Common fiddle ray
| Common fiddle ray | ||||||||||||
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Common fiddle ray ( Rhinobatos rhinobatos ) |
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| Rhinobatos rhinobatos | ||||||||||||
| ( Linnaeus , 1758) |
The common fiddle ray ( Rhinobatos rhinobatos ), also known as the common fiddle ray or common guitar fish, is a fish from the genus Rhinobatos and native to the eastern Atlantic . The species is classified as critically endangered by the IUCN .
features
The shape of the common fiddle ray is reminiscent of sharks . Its uniformly khaki-brown body is elongated and tubular with fins on the trunk and a massive tail that is a continuation of the body. The tail has two large, widely spaced dorsal fins and ends in an oval caudal fin; this is similar to most sharks. A breast disk is formed on his head from his pectoral and pelvic fins, which in turn is similar to rays. Its underside is white and its snout is elongated and has rostral ridges that run towards the snout and, in contrast to Rhinobatos cemiculus, are further separated. It has small thorns around the edges of the eye sockets, on the shoulders and starting from the head to the tail in the middle of its back. This ray has molar-shaped teeth that are intended for chopping and grinding its prey. The maximum body length ever reported was 140 centimeters for a male and 160 centimeters for a female individual. Usually these rays reach a body length of 80 cm. Males reach sexual maturity at 75 and females at 85 centimeters.
distribution
The common guitar fish occurs in the eastern Atlantic from the Bay of Biscay to Angola . It is also found on the coasts of the Mediterranean (primarily in the southern and eastern regions), particularly in the Gulf of Gabès and on the east coast of Tunisia .
behavior
Rhinobatos rhinobatos lives close to the ground above sandy or muddy soils; its color makes it the ideal camouflage for such an environment. It usually resides in shallow water up to a depth of 180 meters. It swims slowly along the seabed and partly buries itself under sand and ambushes its victims with its camouflage and presses them with its long snout to the ground, then sucks them in and eats them. Young animals feed mainly on crustaceans, adolescent animals prey on crustaceans such as prawns, crabs, mantis shrimp and North Sea shrimp as well as small fish. These rays are harmless to humans. Due to its large geographic range, the common guitar fish shares its habitat with larger predatory fish that hunt it.
Reproduction
Mating occurs during the summer, followed by a nine-month gestation period. The embryo grows in the form of aplacental viviparia ; the embryos first feed on the yolk of a yolk sac in the mother's body and then receive nourishment from the mother. Approx. 4 to 10 young animals are born per litter, which are approximately 30 cm in length. These rays give birth between once and twice a year.
Hazard and protection
Although the range of this ray is very large, it is exposed to fishing almost everywhere. Its near-shore habitat makes it an easy target and is often caught as bycatch by trawls that fish primarily for shrimp, as well as bottom trawls and gill nets . It is processed further and its meat is exported salted or dried. Its caudal fins are exported to the Asian fin market.
Little is known about the life cycle and the habitat and it is not possible to precisely estimate the consequences of human activity on one's way of life. It is assumed that the habitat for young animals is particularly influenced by humans and causes a deterioration in the living situation. Little is known about the population sizes of the common guitar fish.
Therefore, this species is classified as critically endangered based on past and suspected future declines . The status of this species should be further monitored, currently this species is not subject to any conservation or management measures.
Situation in the Mediterranean
Other rays of the same genus have declined sharply and it is therefore assumed that the common guitar fish also declined sharply in the population. In the northern Mediterranean, for example, this ray was often fished as bycatch and in the Balearic Islands this species was seen as a typical seabed inhabitant, which indicates a large number of these animals. In the late 19th century this fish was still a daily presence at the fish market in Palermo , but today it is no longer found in fishermen's nets and has apparently been exterminated in these regions. It is still caught in the southern Mediterranean, the problem in this region is that most of the specimens that are caught are still juveniles and have not yet reached sexual maturity. This inevitably affects the existence of future generations. In view of the evidence of regional extinction in the northern Mediterranean and the sustained heavy catches of fish throughout the habitat of these species, including along the West African coast, there is reason to suspect that this species will suffer declines.
The Barcelona Convention assesses the status of the Rhinobatos species as endangered and assesses their environment as a risk to them.
Situation in the East Atlantic
In this area, rhinobatids are commonly caught as by-catch from crab fisheries that operate in shallow coastal waters. Dried specimens are exported to Ghana .
Catches have fallen dramatically in Senegal. The peak was reached in 1997 with 4,200 tons, since then the catches have gradually decreased to an estimated 820 tons in 2005.
In Guinea-Bissau , this species is a main target for shark trapping, gill nets are used to catch the animals. At the beginning of the 2000s, the size of one of the meshes in the gill net was between 230 and 280 millimeters, today it is 160 to 180 millimeters. This change causes smaller fish to be caught as well.
According to reports, the fiddler ray is often caught in Sierra Leone as by-catch by the shrimp trawling fishery that operates in shallow coastal waters from 14 to 26 meters. The catch rate of a recent program shows a bycatch rate of over one specimen per two hours of fishing. A national action plan to conserve these animals has been proposed, but there are no species-specific rules for catching rays and sharks.
In Mauritania it is forbidden to fish this ray in the Banc d'Arguin National Park .
Recommended actions
Mediterranean Sea
The IUCN recommends the implementation of management plans on an international as well as national level, such as the FAO's international action plan for the protection of sharks. In addition, the fisheries in these regions should be monitored better and the catch quotas of the individual species should be better recorded. In addition, coastal habitats should be better investigated and, in particular, developments should be assessed with regard to the use of trawling.
Eastern Atlantic
In this region, a targeted seasonal ban on fishing for this species and a license for targeted and non-targeted fishing of sharks are recommended. In addition, one should control the shark fin market.
supporting documents
- ↑ Common guitar ray (common fiddle ray). Zoo animal list, accessed December 15, 2017 .
- ↑ a b c d Rhinobatos rhinobatos in the endangered species Red List of IUCN 2017-3. Posted by: Notarbartolo di Sciara, G., Bradai, MN, Morey, G., Marshall, AD, Compagno, LJV, Mouni, A., Hicham, M., Bucal, D., Dulvy, N., Heenan, A . & Rui Coelho., 2007-03-01.
- ↑ Common fiddle ray on Fishbase.org (English)
- ↑ David A. Ebert: DEEP-SEA CARTILAGINOUS FISHES OF THE INDIAN OCEAN Volume 2 Batoids and Chimaeras ; Food and agriculture organization of the united nations, Rome 2014, ISBN 978-92-5-108453-3 ( // PDF ). Pp. 295-297.
- ↑ a b c d e Cathleen Bester: Common Guitarfish. Florida Museum of Natural History, accessed December 8, 2017 .
