Garter fish
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Garter fish ( Lepidopus caudatus ) |
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| Lepidopus caudatus | ||||||||||||
| ( Euphrases , 1788) |
The garter fish or scabbard fish ( Lepidopus caudatus ) is a fish of the genus Lepidopus from the hairtail family (Trichiuridae) that lives above the seabed and in open water ( benthopelagial ). The distribution area of the predatory fish, which is up to two meters long, extends from the north and south of the Atlantic across the south of the Indian Ocean to the south of the Pacific . The garter fish is of commercial interest for fishing in many countries.
General
Lepidopus caudatus was first described in 1788 by the Swedish naturalist Bengt Anders Euphrasén under the name Trichiurus caudatus . Other synonyms are Lepidopus argenteus (Bonnaterre, 1788), Lepidopus gouanianus (Lacepède, 1800), Lepidopus lex (Phillipps, 1932), Lepidopus peronii (Risso, 1810), Lepidopus xantusi (Goode & Bean, 1896), Scarcinesque , Argyrea ( Rafcinesque 1810), Trichiurus ensiformis (Vandelli, 1797), Trichiurus gladius (Holten, 1802), Vandellius lusitanicus (Shaw, 1803) and Ziphotheca tetradens (Montagu, 1811).
features
Like most fish, L. caudatus has a bilaterally symmetrical body. This is laterally flattened and very strongly elongated like a ribbon. The most important identifying characteristics are listed in the FAO Species Catalog of the United Nations . These are described below.
The fish's dorsal fin extends from the head to the caudal fin. It consists of 98 to 110 soft rays , which are connected by a membranous membrane. Behind the pair of pectoral fins are the only rudimentary pelvic fins. The anal fin consists of 59 to 66, partially separated, thorn-like soft rays, of which only the 15 to 24 further back are connected by a membranous membrane. The tail fin, which is relatively small in relation to the body size, is clearly set off and forked.
The length of the head corresponds approximately to 12% of the total body length. The eyes of the garter fish are, like many other fish species that occur at depths of 200 to 1000 meters ( mesopelagial ), relatively large. The fish's mouth is inclined upwards and is also relatively large in relation to the size of the head. The lower jaw is slightly longer than the upper jaw. The mouth is toothed. In addition, the garter fish has clearly pronounced palatal teeth.
The entire body is bare and of a characteristic, silvery and easily peeling color. In individuals that come from populations of the North Atlantic or the Mediterranean, the dorsal fin is colored black-gray throughout. Individuals from the populations of the southern hemisphere have a black spot in the front of the caudal fin.
The largest known individuals are over two meters long and weigh about eight kilograms. However, it is believed that there are even larger specimens.
distribution and habitat
The garter fish is widespread in the entire east Atlantic, the Mediterranean , the southern Indian Ocean, as well as in the Southeast Pacific off the coasts of Australia and New Zealand . It was also found on the deep sea mountains of the Atlantic Ridge, where it plays an important role in the local ecosystem due to its high abundance.
In general, it is a benthopelagial species that mostly occurs over the edge of the continental shelf . The garter fish prefers to stay above muddy or sandy sediment bottoms. L. caudatus can often be found in mesopelagial open water.
The depths inhabited by the fish can vary between populations, mainly due to the different conditions of the individual habitats. Typically during the day it stays in waters between 250 and 750 m depth. At night it migrates to shallower depths of up to 50 m. In rare cases, the garter fish can also be found in the immediate vicinity of the coast. In addition, a variation in depth over the course of the seasons could also be determined, with the individuals staying in deeper waters during the summer months than in winter. A connection between the size of the individuals and the populated depth could also be established. Larger and heavier individuals stay at a shallower depth than smaller and lighter individuals. This size-dependent distribution in the vertical could be based on migration behavior, which may begin in the course of life.
Diet and Predators
The garter fish is a school of predatory fish. The most important group of prey organisms are other fish species. The garter fish hunts mainly at night and in the early morning hours. The range of prey is broad and can vary over the course of the year.
Basically, the food is of L. caudatus of crustaceans, such as euphausiid ( Euphausiacea ) and decapods (Decapoda), small cuttlefish ( cephalopods ) and other smaller fish, such as Lampanyctodes hectoris or Gadiculus argenteus , together. In some cases smaller conspecifics are also eaten. In the range of prey for young animals, crustaceans are particularly important. Larger individuals, on the other hand, mainly feed on smaller fish. They show a more pelagial hunting behavior, while smaller individuals tend to look for their food near the bottom.
The range of prey of the garter fish clearly reflects its mesopelagial habitat. The size of the prey caught by L. caudatus is proportional to its own body size. Nevertheless, the ratio of body size to the size of the prey organisms of L. caudatus is unusually small compared to other predatory fish.
Typical predators of L. caudatus are other predators, some representatives of the squill gill (Elasmobranchii) and large cephalopods .
Reproduction
In L. caudatus is a dioecious species. The pups reach an age of 1.5 to 2 years for the first time sexual maturity. Both sexes can reproduce throughout the year. The reproductive behavior of the garter fish is particularly pronounced in the period between spring and autumn.
These seasonal differences in the reproduction rate of L. caudatus are based on an only partial synchronicity of the reproductive cycles. The reproductive cycle of females is divided into three phases, the pre-productive, the reproductive and the post-reproductive phase. After reproducing, the females enter a post-reproductive phase during which no reproduction takes place. With the transition into the pre-productive phase, the oocytes begin to mature again until they reach sexual maturity. The reproduction can take place several times during the extended spawning season.
The garter fish spawns at a depth of less than 50 m, above the edge of the continental shelf or in mesopelagic open water.
development
Both the eggs and the larval stages of the garter fish are planktonic. The mean diameter of the eggs is 1.7 mm. About six days after fertilization, the slightly pink eggs hatch into a 5 mm large yolk sac larvae. This young larva has a thorn-shaped process located dorsally behind the head. The eyes are not fully developed at this point. The somewhat older pre-juveniles already resemble the juveniles in their body shape, but do not yet have the silver coloration characteristic of L. caudatus . The juveniles already correspond in their appearance to the adult individuals. The subadult individuals gain height and weight fastest in the first 2-4 years of life. Shortly after reaching sexual maturity, height growth slows down. Basically, the males gain size and weight a little faster than the females and reach sexual maturity earlier. The garter fish can live up to 13 years.
Fisheries and threats
Although targeted fishing for L. caudatus is rarely practiced, the garter fish is of economic importance in many countries. In many cases the garter fish is bycatch. However, L. caudatus has also been specifically fished in the north-western Mediterranean since the mid-1980s. The garter fish is typically caught from ships using bottom trawls , gill nets or longlines . Modified longlines are used for targeted fishing for L. caudatus , the rear end of which is reinforced with metal. The catches that can be achieved with the help of longlines are significantly greater in summer than in winter. Such a seasonal rhythm cannot be seen for the catches made with bottom trawls. Larger individuals are usually caught with the help of longlines than with trawls or gill nets.
The global catches of the garter fish showed a steady increase up to the year 1993 up to an annual reported total of 27,000 tons. Since then, the officially known catches have dropped to a value of 9,000 tons in 2010. According to Iwamoto (2015), the largest country-specific catches per year come from Portugal (2966 t) and New Zealand (2638 t).
Due to the insufficient data, only a vague statement can be made about the actual threat status of the species. The garter fish is therefore listed on the " IUCN List of Threatened Species" as "Data Deficient".
Cryptic kind
Comparative studies of L. caudatus populations from the North Atlantic and the waters around New Zealand showed a high genetic divergence between these populations. Through DNA barcoding of mitochondrial cytochrome c oxidase (COX) was found a genetic difference of 2.75%. This north-south differentiation is 6 times higher than the genetic variance within the respective examined populations.
This result suggests that L. caudatus is a cryptic species . The clear difference in coloration of the dorsal fin, as well as the differences in size and weight between the populations of the different hemispheres, support the assumption that there are in fact two different species. However, this controversy has not yet been finally resolved and further taxonomic research is required.
Individual evidence
- ↑ Lepidopus caudatus in the Catalog of Fishes (English)
- ↑ a b c d e f g Lepidopus caudatus in the Red List of Threatened Species of the IUCN 2016-3. Posted by: T. Iwamoto, 2013. Retrieved April 20, 2017.
- ↑ a b c d e Nakamura, I. and N. Parin: FAO species catalog. v. 15: Snake mackerels and cutlassfishes of the world (Families Gempylidae and Trichiuridae). An annotated and illustrated catalog of the Snake Mackerels, Snoeks, Escolars, Gemfishes, Sackfishes, Domine, Oilfish, Cutlassfishes, Scabbardfishes, Hairtails and Frostfishes known to date, FAO. 1993.
- ↑ a b c d e Klimpel, S., et al .: "Diet and metazoan parasites of silver scabbard fish Lepidopus caudatus from the Great Meteor Seamount (North Atlantic)." Marine Ecology Progress Series 315: 249-257. 2006.
- ↑ a b c d e f g h i j k Demestre, M., et al .: "Life history and fishery of Lepidopus caudatus (Pisces: Trichiuridae) in the Catalan Sea (Northwestern Mediterranean)." 1993.
- ↑ Tsagarakis, K., et al .: "Discards of the purse seine fishery targeting small pelagic fish in the eastern Mediterranean Sea." Scientia Marina 76 (3): 561-572. 2012.
- ↑ a b c d Tuset, V., et al .: "Reproductive pattern and growth in Lepidopus caudatus (Osteichthyes, Trichiuridae) from the Canary islands (Eastern-Central Atlantic). Electron." J. Ichthyol 1: 26-37. 2006.
- ↑ a b c d e f Robertson, D .: "Spawning of the frostfish, Lepidopus caudatus (Pisces: Trichiuridae), in New Zealand waters." New Zealand Journal of Marine and Freshwater Research 14 (2): 129-136. 1980.
- ↑ Uiblein, F., et al .: "Diversity, abundance and depth distribution of demersal deep-water fishes off Lanzarote and Fuerteventura, Canary Islands." Journal of Fish Biology 49 (see A): 75-90. 1996.
- ↑ a b Blaber, S. and C. Bulman: "Diets of fishes of the upper continental slope of eastern Tasmania: content, calorific values, dietary overlap and trophic relationships." Marine Biology 95 (3): 345-356. 1987.
- ↑ Rodríguez-Cabello, C., et al .: "The role of silvery pout (Gadiculus argenteus) as forage prey in the Galician and Cantabrian Sea ecosystem (NE Atlantic) in the last two decades." Journal of Experimental Marine Biology and Ecology 461: 193-200. 2014.
- ↑ D'onghia, G., et al .: "Biology of silver scabbard fish, Lepidopus caudatus (Trichiuridae), from the Ionian Sea (eastern-central Mediterranean)." Cybium 24 (3): 249-262. 2000.
- ↑ a b c Ward, RD, et al .: "DNA barcoding of shared fish species from the North Atlantic and Australasia: minimal divergence for most taxa, but Zeus faber and Lepidopus caudatus each probably constitute two species." Aquatic Biology 3 (1): 71-78. 2008.
Web links
- Lepidopus caudatus on Fishbase.org (English)