|
|
The Chilean Sea Bass fish identification, Patagonian Toothfish habitats, characteristics, Fishing methods
Chilean Sea Bass, The Patagonian Toothfish is a large fish found in the cold, temperate waters (from 50 to 3850 m depth) of the Southern Atlantic, Southern Pacific, Indian, and Southern Oceans on seamounts and continental shelves around most sub-Antarctic islands. A close relative, the Antarctic toothfish, is found farther south, around the edges of the Antarctic shelf. The average weight of species is 9–10 kg (20 lbs) with large adults occasionally exceeding 200 kg (440 lbs). They are thought to live to fifty years, reaching a length of 2.3 m (8 feet). Patagonian toothfish feed largely on squid, fish and prawns and, in turn, constitute a large part of the diets of sperm whales, Southern Elephant Seals and colossal squid.
|
The Patagonian toothfish, Dissostichus eleginoides, Family Nototheniidae (cod ice fishes), also known as Chilean Sea Bass, Toothfish, Antarctic cod, Black hake, Antarctic blenny, Patagonian blenny, Icefish, is a fish found in the cold, temperate waters (between depths of 45 to 3850 m) of the Southern Atlantic, Southern Pacific, Indian, and Southern Oceans on seamounts and continental shelves around most sub-Antarctic islands, Southern Chile, Argentina, Falkland Islands, Shag Rocks, and South Georgia.
|
Description
Chilean sea bass (Dissostichus eleginoides), a large, vaguely cod-shaped fish found in cold, deep waters of the southern hemisphere, has been one of the most phenomenally successful introductions of a fish into the North
Patagonian toothfish or Chilean sea bass is an ugly, mean-looking fish with bulging eyes and a protruding jaw that was studded with teeth so pointy they looked as if they had been honed by a pencil sharpener. Their teeth are very sharp; they are the largest predatory fishes in the midwaters of the Antarctic Ocean.
|
Dorsal fin has 8-10 spines and 28 to 30 soft rays.
Anal fin has 0 spine and 28-30 soft rays.
verterbrae 53-54.
Large lateral-line scales 88-104 (upper), 61-77 (lower).
Maximum weigh is up to 440 lbs while an averages 20 pounds.
Maximum length 7 foot.
Live for up to 50 years.
|
|
Thought to descend from deepwater benthic fishes that lacked swim bladders, toothfishes have evolved to re-colonize the water column. They have unusual adaptations to achieve neutral buoyancy, including lightly mineralized bones and abundant lipids in their flesh. The toothfishes are heavily muscled with white, “slow-twitch” muscle tissue used for short bursts of speed.
It is a large fish up to 6 feet long and lives for up to 50 years. Patagonian toothfish may attain a maximum weight of approximately 440 lbs and a maximum length of approximately 7 ft. The average weight of a commercially caught toothfish is about 20 lbs.
Two closely related species known as the Patagonian toothfish and the Antarctic toothfish live in the remote Southern Ocean. Toothfishes are valued for their firm white, oil-rich flesh. While both species are marketed as Chilean sea bass, about 95% of these are Patagonian toothfish, only 5% being Antarctic toothfish.
The Antarctic Toothfish, which tends to inhabit colder and more southerly waters than Patagonian toothfish - typically south of 65 degrees latitude and sometimes under pack ice while the Patagonian occurs mostly in latitudes between 40° and 60 °south. This species also possesses an anti-freeze like component in its circulatory system which enables it to survive near freezing conditions.
Habitats
These fish inhabit the deep waters from 950 to 11,000 or more feet (300 to 3500 meters), on the seamounts and continental shelves around sub-Antarctic islands. Patagonian Toothfish inhabit deep-sea continental shelf slopes of the southern oceans, Antarctica, and the small islands dotting this oceanic region. Toothfish are bottom dwelling, but move off the bottom on occasion to feed. They are found primarily in easterly banks and appear to thrive best near land. Consequently, the fishing grounds are concentrated on continental shelves around the islands in the region.
The Patagonian toothfish is an ambush, lay-in-wait predator, as evidenced by the firm white flesh of its filets which are typical of a fish whose metabolism is geared for short bursts of energy, as opposed to the deep red muscle tissue found in species that require sustained swimming abilities like tunas or billfishes. At 4-6 inches (12-15 cm) total length, semi-pelagic juveniles become demersal at 490 - 1300 ft (150-400 m) depth. Young, immature fish are found in shallower waters on the continental shelf at 500 m but as they mature they migrate into deeper waters up to 3,000 m in depth. Adults migrate to deeper habitats at depths greater than 3,280 feet.
Patagonian toothfish feed mainly on squid, octopods, fish, crustaceans, amphipods, shrimps, krill, and other bony fishes including other toothfish. Young toothfish feed on krill and shift to fish, shrimp and cephalopods by the time they reach adulthood. They are preyed upon by sperm whales, Southern elephant seals, colossal squid and Antarctic seals at Heard Island, Australia.
Spawning
Patagonian toothfish reach sexual maturity at 9-12 years of age and about 15 to 24 inches (90-100 cm) in length, 80 cm for males and 100 cm for females. In the Atlantic sector of the southern ocean, Patagonian toothfish spawn over the continental slope from June to September, in water 2200-4400 meters deep. Patagonian toothfish like most Antarctic fishes have low fecundity and large egg size, indicating a relatively large maternal investment in each egg.
Individual mature females contained between 48,000 and 500,000 eggs; larger females produce significantly more eggs per gram of body weight. Their eggs float in the midwater about 500 meters below the surface. Eggs are few and both eggs and larvae are large, approximately the size of peppercorns. Eggs are considered to be pelagic and have been found occasionally within the upper 50 m of the water column. The larvae hatch from these pelagic eggs after approximately 3 months. Larvae first feed on krill and gradually shift to fishes as they grow. The diet of adults consists of fishes and an Antarctic bay shrimp. Like many other deepwater fishes, Toothfish are slow-growing, they gain the most of their size in their first decade and grow more slowly after that.
Present toothfish populations are estimated to possess a minimum population doubling time 4.5 - 14 years, which is exceptionally long when compared to the population doubling time of many commercially and recreationally harvested fish stocks. The long life span and late sexual maturity of the Patagonian toothfish make it highly vulnerable to overfishing.
The Antarctic toothfish has very similar biological characteristics, but is thought to grow a bit slower than Patagonian toothfish, and has a smaller maximum length (around 1.8 meters). In at least the Antarctic toothfish, eggs take two years to mature inside the female before being released and fertilized. Fish require 8-10 years to reach sexual maturity at a length of 90-100cm, and live at least 40 years. Toothfish are inherently vulnerable to fishing because of their basic biology and because they reach marketable size before sexual maturity.
Fishing
Patagonian Toothfish is one of the tastiest fish available on the market, well-known for its firm white flesh, even texture and the abundance of Omega-3 oils in the meat. It is sold under the trade name of Chilean Sea Bass in the USA, Merluza Negra or Bacalao or Bacalao de profundidad in Chile, Argentina and Uruguay, Austromerluza negra (Spain), Légine australe (France), and Ookuchi or Mero in Japan. A close relative, the Antarctic Toothfish is found further south around the edges of the Antarctic shelf.
Commercial fisheries catch these fish by trawling, and the setting of longlines. Toothfish are mainly taken by bottom longlines which involves bycatch of seabirds, most notably the internationally endangered wandering albatross and gray-headed albatross.
|
|
|
