Tope shark (Galeorhinus galeus)

Also known as: liver-oil shark, Miller’s dog, oil shark, penny dog, rig, school shark, snapper shark, soupfin, soupie, southern tope, sweet William, Tiburon, tope, toper, vitamin shark, whithound
  
French: Cagnot, Canicule, Chien De Mer, Haut, Milandré, Palloun, Requin-hâ, Tchi, Touille
Spanish: Bosti, Bostrich, Ca Marí, Cacao, Cassó, Gat, Musola Carallo, Pez Calzón, Pez Peine, Tiburón Trompa De Cristal, Tiburón Vitamínico
KingdomAnimalia
PhylumChordata
ClassChondrichthyes
OrderCarcharhiniformes
FamilyTriakidae
GenusGaleorhinus (1)
SizeMaximum known male length: 193 cm (2)
Maximum known female length: 195 cm (2)

Classified as Vulnerable (VU) on the IUCN Red List (1).

The tope shark, the only member of the genus Galeorhinus, is a large, slender shark with a long snout. Its large mouth contains sharp, triangular teeth, typical of predatory sharks (3). The large almond-shaped eyes are located in front of pronounced spiracles: openings which enable water to be pumped through the gills whilst the shark is resting. The colour of the tope shark varies between bluish and dusky grey on top, and blends to white underneath. The tope shark possesses two dorsal fins; the second, situated over the anal fin, is much smaller than the first. Juveniles less than 61 centimetres in length have black tips on their dorsal and caudal fins and a white edge on the pectoral fins (2) (4).

The tope shark is widespread in temperate waters, except for the northwest Pacific and northwest Atlantic (1) (5).

The tope shark inhabits cold to warm temperate waters. It can be found well offshore, in shallow bays, or at the surf zone, at depths of 2 to 471 metres (4). It often occurs near the bottom, preferring substrates of sand or gravel, but can be found in mid-water or near the surface when feeding (3).

This strong swimmer is an opportunistic predator that attacks schools of fish such as cod, herring, sardines and whiting (3) (4). Although it feeds primarily on bony fish, it also consumes bottom-dwelling animals such as crustaceans and molluscs (3). Tope themselves are prey for larger sharks such as the great white shark (Carcharodon carcharias) (4). Tope sharks occur in small schools that migrate long distances in the higher latitudes of their range where they move towards the equator in winter, and poleward in the summer (4). The schools are known to segregate by sex and age (4), making them especially vulnerable to the effects of fishing (6).

Tope are ovoviviparous (4), a method of reproduction in which embryos develop within eggs that remain inside the mother’s body until they hatch. No placenta is formed, and instead the embryo depends on its own egg yolk for nourishment (3). Gestation is thought to last for about 12 months, and females move inshore to coastal nursery areas in the late summer to give birth (3) (7). Between 6 and 52 pups are born in a litter (4), each measuring about 40 centimetres in length (3). Tope are believed to have a life expectancy of up to 55 years (8).

Tope sharks have been exploited for many years in most parts of its range where its flesh is consumed by humans, its fins are used in shark fin soup, large quantities of vitamin A can be extracted from the oil in the liver, and the skin is made into leather products (1) (4). Large scale commercial fisheries targeting tope continue in many regions, including Uruguay, Argentina, California, southern Australia, and South Africa. Its life-history and biology make this species particularly vulnerable to overexploitation and fisheries for Tope in both California and Australia have collapsed. Currently, the Australian population has recovered and the fishery remains well-managed (9). Tope is also a common and popular catch of sports anglers (4).

Tope sharks may also be threatened by the degradation of inshore nursery areas, as these habitats are particularly vulnerable to human activities (1). The installation of high-voltage cables under the sea bed can induce magnetic and electrical fields across their migration lanes (1), potentially disrupting their migration, and feeding and reproductive biology (6).

There are several measures in place in Australia and New Zealand to regulate tope fisheries, such as limits on the fishing gear used, closed seasons for nursery areas, and limits on the number that recreational fishermen can catch (1) (5). South Africa also has a limit on recreational catches (5), but otherwise, there are few regulations to protect this vulnerable species (1).

For further information on sharks and their conservation see:

Authenticated (09/04/08) by Meaghen McCord, South African Shark Conservancy (SASC).
http://www.sharkconservancy.org

  1. IUCN Red List (March, 2008)
    http://www.iucnredlist.org
  2. Tope Shark Biological Profile, Ichthyology Department, Florida Museum of Natural History (August, 2007)
    http://www.flmnh.ufl.edu/fish/Gallery/Descript/TopeShark/TopeShark.html
  3. Dipper, F. (2001) British Sea Fishes. Underwater World Publications Ltd., Middlesex.
  4. Compagno, L.J.V. (1984) FAO Species Catalogue. Vol 4: Sharks of the World. An annotated and illustrated catalogue of shark species known to date. Part 2. Carcharhiniformes. Food and Agricultural Organization of the United Nations, Rome.
  5. Shark Specialist Group. (2007) Background paper on the conservation status of migratory sharks and possible options for international cooperation under the Convention on Migratory Species. CMS Secretariat, Bonn, Germany. Available at:
    http://www.cms.int/bodies/meetings/regional/sharks/pdf_docs/Doc_04_Background_Paper.pdf
  6. McCord, M. (2008) Pers. comm.
  7. Lucifora, L.O., Menni, R.C. and Escalante, A.H. (2004) Reproductive biology of the school shark, Galeorhinus galeus, off Argentina: support for a single south western Atlantic population with synchronised migratory movements. Environmental Biology of Fishes, 71: 199 - 209.
  8. FishBase (April, 2008)
    http://www.fishbase.org
  9. McCord, M.E. (2005) Aspects of the Ecology and Management of the Soupfin Shark (Galeorhinus galeus). MSc Thesis, Rhodes University, Grahamstown, South Africa.