Flathead sole
Encyclopedia
The flathead sole, Hippoglossoides elassodon, is a flatfish
of the family Pleuronectidae
. It is a demersal fish that lives on soft, silt
y or muddy bottoms at depths of up to 1050 metres (3,444.9 ft). Its native habitat is the northern Pacific
, from the seas of Japan
and Okhotsk
, across the Bering Sea
and to the coast of North America
, as far south as Point Reyes
, USA. It in length, and can weigh up to 1.56 kilograms (3.4 lb); females are typically larger than males. Lifespan is at least 27 years for females and at least 30 years for males.
and anal fins also have dusky blotches. The lateral line
curves slightly around the pectoral fin. The upper jaw is narrow in the middle and has one row of teeth.
.
s such as clam
s, worms
and brittle star
s, as well as fish
and squid
.
, Alaska pollock
, arrowtooth flounder
, Greenland turbot and Pacific halibut
.
and one off the West Coast
. Commercial fishing is conducted by trawler. Annual catches average around 17,000 tons in the Bering Sea and Aleutian Islands area; in 2008 the Gulf of Alaska catch reached its highest ever level of 3,396 tons. The discard rate
for each area is around 10%.
Flathead sole is not currently overfished
, and biomass
is estimated to be above the level required to support the maximum sustainable yield
. In the Bering Sea and Aleutian Islands area, biomass was estimated at 535,356 tons in 2008, down from a peak of almost 800,000 tons in 1997; in the Gulf of Alaska, biomass was estimated at 280,000 tons in 2007, where biomass has fluctuated around an average of 220,000 tons since 1984.
Flatfish
The flatfish are an order of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through and around the head during development...
of the family Pleuronectidae
Pleuronectidae
Righteye flounders are a family, Pleuronectidae, of flounders. They are called "righteye flounders" because most species lie on the sea bottom on their left side, with both eyes on the right side. The Paralichthyidae are the opposite, with their eyes on the left side.Their dorsal and anal fins are...
. It is a demersal fish that lives on soft, silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
y or muddy bottoms at depths of up to 1050 metres (3,444.9 ft). Its native habitat is the northern Pacific
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
, from the seas of Japan
Sea of Japan
The Sea of Japan is a marginal sea of the western Pacific Ocean, between the Asian mainland, the Japanese archipelago and Sakhalin. It is bordered by Japan, North Korea, Russia and South Korea. Like the Mediterranean Sea, it has almost no tides due to its nearly complete enclosure from the Pacific...
and Okhotsk
Sea of Okhotsk
The Sea of Okhotsk is a marginal sea of the western Pacific Ocean, lying between the Kamchatka Peninsula on the east, the Kuril Islands on the southeast, the island of Hokkaidō to the far south, the island of Sakhalin along the west, and a long stretch of eastern Siberian coast along the west and...
, across the Bering Sea
Bering Sea
The Bering Sea is a marginal sea of the Pacific Ocean. It comprises a deep water basin, which then rises through a narrow slope into the shallower water above the continental shelves....
and to the 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...
, as far south as Point Reyes
Point Reyes
Point Reyes is a prominent cape on the Pacific coast of northern California. It is located in Marin County approximately WNW of San Francisco. The term is often applied to the Point Reyes Peninsula, the region bounded by Tomales Bay on the northeast and Bolinas Lagoon on the southeast...
, USA. It in length, and can weigh up to 1.56 kilograms (3.4 lb); females are typically larger than males. Lifespan is at least 27 years for females and at least 30 years for males.
Description
The flathead sole is a right-eyed flounder with an oval-shaped body. Its upper surface is dark in colour, olive brown to reddish grey-brown, and may have dusky blotches; its underside is white with translucent areas. The dorsalDorsal fin
A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...
and anal fins also have dusky blotches. 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...
curves slightly around the pectoral fin. The upper jaw is narrow in the middle and has one row of teeth.
Role in ecosystem
The flathead sole occupies an intermediate trophic level in the food chainFood chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
.
Diet
The flathead sole's diet consists of zoobenthos invertebrateInvertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s such as clam
Clam
The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...
s, worms
Marine worm
Any worm that lives in a marine environment is considered a marine worm. Marine worms are found in several different phyla, including the Platyhelminthes, Nematoda, Annelida , Chaetognatha, Hemichordata, and Phoronida....
and brittle star
Brittle star
Brittle stars or ophiuroids are echinoderms in the class Ophiuroidea closely related to starfish. They crawl across the seafloor using their flexible arms for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to in length on the largest specimens...
s, as well as fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
and squid
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
.
Predators
The main predators of the flathead sole are the Pacific codPacific Cod
The Pacific cod, Gadus macrocephalus, is an important commercial food species. It is also known as gray cod, gray goo, gray wolf, grayest or grayfish. It has three separate dorsal fins, and the catfish-like whiskers on its lower jaw. In appearance, it is similar to the Atlantic Cod...
, Alaska pollock
Alaska pollock
Alaska pollock or walleye pollock is a North Pacific species of the cod family Gadidae. While related to the common Atlantic pollock species of the same family, the Alaska pollock is not a member of the same Pollachius genus.The Norwegian pollock , a rare fish of Norwegian waters, may actually be...
, arrowtooth flounder
Arrowtooth flounder
Arrowtooth flounder are members of the family Pleuronectidae, the right-eyed flounders. It can be caught from the Bering Sea to Santa Rosa Island, California. Spawning occurs from December through February. This species of flounder can live up to 25 years. If not properly handled, the flesh of...
, Greenland turbot and Pacific halibut
Pacific halibut
The Pacific halibut is found on the continental shelf of the North Pacific Ocean and Bering sea. They are demersal, living on or near the bottom. The halibut is among the largest teleost fish in the world. Halibut are strong swimmers and are able to migrate long distances...
.
Commercial fishing
The USA lands the majority of the world's catch of flathead sole and manages three fisheries - one in the Bering Sea and Aleutian Islands, one in the Gulf of AlaskaGulf of Alaska
The Gulf of Alaska is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the east, where Glacier Bay and the Inside Passage are found.The entire shoreline of the Gulf is...
and one off the West Coast
West Coast of the United States
West Coast or Pacific Coast are terms for the westernmost coastal states of the United States. The term most often refers to the states of California, Oregon, and Washington. Although not part of the contiguous United States, Alaska and Hawaii do border the Pacific Ocean but can't be included in...
. Commercial fishing is conducted by trawler. Annual catches average around 17,000 tons in the Bering Sea and Aleutian Islands area; in 2008 the Gulf of Alaska catch reached its highest ever level of 3,396 tons. The discard rate
Discards
Discards are the portion of a catch of fish which is not retained on board during commercial fishing operations and is returned, often dead or dying, to the sea...
for each area is around 10%.
Flathead sole is not currently overfished
Overfishing
Overfishing occurs when fishing activities reduce fish stocks below an acceptable level. This can occur in any body of water from a pond to the oceans....
, and biomass
Biomass (ecology)
Biomass, in ecology, is the mass of living biological organisms in a given area or ecosystem at a given time. Biomass can refer to species biomass, which is the mass of one or more species, or to community biomass, which is the mass of all species in the community. It can include microorganisms,...
is estimated to be above the level required to support the maximum sustainable yield
Maximum sustainable yield
In population ecology and economics, maximum sustainable yield or MSY is, theoretically, the largest yield that can be taken from a species' stock over an indefinite period...
. In the Bering Sea and Aleutian Islands area, biomass was estimated at 535,356 tons in 2008, down from a peak of almost 800,000 tons in 1997; in the Gulf of Alaska, biomass was estimated at 280,000 tons in 2007, where biomass has fluctuated around an average of 220,000 tons since 1984.