Berryteuthis magister
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Berryteuthis magister |
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| ( Berry , 1913) |
Berryteuthis magister is a species of squid from the Gonatidae family. It lives in the North Pacific and occurs in the subarctic waters off Japan, Korea, Russia and North America. With a total length of up to one meter, of which a little more than half is accounted for by the arms, and weighing more than two kilograms, they are comparatively large squids.
The adult animals live in larger groups in the area of the sea floor, where they feed mainly on smaller fish and other squids, but also cannibalistically on representatives of the same species. Berryteuthis magister has a lifespan of around two years, of which around 6 months are spent on development in the egg and 18 months on further development up to sexual maturity. At the end of their life, the animals mate, with the males placing a sperm packet ( spermatophore ) in the female's coat with the help of a specially converted arm . The females lay an average of around 40,000 eggs, which are fertilized by the sperm from the spermatophore.
Berryteuthis magister is an important prey for numerous species of predatory fish, toothed whales and birds. They are also the only squids within the Gonatidae that are commercially fished by humans in a targeted manner.
features
Berryteuthis magister reaches a coat length of about 34 centimeters on average, maximum lengths of up to 43 centimeters are documented. Then there are the arms and tentacles , which can reach up to 160% of the length of the mantle and thus a length of more than 50 centimeters. The width of the jacket is usually about 34 to 37% of the length and accordingly averages about 12 to 15 centimeters. The maximum weight of the animals is 2.2 to 2.6 kilograms. The coat is big and muscular. The fins are large, rhomboid and clearly separated, they reach a length of up to 50% of the mantle length and a width of 70 to 80% of the mantle length. The tentacles and the arms are strongly built and reach a length of 120 to 160% of the length of the mantle. The widened ends of the tentacles are long and wide. These tentacle clubs have no hooks, but a large number of small, stalked suction cups that are laid out in 20 or more rows. The central suction cups are significantly larger than the outer ones.
A distinctive feature to Berryteuthis anonychus (which also remains much smaller) are large hooks, which in animals of both sexes are developed in the form of two central rows on arms I to III on both sides and in adult animals almost the entire arms with the exception of the tips take, corresponding hooks are also formed in the related genus Gonatus . The arms IV have four rows of suction cups that are applied in 60 pairs. In the male animals, a ventral arm, the Hectocotylus , is equipped with modified suction cups, which is used to transfer the sperm packet ( spermatophore ) to the female during mating . The radula has seven rows of teeth arranged lengthwise.
Ventral view
View of the mouth opening
Hooks on the arms
Extension of the tentacles with suction cups
distribution
Berryteuthis magister is widespread in the subarctic sea areas in the North Pacific, where it can be found off the coasts of Japan, Korea, Russia and North America. Its distribution area extends from the Sea of Japan and along the Kuril Islands through the Sea of Okhotsk and the Bering Sea as well as along the Aleutian Islands to the eastern North Pacific and the waters of central or southern California. It is particularly common near the bottom of the continental shelf. The most southern find information comes from the Sea of Japan off the Oki Islands or Monterey Bay on the California coast, the northernmost to the Bering Strait . From the Sea of Okhotsk southwest of Kamchatka, densities of up to 54,000 individuals per square kilometer have been determined.
Way of life
Berryteuthis magister is a species of squid that lives largely close to the ground and is mainly found in the high seas away from the coasts. The species occurs at depths of up to 1500 meters, but also occurs in the area of the sea surface. The main distribution area is in the area of the continental shelf in the mesopelagic (200 to 1000 meters depth) zone of the oceans, while in the epipelagial area (the area up to 200 meters deep) it occurs less frequently than other species of the Gonatidae of the North Pacific.
nutrition
During their pelagic phases, the young and growing squids feed primarily on various crustaceans such as luminous shrimp and krill crabs, as well as pelagic amphipods ( Hyperiidea ) and other crustaceans. Change the larger individuals on a diet of small fish and squid to, wherein in Berryteuthis magister even cannibalism occurs in all age groups and large quantities of the same species are eaten. During this feeding phase, the digestive gland (“liver”) becomes very large and reaches up to 25 or even 40% of the total wet body weight. The animals accumulate enough reserves to cover the entire energy requirement during their final ripening and spawning . During this last benthic phase (on the seabed) the feeding activity is very low and then stops completely in 92% of the mature males and 100% of the mature females.
Reproduction and development
Although Berryteuthis magister is relatively common and in larger quantities in the North Pacific, there is very little evidence of newly hatched, paralarval, animals. The paralarms occur in epipelagic zones of the high seas down to depths of around 400 meters and they have so far been documented mainly in the Gulf of Alaska . Older juveniles with a mantle length of 40 to 120 mm regularly stay near the bottom at a depth of 300 to 450 m in the Bering Sea in epi- and mesopelagic water areas. Young Berryteuthis magister migrate more frequently than related species such as Gonatopsis borealis into the lower water zones, so that even at night juvenile Berryteuthis magister are rarely found in the upper epipelagic waters. Squids in later development descend into the benthic habitat on the ocean floor, where they gather during the day. At night they spread in the ground and occasionally in the Mesopelagic zone to look for food.
Females produce egg masses up to 50 centimeters in diameter, which they presumably anchor to the sea floor with a tail-shaped appendix (direct observations of oviposition are missing). The eggs remain within the egg masses throughout embryogenesis. Finally, free-swimming paralarms with a coat length of around 3.5 millimeters hatch. With a coat length of about 7 millimeters, they develop four normal pairs of arms and a couple of longer tentacles called tentacles. Only with a mantle length of about 20 to 30 millimeters do they begin vertical migrations, whereby they rise to near the water surface at night. From a mantle length of around 70 millimeters, they revert to the benthic way of life.
Due to the large geographic distribution of Berryteuthis magister , spawning can take place regionally at different times and throughout the year. The number of sexually mature males and females increases sharply as the spawning season approaches, and the mating of the animals takes place immediately before spawning, with only mature females being mated. The penis of Berryteuthis magister is very short and does not extend beyond the edge of the coat . The spermatophores formed in the testes are transferred to the female's mantle cavity via the abdominal arm, which has been modified to form a hectocotylus , where they are attached to the mantle wall next to the openings in the fallopian tubes or to the midgut gland or the gills.
Judging by the number of spermatophores transferred, most females copulate twice, less often once or three times. In the Bering Sea, the females each produce between around 20,000 to 96,000, on average 40,000, eggs, while the males develop a total of up to 700 to 1000 spermatophores. In the Sea of Japan, where the squids are significantly smaller and produce larger eggs, the individual number is only around 4,000 eggs. Spawning takes place on the ground, presumably at a depth of 400 to 1000 meters depending on the location, and the development time until the paralarvae hatch is estimated at around 6 months.
Berryteuthis magister likely has a 2 year life cycle. The growth analyzes based on the growth rings on the statoliths and gladii suggest that the life cycle in the western Bering Sea includes 6 months of embryonic development and 18 months of post-embryonic growth. Several different seasonal age groups can exist within a region and are associated with several spawning events over the course of a year or with different origins. Since the age structure can only be deduced indirectly from the growth rings, it is very uncertain. Looking at several measurement methods together, many researchers conclude that a life span of around 13 to 14 (up to 16) months, including the embryonic phase, is two years. Statements of up to four years are considered to be implausible.
Predators
Berryteuthis magister belongs to the food spectrum of numerous predators in the North Pacific, including numerous fish, whales and other animals. Fish include cod such as the Pacific pollack and Pacific cod , Pacific salmon such as king salmon , ketal salmon , sockeye salmon and silver salmon , sea bream , black and Pacific halibut , coalfish , stonefish , bellies and numerous other species. Among the whales they are mainly used by toothed whales like Black whales , pilot whales , Dall's porpoises , the little whale or even sperm whales captured. In addition, there are the northern fur seal and various sea birds such as the thick-billed mum or the albatross . In addition, Berryteuthis magister is partially cannibalistic , so that it is also a predator for its own species.
Systematics
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Berryteuthis magister was first scientifically described in 1913 by the American zoologist Samuel Stillman Berry on the basis of two individuals from the Puget Sound , a sea bay in the northwest of the American state of Washington . He identified the animals in 1912 first as a representative of Gonatus fabricii and published this in his article "A Review of the Cephalopods of Western North America", but corrected this after he got a real G. fabricii from the Irish coast and this with his animals could compare. He now described the animals from the Puget Sound as Gonatus magister , placing them in the same genus as G. fabricii . In 1921 the Swiss zoologist Adolf Naef moved the species as a nomenclature type to the newly established genus Berryteuthis , which he named after Berry.
Berryteuthis magister was the only described species in the genus Berryteuthis until 1963 , when William G. Pearcy and Gilbert L. Voss introduced another form in the genus with Berryteuthis anonychus .
There are three subspecies within the species:
- Berryteuthis magister magister ( Berry, 1913 ), nominated form from the west coast of North America.
- Berryteuthis magister nipponensis Okutani & Kubodera, 1987 , described from the region around Hokkaido , Japan.
- Berryteuthis magister shevtsovi Katugin, 2000 , described from the Sea of Japan.
The genus Berryteuthis forms Gonatus and Gonatopsis the gonatidae family. The genera Gonatus and Berryteuthis are morphological in many characters
Threat and protection
The International Union for Conservation of Nature classifies Berryteuthis magister as not endangered ( least concern ). The classification is justified with its wide geographical distribution. Although this species is exposed to fishing pressure, it is regionally limited and the catch appears to be stable and currently sustainable . However, further research is recommended to determine the exact distribution, population dynamics, life history and ecology, and the potential threat processes affecting this species.
Importance for fishing
Due to its size and specific characteristics , Berryteuthis magister is the only species of the Gonatidae that is targeted for targeted fishing, while other species are usually only caught as bycatch . After a relatively short development period, the species collects at the bottom of the oceans, where the spawning phase also takes place, and forms larger groups there. This makes the species accessible for trawling. The meat also remains muscular and does not become gelatinous like many other species of squid. It is judged to be tasty and contains a high content of useful proteins, as a result of which Berryteuthis magister is fished as a popular edible squid throughout its range, especially in the Russian and Japanese marine areas.
Although the size of the populations of this species is unknown, some catch statistics are available from fisheries. Commercial fishing for Berryteuthis magister began in the 1960s, when the species was caught and used as by-catch, especially in the ground-level cod fishery. In the 1970s and 1980s, the fishery switched to targeted trawling and mainly took place in the northern Kuril Islands and the Bering Sea, later it was expanded into the Sea of Japan. In 1986 more than 65,000 tons of Berryteuthis magister were caught by the Russian fishery , shortly afterwards the quantities collapsed to 13,000 tons in 1986, which probably indicates a decrease in the population size in the Russian fishing areas. In the 1990s, catches remained below 20,000 tons. It is currently estimated that a fishery spanning the western Bering Sea, the northwestern Pacific and the Russian fishing areas in the Sea of Japan could produce an annual catch of 98,000 tons. The fisheries statistics of the Food and Agriculture Organization of the United Nations (FAO) reported consumption of around 49,000 tons in 2007 in 2010 and remained constant at 50,000 to 60,000 tons of fished Berryteuthis magister worldwide until 2011 .
The highest recorded catch in Russian fisheries in 2006 was 90,300 tons, while the average catch over the last decade ranged from 38,300 to 76,700 tons. Depending on the year of catch, the species thus accounts for a good 80 to over 99 percent of all Russian octopus catches. The most important fishing areas are the shelf edges near the Kuril Islands. In the western Bering Sea, less than ten percent of the catch, mostly as bycatch, was usually made. Due to the strong relief of the seabed, only limited sections can be used for trawling.
supporting documents
- ↑ a b c d e f g h i j k l m n o C.FE Roper, EM Jorgensen, ON Katugin, P. Jereb: Family Gonatidae. In P. Jereb, CFE Roper (Ed.): Cephalopods of the world. An annotated and illustrated catalog of species known to date. Volume 2. Myopsid and Oegopsid Squids. FAO Species Catalog for Fishery Purposes No. 4, vol. 2., Rome 2010; Pp. 200-222. ( Full text )
- ↑ a b c d e f Tsunemi Kubodera: Tree of Life web project: Berryteuthis magister (engl.), 2015; accessed on March 25, 2020.
- ↑ a b c d Oleg N. Katugin, Gennadyi A. Shetsov, Mikhail A. Zuev, Vasilyi D. Didenko, Vladimir V. Kulik, Noklai S. Vanin: Berryteuthis magister, Schoolmaster Gonate Squid. Chaper 1 in: Rui Rosa, Graham Pierce, Ron O'Dor (editors): Advances in Squid Biology, Ecology and Fisheries Part II - Oegopsid squids. Nova Science Publishers, 2013. ISBN 978-1-62808-333-0 .
- ^ SS Berry: A Review of the Cephalopods of Western North America. Bulletin of the Bureau of Fisheries 30, 1912; Pp. 267-336; Description on p. 308 ff. And illustrations on p. 336 ff. ( Full text )
- ↑ a b S.S. Berry: Notes on some West American cephalopods. Proceedings of the Academy of Natural Sciences of Philadelphia 65, 1913; Pp. 72-77.
- ↑ Tsunemi Kubodera, Takashi Okutani: The systematics and identification of larval cephalopods from the northern North Pacific. Research Institute of North Pacific Fisheries, Special Volume 1981; Pp. 131-159.
- ↑ Takashi Okutani, Tsunemi Kubodera: Berryteuthis magister nipponensis Okutani & Kubodera, n. Sbsp. In: Cephalopods from continental shelf and slope around Japan. Japan Fisheries Resource Conservation Association, Tokyo 1981; Pp. 132-135.
- ↑ Oleg N. Katugin: A new subspecies of the schoolmaster gonate squid, Berryteuthis magister (Cephalopoda: Gonatidae), from the Japan Sea. The Veliger 43, 2000; Pp. 82-97. ( Full text )
- ↑ a b c d Berryteuthis magister in the endangered Red List species the IUCN 2020 Posted by: I. Barratt, L. Allcock, 2014. Accessed March 26, 2020th
Web links
- Tsunemi Kubodera: Tree of Life web project: Berryteuthis magister (engl.), 2015
- Berryteuthis magister in the World Register of Marine Species
- Berryteuthis magister in the endangered Red List species the IUCN 2020 Posted by: I. Barratt, L. Allcock, 2014. Accessed March 26, 2020th
