Monochrome tuna
| Monochrome tuna | ||||||||||||
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Single-color tuna ( Gymnosarda unicolor ) |
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| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Gymnosarda | ||||||||||||
| Gill , 1862 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Gymnosarda unicolor | ||||||||||||
| ( Rüppell , 1836) |
The dogtooth tuna ( Gymnosarda unicolor ) or dog tooth tuna is a 1.5 meter long and 80 kilogram predatory fish, which in small flocks or individually steep outer reefs in Riffkanälen and deep lakes, to shoal fish such as fusiliers or Carangidae and cephalopods hunts . It is the only species in the genus Gymnosarda .
features
The monochrome tuna has a slim, torpedo-shaped shape that is slightly flattened on the sides. The average body length of the adult animals is around 1.50 meters with a body weight of around 80 kilograms. The largest individual to date was 2.04 meters long and weighed 131 kilograms and was caught off the coast of Korea in 1982 ; a maximum length of 2.48 meters has been documented for another animal. Populations with significantly slimmer specimens occur in the Ogasawara Islands (Japan) with an average length of 1.0 to 1.5 meters and a weight between 20 and 30 kilograms. In the area of the Fiji Islands, the animals are only about 0.65 to 1.0 meters long and weigh 5 to 15 kilograms.
The body color of the back and the upper flank area is shiny blue-black, the lower flank part and the belly are silvery. The body has no markings or spots. It is unscaled after the chest area except for the area of the lateral line, the base of the dorsal fin and the tail stalk. The lateral line organ is strongly wavy. The caudal peduncle is long and narrow and has a distinct side keel as well as two pair of smaller keels on both sides of the tail root.
The mouth is relatively large and extends to about half of the eyes. In the upper jaw the fish has 14 to 31 and in the lower jaw 10 to 24 large, conically shaped teeth. There are also two tooth fields on the top of the tongue. The head width ( interorbital distance) is about 40% of the head length.
The two dorsal fins are close together. The first dorsal fin is dark and consists of 13 to 15 fin rays. The outer tips of the second dorsal fin and the anal fin are gray-white, followed by 6 to 7 fin-like structures (finlets) along the tail style. The paired pectoral fins consist of 25 to 28 rays. The pelvic process (interpelvic process) is unpaired and long. The tail is sickle-shaped and corresponds to that of other tuna relatives.
The swim bladder of these animals is relatively large. The large spleen lies on the right side in the front area of the body cavity. The liver has elongated right and left lobes while the middle lobe is only short. The spine consists of 19 back and 19 tail vertebrae.
distribution and habitat
The monochrome tuna lives in the tropical areas of the Indo-Pacific from the Red Sea and the East African coast and Madagascar to Japan , the Philippines , New Guinea , Australia and Samoa .
It is a surface fish that is found mainly in the area of coral reefs . The preferred water temperature is 20 to 28 ° C.
Way of life
Monochrome tuna mostly live individually or in small groups (schools). They hunt for smaller schooling fish and squid. Its prey consists mainly of species of the genera Decapterus , Caesio , Naso , Cirrhilabrus and Pterocaesio . Very little is known about their reproductive biology; they reach sexual maturity from a body length of around 65 centimeters. In the area around Fiji, the spawning season is in the summer months.
Threat and protection
The single-color tuna is not fished specifically and therefore does not play a central role as food fish. As a rule, the catch is carried out unspecifically with lines or nets, especially in the Philippines, near Port Blair , the Andaman Islands , Japan, the Fiji Islands and the reefs off the Australian coast. It is not listed in the IUCN's Red List of Endangered Species .
supporting documents
Evidence cited
- ^ After ITIS and Collette, Nauen: Scombrids of the world. 1983, pp. 40-42.
- ↑ a b c d after Collette, Nauen: Scombrids of the world. 1983, pp. 40-42.
- ↑ a b to fishbase
literature
- Bruce B. Collette, Cornelia E. Nauen: Scombrids of the world. An annotated and illustrated catalog of tunas, mackerels, bonitos and related species known to date (= FAO Species Catalog. Vol. 2 = FAO Fisheries Synopsis. No. 125, Vol. 2). United Nations Development Program et al., Rome 1983, ISBN 92-5-101381-0 , pp. 40-42 ( full edition ).
Web links
- Monochrome tuna on Fishbase.org (English)
- Photos at Fishbase
- Gymnosarda unicolor inthe IUCN 2013 Red List of Threatened Species . Posted by: Collette, B., Di Natale, A., Fox, W., Juan Jorda, M. & Nelson, R., 2009. Retrieved February 9, 2014.