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Overview

Comprehensive Description

Biology

A rare species found inshore in coastal areas (Ref. 244). Viviparous (Ref. 50449). Specimens range in length from 23.7-61.8 cm TL. Two specimens collected in the 1800s had fresh umbilical scars at 23.7 and 27.4 cm, indicating that the size at birth is close to these sizes; four specimens of 34.1-37.3 cm had well healed, but still obvious umbilical scars. Five males with lengths of 54.8-57.6 cm were found mature (additional material of mature males with lengths of 59.0-62.0 cm and several pregnant females with lengths of 61.0-65.0 cm). Litter size of pregnant females was 6 (Ref. 84280). Undoubtedly taken in local fisheries (Ref. 244).
  • 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. FAO Fish. Synop. 125(4/2):251-655. Rome: FAO. (Ref. 244)
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Distribution

Range Description

The Borneo Shark is an Indo-West Pacific species, recorded from Borneo (Kalimantan, Indonesia and Sarawak, Malaysia) and possibly also China (Chusan Island). Nominal and possible records also exist from Java (Indonesia) and the Philippines but these cannot yet be confirmed (Garrick 1982, Compagno 1984, 1988, in prep. b).
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Indo-West Pacific.
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Western Pacific: Borneo and China. Questionably occurring in Java, Indonesia and the Philippines. Due to its very restricted and very small area of occurrence (Borneo), conservation measures are urgently needed (Ref. 84280).
  • White, W.T., P.R. Last and A.P.K. Lim 2010 Rediscovery of the rare and endangered Borneo Shark Carcharhinus borneensis (Bleeker, 1858) (Carcharhiniformes: Carcharhinidae). pp. 17-28. In P.R. Last, W.T. White and J.J. Pogonoski (eds). Descriptions of new sharks and rays from Borneo. CSIRO Marine and Atmospheric Research Paper no. 32. (Ref. 84280)
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Physical Description

Size

Maximum size: 700 mm TL
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Max. size

70.0 cm TL (male/unsexed; (Ref. 244))
  • 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. FAO Fish. Synop. 125(4/2):251-655. Rome: FAO. (Ref. 244)
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Diagnostic Description

This small species is characterized by the following: snout long and pointed; slender body and tail; alongside each mouth corner is a row of enlarged hyomandibular pores (5-12); upper anterior teeth finely serrated with a single narrow, oblique cusp; distal edge deeply notched and with several cusplets; lower anterior teeth with narrower, similarly oblique cusps; no lateral cusplets; total tooth row counts 23-26/23-25, or 46-50; second dorsal-fin origin well posterior of anal-fin origin, about opposite or just anterior to anal-fin midbase while second dorsal-finorigin to anal-fin origin 2.2-4.1% TL, 0.4-0.9 times second dorsal-fin base; interdorsal space 20.7-22.7% TL; pelvic fins small, anterior margins 4.4-5.8% TL and 35-42% of pectoral anterior margin; first dorsal fin triangular, with nearly straight posterior margin, free rear tip about opposite pelvic-fin origins, length 14.5-17.6% TL, 1.8-2.4 times height, inner margin 1.9-2.8 in base; second dorsal fin much smaller than first and slightly smaller than anal fin, length 7.5-10.2% TL, base 2.0-3.1 times height; height 21-29% of first dorsal fin height; anal fin height 1.1-1.6 times second dorsal height, base 1.1-1.5 times second dorsal-fin base; total vertebral counts 117-121, monospondylous precaudal counts 33-36, diplospondylous precaudal counts 21-26, diplospondylous caudal counts 56-60, precaudal counts 57-63; colour slate-grey dorsally, whitish ventrally with waterline clearly demarcated along head and body, fins no distinct black markings, pectoral fins and lower caudal lobe with whitish margins (Ref. 84280).
  • White, W.T., P.R. Last and A.P.K. Lim 2010 Rediscovery of the rare and endangered Borneo Shark Carcharhinus borneensis (Bleeker, 1858) (Carcharhiniformes: Carcharhinidae). pp. 17-28. In P.R. Last, W.T. White and J.J. Pogonoski (eds). Descriptions of new sharks and rays from Borneo. CSIRO Marine and Atmospheric Research Paper no. 32. (Ref. 84280)
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This is a small, rare inshore coastal shark, known only from five undoubted specimens (four of which were collected from Borneo) and very few valid localities. Virtually all details of its biology and life history parameters are unknown. The maximum size is estimated to be around 70 cm.

Systems
  • Marine
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Environment

demersal; marine
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Life History and Behavior

Life Cycle

Viviparous, placental (Ref. 50449). Distinct pairing with embrace (Ref. 205).
  • Breder, C.M. and D.E. Rosen 1966 Modes of reproduction in fishes. T.F.H. Publications, Neptune City, New Jersey. 941 p. (Ref. 205)
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
C2a(ii)

Version
3.1

Year Assessed
2009

Assessor/s
Compagno, L.J.V.

Reviewer/s
Musick, J.A. & Fowler, S.L. (Shark Red List Authority)

Contributor/s

Justification
This assessment is based on the information published in the 2005 shark status survey (Fowler et al. 2005).

The Borneo Shark (Carcharhinus borneensis) is known from very few records (most from Borneo), none of which are more recent than 1937. It was not recorded in the extensive George Vanderbilt Foundation shark collections in Thailand and Hong Kong (housed at the California Academy of Sciences, San Francisco, USA), the 1996/97 IUCN/SSC Shark Specialist Group and Sabah Fisheries Department survey of marine sharks in markets in Sabah, Borneo (Malaysia), or the 2000/01 WWF shark biodiversity study in the Philippines. Past records of this species are all from areas that have been and are being heavily exploited by artisanal and commercial fisheries and it is likely that these activities have detrimentally affected the Borneo Shark population.

History
  • 2000
    Endangered
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Population

Population
This is a rare shark that has not been recorded since 1937. Only five confirmed specimens are known.

Population Trend
Unknown
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Threats

Major Threats
This rare shark is (or was) found in areas that have been and are being heavily exploited by artisanal and commercial fisheries. These are likely to have detrimentally affected the population of this species, which has not been recorded since 1937.
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Endangered (EN) (C2a(ii))
  • IUCN 2006 2006 IUCN red list of threatened species. www.iucnredlist.org. Downloaded July 2006.
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Management

Conservation Actions

Conservation Actions
No conservation measures are in place for this species.
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: subsistence fisheries
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Wikipedia

Borneo shark

The Borneo shark (Carcharhinus borneensis) is a species of requiem shark, and part of the family Carcharhinidae. Extremely rare, it is known only from inshore waters around Mukah in northwestern Borneo, though it may once have been more widely distributed. A small, gray shark reaching 65 cm (26 in) in length, this species is the only member of its genus with a row of enlarged pores above the corners of its mouth. It has a slender body with a long, pointed snout and a low second dorsal fin placed posterior to the anal fin origin.

Almost nothing is known about the natural history of the Borneo shark. It is viviparous like other requiem sharks; the females bear litters of six pups, which are provisioned through gestation by a placental connection. The International Union for Conservation of Nature last assessed this species as Endangered, at which time it had not been seen since 1937. While an extant population has since been found, the Borneo shark continues to merit conservation concern given its highly limited range within heavily fished waters.

Taxonomy and phylogeny[edit]

Dutch ichthyologist Pieter Bleeker originally described the Borneo shark as Carcharias (Prionodon) borneensis in an 1858 issue of the scientific journal Acta Societatis Regiae Scientiarum Indo-Neêrlandicae. He based his account on a newborn male 24 cm (9.4 in) long, caught off Singkawang in western Kalimantan, Borneo.[3] Later authors have recognized this species as belonging to the genus Carcharhinus.[4] Before 2004, only five specimens of the Borneo shark were known, all of them immature and collected before 1937.[1] In April and May 2004, researchers from Universiti Malaysia Sabah discovered a number of additional specimens while surveying the fishery resources of Sabah and Sarawak.[2]

The evolutionary relationships of the Borneo shark are uncertain. Jack Garrick, in his 1982 morphological study, did not place it close to any other member of the genus.[5] Leonard Compagno in 1988 tentatively grouped it with the smalltail shark (C. porosus), blackspot shark (C. sealei), spottail shark (C. sorrah), creek whaler (C. fitzroyensis), whitecheek shark (C. dussumieri), hardnose shark (C. macloti), and Pondicherry shark (C. hemiodon).[6] The Borneo shark resembles the sharpnose sharks (Rhizoprionodon) in certain traits, for example the enlarged pores by its mouth. Nevertheless, other aspects of its morphology firmly place it within Carcharhinus.[2]

Description[edit]

The Borneo shark is slim-bodied, with a long, pointed snout and oblique, slit-like nostrils preceded by narrow, nipple-shaped flaps of skin. The eyes are rather large and circular, and equipped with nictitating membranes. The corners of the sizable mouth bear short, indistinct furrows, and immediately above are a series of enlarged pores that are unique within the genus. There are 25–26 upper and 23–25 lower tooth rows. The upper teeth have a single, narrow, oblique cusp with strongly serrated edges, and large cusplets on the trailing side. The lower teeth are similar, but tend to be more slender and finely serrated. The five pairs of gill slits are short.[4][2]

The pectoral fins are short, pointed, and falcate (sickle-shaped), while the pelvic fins are small and triangular with a nearly straight trailing margin. The first dorsal fin is fairly large and triangular, with a blunt apex sloping down to a sinuous trailing margin; its origin lies over the free rear tips of the pectoral fins. The second dorsal fin is small and low, and originates over the middle of the anal fin base. There is no ridge between the dorsal fins. The caudal peduncle bears a deep, crescent-shaped pit at the origin of the upper caudal fin lobe. The asymmetrical caudal fin has a well-developed lower lobe and a longer, narrow upper lobe with a strong ventral notch near the tip. The dermal denticles are small and overlapping, each with three horizontal ridges leading to marginal teeth. This species is slate-gray above, darkening towards the tips of the dorsal fins and upper caudal fin lobe; some specimens have irregular rows of small, white blotches, which may be an artifact of handling. The underside is white, which extends onto the flanks as a vague pale band. There are faint, lighter edges on the pectoral, pelvic, and anal fin trailing margins. The largest known specimen measures 65 cm (26 in) long.[4][2]

Distribution and habitat[edit]

The Borneo shark is only known to inhabit the coastal waters of Sarawak.

All recent specimens of the Borneo shark have been collected solely from fishery landing sites at Mukah in Sarawak, despite thorough surveys across the rest of Borneo (including at the locality of the type specimen). Thus, its range may now be restricted to shallow, inshore waters in northwestern Borneo.[2][7] Of the five earlier specimens, four came from Borneo and one from Zhoushan Island in China, hinting at a wider historical distribution. This species was also recorded from Borongan in the Philippines in 1895, and Java in 1933; these records cannot be substantiated and there have been no subsequent sightings from these areas.[2]

Biology and ecology[edit]

Bony fishes are probably the main food of the Borneo shark.[8] It is viviparous like other requiem sharks, with the developing embryos provisioned by the mother through a placental connection formed from the depleted yolk sac. The litter size is six, and the pups are born at close to 24–28 cm (9.4–11.0 in) long. From the available specimens, the length at sexual maturity can be surmised to be under 55–58 cm (22–23 in) in males and under 61–65 cm (24–26 in) in females.[2][8]

Human interactions[edit]

The International Union for Conservation of Nature last assessed the Borneo shark as Endangered, based on 2005 data that do not include the recent specimens from Mukah. Previously, several fishery surveys within its supposed historical range had failed to find it.[1] The Borneo shark's conservation status remains precarious given its very small range in waters subjected to intensive artisanal and commercial fishing.[2] It is caught by line gear and used for meat, though it has minimal commercial significance.[7]

References[edit]

  1. ^ a b c d Compagno, L.J.V. (2005). "Carcharhinus borneensis". IUCN Red List of Threatened Species. Version 2011.2. International Union for Conservation of Nature. 
  2. ^ a b c d e f g h i White, W.T.; Last, P.R.; Lim, A.P.K. (2010). "Rediscovery of the rare and endangered Borneo Shark Carcharhinus borneensis (Bleeker, 1858) (Carcharhiniformes: Carcharhinidae)". In Last, P.R., W.T. White, and J.J. Pogonoski. Descriptions of New Sharks and Rays from Borneo. CSIRO Marine and Atmospheric Research. pp. 17–28. ISBN 978-1-921605-57-4. 
  3. ^ Bleeker, P. (1858). "Twaalfde bijdrage tot de kennis der vischfauna van Borneo. Visschen van Sinkawang". Acta Societatis Regiae Scientiarum Indo-Neêrlandicae 5 (7): 1–10. 
  4. ^ a b c Compagno, L.J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Food and Agricultural Organization. pp. 458–459. ISBN 92-5-101384-5. 
  5. ^ Garrick, J.A.F. (1982). Sharks of the genus Carcharhinus. NOAA Technical Report, NMFS CIRC 445.
  6. ^ Compagno, L.J.V. (1988). Sharks of the Order Carcharhiniformes. Princeton University Press. pp. 319–320. ISBN 0-691-08453-X. 
  7. ^ a b Last, P.R.; White, W.T.; Caire, J.N.; Dharmadi; Fahmi; Jensen, K.; Lim, A.P.K.; Mabel-Matsumoto, B.; Naylor, G.J.P.; Pogonoski, J.J.; Stevens, J.D.; Yearsley, G.K. (2010). Sharks and Rays of Borneo. CSIRO Publishing. pp. 92–93. ISBN 978-1-921605-59-8. 
  8. ^ a b Voigt, M.; Weber, D. (2011). Field Guide for Sharks of the Genus Carcharhinus. Verlag Dr. Friedrich Pfeil. pp. 49–50. ISBN 978-3-89937-132-1. 
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