chapter 8 Diversity and Abundance of Chondrichthian Fishes in Andaman and Nicobar Islands

P.T. Rajan, C.R. Sreeraj, and K. Venkataraman

Abstract Chondrichthian fishes are represented by sharks, rays and skates that form one of the important commercial fish fauna. The coral reef, offshore and mangrove habitats appear to be inhabited by numerous sharks and ray species, with 5% of fish species being recorded from these islands. This chapter presents a total of 65 species under 40 genera, distributed among 21 families in Andaman and Nicobar Islands with the development of shark fishing and providing new baseline data on diversity abundance, fishing effort and shark catches.

eywords Abundance Andaman Chondrichthian fishes Diversity Shark

8.1 Introduction

Andaman and Nicobar islands, situated in the Bay of Bengal between 6°451-130451N and 92°101-940151E, consist of 572 islands coastline of 1,962 km and bring in for India an exclusive economic zone (EEZ) of 600,000 km2. The shelf topography of these islands shows frequent rises supporting coral reefs, which are characterized as fringing reefs on the eastern side and barrier reefs off west coast; the depressions are known as passages and straits. Besides coral reefs, the shore is composed of rocky and sandy areas and vast stretches of mangrove swamps. Due to the varied marine habitats, ichthyofauna of these islands is observed to be one

P.T. Rajan (a) C.R. Sreeraj Zoological Survey of India, Andaman and Nicobar Regional Centre, Port Blair 744 102, Andaman and Nicobar Islands, India c-mail: rajanptandaman@rediffmaii.com; crsreeraj@gmail.com

K. Venkataraman Zoological Survey of India, Prani Vigyan Bhawan, M-Block, New Alipore, Kolkata 700 053, India

. Venkataraman et al. (eds.), Ecology of Faunal Communrties on the Andaman 117 Nicohar Islands, DO1 10.1007/978-3-642-28335-2-8,

Springer-Verlag Berlin Heidelberg 2012

P.T. Rajan et al.

of the most diverse in the world. The fish diversity in these waters also receives special interest in terms of marine zoogeography because of the confluence of Andaman Sea fishes with Western Pacific and the Indian Ocean. However, given the extreme fragility of these ecosystems, the biodiversity is under heavy threat. The diversity, with the developmental pressures faced, may be under declination. Socio-economically, the fishery industries here tend a significant portion. However, among others, sustainable marine fishery is one form of untapped coastal wealth so far in these islands. On these accounts, this chapter brings about the information on diversity and abundance of sharks and rays of Andaman and Nicobar Islands.

There are no studies on elasmobranchs in Andaman and Nicobar, but various researchers reported sharks from Indian waters (Day 1875-78, 1888; Misra 1950; Talwar 1990; Compagno 1984; Sivasubramanium 1992; Hanfee 1996; Raje et al. 2002; Venkataraman et al. 2003). Coral reef, offshore and mangrove habitats appear to be inhabited by numerous sharks and ray species, with 5% of fish species being recorded from these islands. Elasmobranches are represented by sharks, rays and skates that form one of the important commercial fish fauna; the present works report a total of 65 species under 40 genera, distributed among 21 families in these islands.

8.2 Results and Discussion

A total of 1,485 species of fishes under 603 genera belonging to 177 families are represented from these islands, of which 400 species having commercial signifi- cance as food fishes. Among the fishes, 73.38% of species are recorded as coral inhabitants (i.e. 1,089 species). Besides 277 species from mangroves, 152 species from seagrass meadow, 23 species from freshwater streams and 101 species from offshore environment, 158 species were commonly observed as overlap between mangrove, seagrass, coral reefs and offshore ecosystems. The family-wise distribu- tion of sharks, rays and skates in Andaman and Nicobar Islands is presented in Tables 8.1 and 8.2; Figs. 8.1-8.4.

Fisheries that catch elasmobranch species in the Andaman and Nicobar Islands can be divided into three general categories, namely, directed commercial, incidentallby-catch commercial and incidentallby-catch recreational. Directed fisheries are those that target sharks, skates and rays, whereas incidental fisheries catch sharks secondarily while fishing for other species. In virtually every fishery (e.g. gillnet, long line, trawl, purse seine, headgear), there are varying levels of incidental catches and/or by-catch of sharks.

Exploitation of sharks developed rapidly in these islands from 2000, and most of the sharks were targeted by artisanal fisheries, not only for their fins but also for their meat and liver oil. This became the main reason for the exploitation of sharks. There was also an increase in landings made by artisanal fishermen and a rapid and regular increase in the fishing effort with more boats, more efficient fishing

8 Diversity and Abundance of Chondrichthian Fishes

Table 8.1 Family-wise Family Genera Species distribution of sharks, rays and skates in Andaman and Chimaeridae 1 1 Niwbar Islands Rhinochirnaeridae 1 1

Herniscyllidae 1 3 S tegosmatidae Proscylliidae Carcharhinidae Scyliorhinidae Hernigaleidae Sphymidae Lamnidae Alopiidae Squalidae Centrophoridae Pristidae Narcinidae Rhinidae Rhinobatidae Rhynchobatidae Rajidae Dasyatidae Myliobatidae

Total

equipment, the introduction and expansion of new technologies, through the utili- zation of larger fishing canoes (up to 20 m), with more powerful engines (above 30 HP). Today, the increasing market for shark fins is the main driving force behind the increasing pressure to target sharks. Sharks are highly vulnerable to fishing pressure. Therefore, the combined effects of targeted artisanal fishing and signi- ficant incidental by-catch by industrial fisheries could mark the end of the once abundant populations in our region. Cartilaginous fishes are top predators. Except in some rare cases, they have no natural predators, unless they meet a bigger shark. Therefore, they regulate the balance among marine ecosystems. Most species reach sexual maturity after 10 years; their gestation is also very long. Their reproductive cycles are annual or biennial. In addition, their fertility rate is very low, and most species produce not more than eight pups per litter. Only a few species or groups of species have litters with dozens of pups, such as the hammerhead shark Sphyrna spp. and the tiger shark Galeocerdo cuvieri or even several hundred for the whale shark Rhincodon typus. The youngest age groups contribute relatively little to the repro- ductive output, and it is of course the individuals in the oldest age groups that disappear the most quickly from a population when targeted by fishing. In an overfished population in which the large breeding sharks have been removed, the reproductive effort of female adults is lower than in a healthy population. Therefore, continuing to exploit an overfished population further accelerates its collapse.

i'

Andaman and Nicobar khuh ' Sl. no. Orderffarnily s m m C h i m a e ~ y o ~ ~ '1. Chimaaidet(chimaeras) Hydrolugus sp. 2. p - i P = Nedrrrrriosta sp.

chimarras) Orectolobiformes 3. Hemiscyllidae (bsmboo sharks) Chiloscplliwn grisewn (Muller & Henle, 1838) 4. Chiloscylliwn indicwn (Grnelin. 1789) 5. Chiloscylliwn plrncrcmun (Mullex & M e , 1838) 6. Stegostomatidae (zebra sharks) Stegostoma fasciotum (Hermann. 1783) Carchprhinifonns 7. Roscylliidae @mqUids) Erkhnis radclifii (Smith, 1913) 8. Carcharhinidae (requiem Carcharhinus albimargimtus (Ruppell. 1837) 9. w) Carcharhim amblyrhynchos (Bkeker, 1856) 10. Carcharhinus brevipinna (Muller & 11. Carcharhinus dussumieri (Muller & 12. Carcharhinus hem'odon (Valenciennes, 1839)' 13. Carcharhinus limbatus (Muller & Henle, 1839) 14. Carcharhinus longinuurus (Poey, 1816) 15. Carcharhinus macloti (Muller & Henle, 1839) 16. Carcharhinus melatwpterus (Quoy & Gaimard, 1 17. Carcharhinus seolei (Pietschmann, 191 3) 18. Carcharhinus sorrah (Muller & Henle, 1839) 19. Gcrleocerdo cwieri (Pemn & Le Sueur, 1822) 20. Glyphis gangeticus (Muller & Henle. 1839)' 21. Laxodon macrorhim Muller & Henle, 1839 22. Negaprion ocuti&ns (Ruppell, 1837) 23. Prionace glauca (Linnaeus, 1758) 24. Rhizopri&n acutus (RuppeU.1837) 25. Rhizoprionodon oligolinx (Springer. l%4) 26. Scoliodon laticaudur (Muller & Haale.1838) 27. Triaenodon obesus (RuppeI1,1837) 28. Scyliorhinidae (cat sharks) Apristurus investigatoris (Misra, 1962) 29. Holacluru hispidus (Alcock, 1891) 30. Hemigaleidae Chaemgaleus macrostoma (Bleeker. 1852) 31. Sphymidae (hammemead Euspbym blochii (Cuvier, 1816) 32. -1 Sphytm lcwini ( G r i m & Smith. 1834) 33. Sphytm moRMan (RuppeU, 1837) 34. Sphyna ndcs (Valeacirmes, 1822) 35. Sphytm zygaem (Linnaeu~, 1758) ~ f o m s 36. Lamnidae (msckerel sharks) Iswus oxyrinchus ( R d h e ~ q ~ e . 18 10) 37. Alopiidae (thresher sharks) Alopias pehgius (Nakamml935) 38. AIopias s~rci l iosus (Lowe1839) 39. Alopias vulpinus mm, 1788)

8 Diversity and Abundance of Chon 121

Table 8.2 (continued) S1. no. Order/family

Squaliformes 40. Squalidae (dogfishes) &wlur megalops (Mac Leay, 188 1) 4 1. Centrophoridae Centropborus acus (Garman, 1906) Pristifonnes 42. F'ristidae (saw fishes) Anoxypristis cuspidata (Latham, 1794)= 43. Pristis microdon (Latham, 1794)' 44. Pristis zijsron (Bleeker, 185 1)' Torpediniformes 45. Narcinidae Narke sp. Rajiformes 46. Rhinidae (guitarfishes) Anoxypristis cuspidata (Bloch & Scheider, 1801) 47. Rhinobatidae (guitarfishes) Rhinobatos granularus (Cuvier, 1829) 48. Rhinobatos thouin (Shaw,1804) 49. Rhynchbatidae Rhynchobatus djiddensis (Forsskal, 1775)a 50. Rajidae (skates) Crurirja andamanica (Lioyd, 1909) 5 1. Dasyatidae (stingrays) Dasyatis kuhlii (Muller & 52. Dasyatis thetidis (Ogilby, 18 53. Dasyatis zugei (Muller & Hen 54. Gymnura poecilura (Shaw, 18 55. Himantura gerrardi (Gray 56. Himantura irnbricata (Bloch 57. Himantura uarnak (ForsskalJ7 58. Pastinachus sephen (Forsskal, 59. Taeniura l p m (Forsskal,l77 60. Taeniura meyeni (Muller & Henle, 1841) Myliobatiformes 61. Myliobatidae (eagle rays and Aetobatus narinari (Euphrasen, 1790) 62. devil rays) Aetomylaeus nichofi (Bloch & Schneider, 1801) 63. Manta birostris (Donndorff, 1792) 64. Mobula diabola (Shaw, 1804) 65. Rhinoptera javanica (Muller & Henle, 1841) aProtected under Wildlife Protection Act (1972)

Other aspects of shark behaviour must be considered, for example, segregation by size and by sex. In some species, schools of sharks are composed of a high-majority (or only) individuals of the same sex and/or in the same age group. Catches of Sphyrna lewini (small hammerhead sharks) usually occur in schools of juvenile sharks, with many individuals of about the same size. These biological characteristics explain the great vulnerability of sharks to exploitation. In addition, fishermen are familiar with their migrations and/or groupings linked to their biological cycles, which results in targeted and intensified fishing practices. For this reason, artisanal fishing can have extremely destructive effects on these populations.

P.T. Rajan et al.

Pastinachus seohen

8.3 Conservation Status of Sharks in Andaman and Nicobar Islands

The exploitation of sharks in commercial fisheries for their fins, meat, liver oil, cartilage and other parts remains largely unregulated in Andaman and Nicobar Islands. Overfishing, excessive by-catch, a lack of scientific data, poor management, shark fining and the lack of political will to adopt best practices have led to declines in populations of many shark species in near future. To reverse these declines, establish shark sanctuaries within their waters, including their full exclu- sive economic zones (EEZ), where sharks are fully protected from exploitation. Devise and implement effective National Plans of Action for sharks. End fishing of sharks that are threatened or near threatened with extinction and sharks that do not have science-based management plans in place. t legislation prohibiting the removal of shark fins at sea. Work to eliminate catch. Enact immediate protections for species listed by as the Convention

8 Diversity and Abundance of Chondrichthian Fishes

. &its that are based on sound science. ~mprove species-specifi-c tt& data collection. Generate high-quality scientific research on

a d nationd, and intanadond 'frade to

nets and thrown back, dead, into the

P.T. Rajan et al.

carcnamfrmssorran tvalencleTrReSl839J Spot-Tail Shark

Fig. 8.3 Sharks fishes of Andaman and Nicobar Islands

coastal species and are therefore directly impacted by coastal fishing activities. Furthermore, by-catch of sharks by deep-sea fisheries has been increasing over the past 10 years. Some species are extinct locally-for example, Pristidae (sawfish), the only remaining population of which is in some of the remote islands, like the great hammerhead shark (Sphyrna mokarran) and the lemon shark (Negaprion acutidens)-and are threatened. Furthermore, the proportion of large breeding groups has decreased in all large shark species. Several species are endangered or even critically endangered; the following species are of particular concern: Anoxypristis cuspidata, Pristis microdon, Pristis zijsron, Rhynchobatus djiddensis, Sphyrna mokarran, Rhinobatos granulatus, Sphyrna lewini, Sphyrna zygaena and Rhincodon typus; pelagic thresher, Alopias pelagicus; bigeye thresher, A. superciliosus; thresher, A. vulpinus; shortfin mako, Isurus oxyrinchacs; and oceanic whitetip, Carcharhinus longimanus. The following specks d elasmobranchs are listed under Wildlife Protection Act (1972), namely, Carcha hemiodon, Glyphis gangeticus, Anoxypristis cuspidata, P & @ . & r h , P F & ~ zijsron and Rhynchobatus djiddensis. In Nicobar Islands

. A,, . i s &.

8 Diversity and Abundance of Chondrichthian Fishes

:: Carcharhinus wheeleri Garrick1 982 Blacktail Reef

Carcharhinus falciformis (Bibron.1839) Silky Shark

Fig. 8.4 Shark fishes of Andaman and Nicobar Islands

been using a traditional participative management approach for years. Shark finning is prohibited by national bans in USA, the European Union, South Africa, Brazil and Costa Rica (Fowler et al. 2005) and regulated through administrative measures in other countries including Ausbalia and Canada.

Acknowledgements The authors wish to thank Ministry of Environment and Forests, New Delhi, and Dr. C. Raghunathan, Officer-In-Charge, Zoological Survey of India, Port Blair, for the support. We also acknowledge Dr. Rema Devi, Joint Director; Dr. Rajkumar Rajan, Scientist, Zoological Survey of India, Chemai and Dr. John E. Randall, Bishop Museum, Honolulu, Hawaii, USA, for their valuable comments and discussions on related topics.

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