pectoral fins that reach nearly to the base of the pelvic fins, 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 set of very small teeth. The lateral line
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
, Neomysis mercedis, and species of Acanthomysis
, but they will also eat copepod
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
, Phoca vitulina, in the Columbia River
.
Their primary habitat is the open water of estuaries, where they can be found in both the seawater 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
in Alaska
, also in Skagit Bay
, Grays Harbor, Willapa Bay
, lower Columbia River, Yaquina Bay
, Coos Bay
, Humboldt Bay, the Eel River
estuary, Klamath River
estuary, and San Francisco Bay
. They have been collected from the mouth of the Russian River
occasionally, and a single fish was once caught in Monterey Bay
. In addition, there are landlocked populations in British Columbia's Harrison Lake
, and the Lake Washington
.
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. 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; Moyle suggests estuary outflow reduction, entrainment
is connection with the pumping of water out of the Delta area, climatic variations, water pollution, and the impact of introduced species as possibilities.
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
and lakes along the northern Pacific coast of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
.
Its most distinctive characteristic is the long pectoral fins that reach nearly to the base of the pelvic fins, 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 set of very small teeth. The lateral line
Lateral line
The lateral line is a sense organ in aquatic organisms , used to detect movement and vibration in the surrounding water. Lateral lines are usually visible as faint lines running lengthwise down each side, from the vicinity of the gill covers to the base of the tail...
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
Mysidacea
Mysida is a group of small, shrimp-like crustaceans, an order in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch, or marsupium, in females. Mysids are mostly found in marine waters throughout the world, but are also important in...
, Neomysis mercedis, and species of Acanthomysis
Acanthomysis
Acanthomysis is a genus of mysids, containing 28 species.*Acanthomysis anomala Pillai, 1961*Acanthomysis bispinosa Bacescu, 1979*Acanthomysis borealis Banner, 1954*Acanthomysis bowmani Modlin & Orsi, 1997...
, but they will also eat copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
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
Harbor Seal
The harbor seal , also known as the common seal, is a true seal found along temperate and Arctic marine coastlines of the Northern Hemisphere...
, Phoca vitulina, in the Columbia River
Columbia River
The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...
.
Their primary habitat is the open water of estuaries, where they can be found in both the seawater 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
Prince William Sound is a sound off 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 Trans-Alaska Pipeline System...
in Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
, also in Skagit Bay
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 Passage and Possession Sound...
, Grays Harbor, Willapa Bay
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 water surface Willapa Bay is the second largest estuary on the United States Pacific coast...
, lower Columbia River, Yaquina Bay
Yaquina Bay
Yaquina Bay is a small bay partially within Newport, Oregon, United States, located where the Yaquina River flows into the Pacific Ocean. It is traversed by the Yaquina Bay Bridge. The bay's area is about 8 km² .-See also:...
, Coos Bay
Coos Bay
Coos Bay is an S-shaped inlet where the Coos River enters the Pacific Ocean, approximately 10 miles long and two miles wide, on the Pacific Ocean coast of southwestern Oregon in the United States. The estuary is situated south of the Salmon River. The city of Coos Bay, once named Marshfield, was...
, Humboldt Bay, the Eel River
Eel River (California)
The Eel River is a major river system of the northern Pacific coast of the U.S. state of California. Approximately 200 miles long, it drains a rugged area in the California Coast Ranges between the Sacramento Valley and the ocean. For most of its course, the river flows northwest, parallel to the...
estuary, Klamath River
Klamath River
The Klamath River is an American river that flows southwest through Oregon and northern California, cutting through the Cascade Range to empty into the Pacific Ocean. The river drains an extensive watershed of almost that stretches from the high desert country of the Great Basin to the temperate...
estuary, and San Francisco Bay
San Francisco Bay
San Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...
. They have been collected from the mouth of the Russian River
Russian River (California)
The Russian River, a southward-flowing river, drains of Sonoma and Mendocino counties in Northern California. With an annual average discharge of approximately , it is the second largest river flowing through the nine county Greater San Francisco Bay Area with a mainstem 110 miles ...
occasionally, and a single fish was once caught in Monterey Bay
Monterey Bay
Monterey Bay is a bay of the Pacific Ocean, along the central coast of California. The bay is south of San Francisco and San Jose, between the cities of Santa Cruz and Monterey....
. In addition, there are landlocked populations in British Columbia's Harrison Lake
Harrison Lake
Harrison Lake is the largest lake in the southern Coast Mountains of Canada, being about 250 square kilometres in area. It is about 60 km in length and at its widest almost 9 km across. Its southern end, at the resort community of Harrison Hot Springs, is c. 95 km east of...
, and the Lake Washington
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 in the state of Washington, after Lake Chelan. It is bordered by the cities of Seattle on the west, Bellevue and Kirkland on the east, Renton on the south and...
.
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. 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; Moyle suggests estuary outflow reduction, entrainment
Entrainment (physical geography)
In physical geography, entrainment is the process by which surface sediment is incorporated into a fluid flow as part of the operation of erosion....
is connection with the pumping of water out of the Delta area, climatic variations, water pollution, and the impact of introduced species as possibilities.