Narrowfin Smooth Shark
| Narrowfin Smooth Shark | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Narrowfin smooth shark ( Mustelus norrisi ) |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Mustelus norrisi | ||||||||||||
| Springer , 1939 |
The narrow fin Glatthai ( Mustelus norrisi ) is a shark species in the genus Mustelus within the family of Glatt sharks . It lives in the western Atlantic and is very similar to the dark smooth shark . According to the IUCN , it is unclear whether Mustelus norrisi is really a separate species.
features
Mustelus norrisi is a rather slender shark with quite large oval eyes, a pointed snout and a short head. It also has small pectoral fins and an asymmetrical caudal fin. The first dorsal fin starts far back and the second dorsal fin is much larger than the anal fin. They are sickle-shaped and have rear edges covered with skin teeth. The tapering lobe at the front end of the pectoral fin is striking. This is directed backwards. The shark is gray on the back and fades to a dirty white on the belly. It reaches a maximum length of approx. 1.1 meters and weighs a maximum of 13.8 kilograms. On average, male sharks are around 75 centimeters long and females around 90 centimeters long. The narrow-finned smooth shark reaches sexual maturity with a length of approx. 58 centimeters in males and approx. 65 centimeters in females. It has numerous blunt and small teeth that are comparable to molars. They have blunt humps and are arranged asymmetrically.
The snout
The jaw
The upper rows of teeth
The lower rows of teeth
Occurrence
The fine-fin shark is native to the western Atlantic , along the US east coast from Alabama, Florida, Georgia, South Carolina, Texas to the Gulf of Mexico and Venezuela. Originally it was assumed that this species is only native to this area, but new discoveries show that this species can also be found in southern Brazil. Most often it is found on the west coast of Florida.
behavior
The narrow-fin smooth shark is found close to the ground on the continental shelf over sandy or muddy ground, mostly from the beach to waters of about 80 meters deep. In winter it migrates closer to the coast and can be found in waters from a depth of about 50 meters. It mainly eats crustaceans, shrimp and small fish. The narrow-finned smooth shark is hunted by larger sharks such as the black shark , the small blacktip shark or the great hammerhead shark .
It is a viviparous species with a yolk sac placenta , usually between 7 and 14 young are born. These are approximately 30 centimeters long and are born between late winter and spring.
Danger
Little is known about the populations of this species, and the shark is likely to be found frequently in its patchy range. Since it is often close to the coast, it is likely to be often bycatch with fishermen in trawls. If one uses the population of the very similar dark shark for comparison, one sees that the stock was abundantly fished at the beginning of the recordings, but then it was declining and it is almost absent nowadays. One suspects a similar process in the narrow-finned smooth shark.
The Brazilian population is poisoned by mercury.
There are currently no measures to protect this species, but the IUCN urges that further research be done urgently on safe taxonomic status, catch quotas and population quotas.
Since there is insufficient data , it is not possible to make an adequate assessment of the risk of extinction. However, all assumptions indicate that the species is threatened by exploitation.
supporting documents
- ↑ a b Smooth Shark on Fishbase.org (English)
- ↑ a b c d Mustelus norrisi in the Red List of Threatened Species of the IUCN 2017-1. Posted by: Jones, LM, Kyne, PM & Carlisle, AB, 2008-12-01.
- ↑ a b c d e f Taylor Chapple: Narrowfin Smooth-hound. Florida Museum of Natural History, accessed August 2, 2017 .
- ^ A b Leonard JV Compagno : FAO SPECIES CATALOG. Vol.4. Sharks of the world. Part 2. Carcharhiniformes, 1984, ISBN 92-5-101383-7 , pp. 421-422 ( PDF; 27 MB ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. ).
Web links
- Engnasen-Glatthai on Fishbase.org (English)
- Mustelus norrisi inthe IUCN 2017-1 Red List of Threatened Species . Posted by: Jones, LM, Kyne, PM & Carlisle, AB, 2008-12-01.