Galeorhinus galeus

Galeorhinus galeus

The school shark or tope, tope shark, snapper shark, soupfin shark (Galeorhinus galeus Linnaeus, 1758) is a shark belonging to the Triakidae family.

Systematic –
From a systematic point of view it belongs to:
Eukaryota domain,
Kingdom Animalia,
Phylum Chordata,
Class Chondrichthyes,
Subclass Elasmobranchii,
Order Carcharhiniformes,
Triakidae family,
Genus Galeorhinus,
Species G. galeus.
The term is basionym:
– Squalus galeus Linnaeus, 1758.
The terms are synonymous:
– Carcharhinus cyrano Whitley, 1930;
– Eugaleus galeus (Linnaeus, 1758);
– Galeorhinus australis (Macleay, 1881);
– Galeorhinus chilensis (Pérez Canto, 1886);
– Galeorhinus cyrano Whitley, 1930;
– Galeorhinus galeo (Linnaeus, 1758);
– Galeorhinus vitaminicus de Buen, 1950;
– Galeorhinus zyopterus Jordan & Gilbert, 1883;
– Galeus australis Macleay, 1881;
– Galeus canis Bonaparte, 1834;
– Galeus chilensis Pérez Canto, 1886;
– Galeus communis Owen, 1853;
– Galeus linnei Malm, 1877;
– Galeus molinae Philippi, 1887;
– Galeus nilssoni Bonaparte, 1846;
– Galeus vulgaris Fleming, 1828;
– Galeus zyopterus (Jordan & Gilbert, 1883);
– Notogaleus australis (Macleay, 1881);
– Notogaleus rhinophanes (Péron, 1807);
– Squalus rhinophanes Péron, 1807.

Geographic Distribution and Habitat –
The Galeorhinus galeus is a shark with a widespread distribution and present in the north-eastern Atlantic and the Mediterranean Sea, where it is rare, and in the south-west Atlantic, where it is found between Patagonia and southern Brazil. It is also found along the coast of Namibia and South Africa. It is present in the northeast Pacific, between British Columbia and Baja California, and in the southeast Pacific off Chile and Peru. Finally, populations are also found along the southern coasts of Australia, including Tasmania and New Zealand.
Its marine habitat is mainly that of subtropical seas near the seabed around the coasts in temperate waters, up to a depth of about 800 m.

Description –
The Galeorhinus galeus is a small shark that can reach a length of almost 2 m; adult specimens vary from 135 to 175 cm for males and from 150 to 195 cm for females. It is dark bluish gray on the upper (dorsal) surface and white on the belly (ventral surface).
It has an elongated snout with a crescent-shaped bump and teeth of similar size and shape in both jaws. They are triangular in shape, small and flat, arranged at an oblique angle facing backwards, serrated and with a notch.
The spiracles are small.
The first dorsal fin is triangular with a straight leading edge and is located just behind the pectoral fins.
The second dorsal fin is approximately the same size as the anal fin and is positioned immediately above it.
The terminal lobe of the caudal fin has a notch and is as long as the rest of the fin. Juveniles have black markings on their fins.

Biology –
Galeorhinus galeus is an ovoviviparous species; her eggs are fertilized internally and remain in the uterus where the developing fetus feeds on the large yolk sac.
Males become mature when they reach a length of about 135 cm and females about 150 cm.
The gestation period is approximately one year and the number of developing pups varies depending on the size of the mother, with the average being approximately 28 to 38.
Puppies from the same litter can have different fathers, probably because females are able to store sperm for a long time after mating.
Females also have traditional pup areas in sheltered bays and estuaries where the pups are born. Juveniles remain in these growing areas while adults move to deeper water.

Ecological Role –
Galeorhinus galeus is the only member of the Galeorhinus genus and is a migratory species. Animals tagged in the UK have been recovered in the Azores, the Canary Islands and Iceland. Individuals classified in Australia traveled distances of 1,200 km along the coast and others appeared in New Zealand.
This shark feeds mainly on fish. Examination of the stomach contents of fish caught off California showed that they feed by consuming whatever fish were most available. Their diet was predominantly sardines, midshipmen, flatfish, rockfish and squid. Feeding takes place both in open water and near the seabed since sardines and squid are pelagic animals, while the rest are benthic species.
As for its relationship with humans, these fish have been caught and consumed for centuries.
For example, they are a traditional Māori resource in New Zealand, where they are known by the Māori name kapetā. Hapū traveled across Northland to attend special events in Rangaunu Harbour, where kapetā could be fished for two days. The meat could be eaten fresh or preserved, and oil from shark livers was mixed with plant substances and red ocher to create cosmetics.
School shark meat is consumed in Andalusian cuisine, where it is usually known as cazón. Recipes include the traditional cazón en adobo in the mainland and tollos in the Canary Islands. In Mexican cuisine, the term cazón refers to other species and is prepared in a similar way. In the UK, the meat is sometimes used in “fish and chips” as a substitute for the more common cod or haddock. In Greek cuisine, it is known as galéos (γαλέος) and is usually served with skordalia (σκορδαλιά), a sauce made from mashed potatoes or soaked white bread, with mashed garlic and olive oil.
In Venezuela it is used for many dishes, the most typical of which is the preparation of dogfish empanadas and/or arepas. This fish is boiled, then seasoned to taste with onion, paprika, chopped chilli pepper, etc.; A stew is prepared and an infinite number of meals are prepared with it. It is mainly consumed on Margarita Island and throughout the east of the country.
In fact, it is used to prepare a cake called Torta de Cazón in that region, which has slices of fried plantains added. Also very well known is the so-called Margariteño pavilion, in which the minced meat is replaced by the aforementioned stew. In Colombia, on the Pacific coast, they usually call it – Toyo – its preparation is normally a stew – Sudao – with coconut, rice and slices of ripe or green banana.
Before 1937, this shark was caught in California to supply a local market with shark fillets, and the fins were dried and sold in East Asia. Around that date, laboratory tests on his liver showed that it had a higher vitamin A content than any other fish tested. Subsequent to this discovery, it became the subject of a much larger scale fishery which developed due to the high prices obtainable for the fish and its liver. It became the main source of vitamin A supply in the United States during World War II, but was overexploited; thus populations were reduced and the number of fish caught decreased. Its oil was replaced by a similar product made from dogfish (Squalus suckleyi) and later by lower-potency fish oils from Mexico and South America.
This shark is one of the most important species in South Australia’s commercial fisheries. It is fished throughout its range and heavily exploited.
Due to its high exploitation and the reduction of habitats, the IUCN lists G. galeus as in danger of extinction in its Red List of Threatened Species. Although it is widely distributed, it is threatened by overexploitation in many parts of its range, where it is targeted for liver oil, meat and fins. It is mainly caught with gillnets and longlines and, to a lesser extent, by trawling. Hatchlings are sometimes caught along the coast and some breeding areas are subject to siltation and their habitat may degrade. Undersea cables and the magnetic field caused by current flow can disrupt migratory routes.
In 2010, Greenpeace International added school shark to its seafood red list. In June 2018 the New Zealand Department of Conservation classified the school shark as “Not Threatened” with the qualifications “Conservation Dependent” and “Threatened Overseas” under the New Zealand Threat Classification System.

Guido Bissanti

Sources
– Wikipedia, the free encyclopedia.
– GBIF, the Global Information Facility on Biodiversity.
– Gordon Corbet, Denys Ovenden, 2012. Guide to the mammals of Europe. Franco Muzzio Editore.
– John Woodward, Kim Dennis-Bryan, 2018. The great encyclopedia of animals. Gribaudo Publisher.

Photo source:
– https://inaturalist-open-data.s3.amazonaws.com/photos/305115845/original.jpg