Galapagos shark

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Galapagos shark
Temporal range: Pliocene–Recent[1]

Least Concern  (IUCN 3.1)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Subdivision: Selachimorpha
Order: Carcharhiniformes
Family: Carcharhinidae
Genus: Carcharhinus
Species:
C. galapagensis
Binomial name
Carcharhinus galapagensis
(Snodgrass & Heller, 1905)
Range of the Galapagos shark
Synonyms

Carcharias galapagensis Snodgrass & Heller, 1905

The Galapagos shark (Carcharhinus galapagensis) is a

pectoral fins
.

The Galapagos shark is an active predator often encountered in large groups. It feeds mainly on bottom-dwelling

least concern
, but it has a slow reproductive rate and there is heavy fishing pressure across its range.

Taxonomy and phylogeny

The Galapagos shark was originally described as Carcharias galapagensis by

Galapagos Islands, hence the specific epithet galapagensis.[3][4]

Garrick (1982) placed the Galapagos shark and the dusky shark at the center of the "obscurus group", one of two major groupings within Carcharhinus. The group consisted of the

allozyme data, naylor (1992) reaffirmed the integrity of this group, with the additions of the silky shark (C. falciformis) and the blue shark (Prionace glauca). The closest relatives of the Galapagos shark were found to be the dusky, oceanic whitetip, and blue sharks.[6]

Distribution and habitat

Galapagos sharks are common around oceanic island reefs.

The Galapagos shark is found mainly off tropical oceanic islands. In the

Galapagos Islands, Cocos Island, the Revillagigedo Islands, Clippperton Island, and Malpelo. There are a few reports of this species in continental waters off the Iberian Peninsula, Baja California, Guatemala, Colombia, and eastern Australia.[7]

The Galapagos shark is generally found over continental and insular shelves near the coast, preferring rugged

open ocean between islands and has been reported at least 50 km (31 mi) from land. Juveniles seldom venture deeper than 25 m (82 ft), while adults have been reported to a depth of 180 m (590 ft).[7]

Description

The Galapagos shark can be difficult to distinguish from other large requiem sharks

One of the largest species in its genus, the Galapagos shark commonly reaches 3.0 m (9.8 ft) long. The maximum length has been variously recorded as 3.3 m (11 ft) to 3.7 m (12 ft).[8] The maximum recorded weight is 195 kg (430 lb) for a 3.0 m (9.8 ft) long female (longer specimens having apparently been unweighed).[9] This species has a slender, streamlined body typical of the requiem sharks. The snout is wide and rounded, with indistinct anterior nasal flaps. The eyes are round and of medium size. The mouth usually contains 14 tooth rows (range 13–15) on either side of both jaws, plus one tooth at the symphysis (where the jaw halves meet). The upper teeth are stout and triangular in shape, while the lower teeth are narrower; both upper and lower teeth have serrated edges.[7]

The first

anal fin. The pectoral fins are large with pointed tips. The coloration is brownish gray above and white below, with a faint white stripe on the sides. The edges of the fins are darker but not prominently marked.[7] The Galapagos shark can be distinguished from the dusky shark in having taller first and second dorsal fins and larger teeth, and it can be distinguished from the grey reef shark in having a less robust body and less pointed first dorsal fin tip. However, these characters can be difficult to discern in the field. These similar species also have different numbers of precaudal (before the tail) vertebrae: 58 in the Galapagos shark, 86–97 in the dusky shark, 110–119 in the grey reef shark.[4][7]

Biology and ecology

A Galapagos shark off Kure Atoll in the Hawaiian Islands.

The Galapagos shark is often the most abundant shark in shallow island waters.

Saint Peter and Paul Rocks along the Mid-Atlantic Ridge, the resident Galapagos sharks have been described as "one of the densest shark populations of the Atlantic Ocean".[10] At some locations they form large aggregations, though these are not true schools.[7]

During group interactions, Galapagos sharks are dominant to

parasite of the Galapagos shark is the flatworm Dermophthirius carcharhini, which attaches to the shark's skin.[12] In one account, a bluefin trevally (Caranax melampygus) was seen rubbing against the rough skin of a Galapagos shark to rid itself of parasites.[13]

Feeding

The Galapagos shark usually hunts near the sea bottom.

The primary food of Galapagos sharks are

Galapagos fur seals (Arctophoca galapagoensis) and sea lions (Zalophus wollebaeki), and marine iguanas (Amblyrhynchus cristatus).[4] While collecting fishes at Clipperton Island, Limbaugh (1963) noted that juvenile Galapagos sharks surrounded the boat, with multiple individuals rushing at virtually anything trailing in the water and striking the boat bottom, oars, and marker buoys. The sharks were not slowed by rotenone (a fish toxin) or shark repellent, and some followed the boat into water so shallow that their backs were exposed.[15]

Life history

Like other requiem sharks, the Galapagos shark exhibits a

mature at 2.1–2.5 m (6.9–8.2 ft) long and 6–8 years old, while females mature at 2.2–2.5 m (7.2–8.2 ft) long and 7–9 years old. Neither sex is thought to reproduce until 10 years of age.[14] The lifespan of this species is at least 24 years.[4]

Human interactions

Galapagos shark hooked on a longline off Hawaii
Galapagos shark being tagged by researchers in the Papahānaumokuākea Marine National Monument

Inquisitive and persistent, the Galapagos shark is regarded as potentially dangerous to humans. However, several live-aboard boats take divers to Wolf and Darwin, the northernmost Galapagos islands, every week specifically to dive in open water with these sharks where they and the scalloped hammerheads accumulate in numbers, and only a few incidents have been reported. They are known to approach close to swimmers, showing interest in

St. Paul's Rocks that "as soon as a fish was caught, a rush of voracious sharks was made at him, notwithstanding blows of oars and boat hooks, the ravenous monsters could not be deterred from seizing and taking away more than half the fish that were hooked".[10] Limbaugh (1963) reported that at Clipperton Island "at first, the small sharks circled at a distance, but gradually they approached and became more aggressive ... various popular methods for repelling sharks proved unsuccessful". The situation eventually escalated to the point at which the divers had to retreat from the water.[15] Excited Galapagos sharks are not easily deterred; driving one away physically only results in the shark circling back while inciting others to follow, whereas using weapons against them could trigger a feeding frenzy.[7]

As of 2008, the Galapagos shark has been confirmed to have attacked three people: one fatal attack in the Virgin Islands;[16] a second fatal attack in the Virgin Islands, at Magens Bay on the north shore of St. Thomas;[17] and a third non-fatal, attack off Bermuda.[7][16] February 2018 saw a non-fatal shark attack in the Galapagos islands that shark photographer Jeremy Stafford-Deitsch suggested may have been carried out by a Galapagos shark, but the species remains unconfirmed.[18]

The

least concern, but its low reproductive rate limits its capacity to withstand population depletion. There is no specific utilization data available, though this species is certainly caught by commercial fisheries operating across many parts of its range.[2] The meat is said to be of excellent quality.[4] While still common at areas such as Hawaii, the Galapagos shark may have been extirpated from sites around Central America and its fragmented distribution means other regional populations may also be at risk. The populations at the Kermadec and Galapagos Islands are protected within marine reserves.[2]

Conservation status

The New Zealand Department of Conservation has classified the Galapagos shark as "Not Threatened" under the New Zealand Threat Classification System with the qualifiers "Conservation Dependent" and "Secure Overseas".[19]

References

  1. ^ Bourdon, Jim. "The Life and Times of Long Dead Sharks". www.elasmo.com. Retrieved 2023-10-03.
  2. ^
    doi:10.2305/IUCN.UK.2019-3.RLTS.T41736A2954286.en
    . Retrieved 19 November 2021.
  3. ^ a b Snodgrass, R.E.; Heller, E. (January 31, 1905). "Papers from the Hopkins-Stanford Galapagos Expedition, 1898–1899. XVII. Shore fishes of the Revillagigedo, Clipperton, Cocos and Galapagos Islands". Proceedings of the Washington Academy is of Science. 6: 333–427.
  4. ^ a b c d e f g Bester, C. Biological Profiles: Galapagos Shark Archived 2010-04-30 at the Wayback Machine. Florida Museum of Natural History Ichthyology Department. Retrieved on April 26, 2009.
  5. ^ Garrick, J.A.F. (1982). "Sharks of the genus Carcharhinus". NOAA Technical Report, NMFS CIRC-445.
  6. S2CID 39697113
    .
  7. ^
    ISBN 92-5-101384-5
    .
  8. ^ "Galapagos shark". FishBase.
  9. ISBN 9780195392944
    .
  10. ^
    JSTOR 1444304
    .
  11. doi:10.1080/10236240601154872
    .
  12. JSTOR 3226388
    .
  13. S2CID 45413817
    .
  14. ^
    S2CID 39220492
    .
  15. ^
    ISBN 0-669-24646-8
    .
  16. ^ a b "ISAF Statistics on Attacking Species of Shark". International Shark Attack File. Florida Museum of Natural History, University of Florida. 24 January 2018.
  17. ^ Randall, J.E. (1963). "A fatal attack by the shark Carcharhinus galapagensis at St. Thomas, Virgin Islands". Caribbean Journal of Science. 3 (4).
  18. ^ Daniel O'Mahony (6 February 2018). "London businessman attacked by shark while snorkelling in the Galapagos Islands". Retrieved 11 February 2022.
  19. OCLC 1042901090
    .

External links

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