FIRST REPORT OF FOUR DEEP-SEA CHONDRICHTHYANS ( ELASMOBRANCHII AND HOLOCEPHALI ) FROM ANDAMAN WATERS , INDIA WITH AN UPDATED CHECKLIST FROM THE REGION

This paper confirms the new distributional records of four rare deep-water chondrichthyans viz. sharpnose sevengill shark, Heptranchias perlo (Bonnaterre, 1788); bluntnose sixgill shark, Hexanchus griseus (Bonnaterre, 1788); bramble shark, Echinorhinus brucus (Bonnaterre, 1788); and sicklefin chimaera, Neoharriotta pinnata (Schnakenbeck, 1931) from the Andaman waters in the Indian EEZ. The above-mentioned four fish species have not been reported earlier from this region. More exploratory surveys in the region are essential to understand the diversity and distribution pattern which is essential for critical management actions. An updated checklist of chondrichthyans known from Andaman and Nicobar waters of India is also presented.


INTRODUCTION
Chondrichthyan diversity in the Indian waters has been vaguely studied (Akhilesh et al. 2014).In comparison to oceanic, deep, or coastal waters off mainland India, chondrichthyan diversity in waters around its major island/archipelago systems i.e., Laccadive Islands in the Arabian Sea and the Andaman and Nicobar Islands in the Bay of Bengal are least known.
The Andaman and Nicobar Islands of India, just fall outside the well-known diversity hotspot, referred to as the Coral Triangle region (Randall 1998, Hoeksema 2007, Kimura et al. 2009), also supports a rich fish diversity.Though there were only few major studies in the region in the end of the19th century (Alcock 1889), the Andaman and Nicobar Islands of India and their surrounding waters, constituting extremely diverse and rich marine habitat, still remain largely unexplored.
Except for checklists and few new reports from waters around the Andaman and Nicobar Islands of India (Soundararajan and Roy 2004, Rajan et al. 2012, 2013, 2016, Devi and Kumaralingam 2014) chondrichthyan diversity of this region is poorly known.However, considering large information gap in the region more concentrated studies are being conducted in the recent past and several ongoing studies are providing better understanding of faunal diversity, fishery trends and improved catch and species composition (Kumar et al. 2015, 2016, Pradeep et al. 2016, 2017,2018, Vinu et al. 2017, Shirke et al. 2017, Tyabji et al. 2018).There is an urgent need to explore this biodiversity hotspot for its better understanding and for conservation actions.Perpetual efforts for documentation of the diversity and updating the checklists with correctly identified species are important for conservation and management of the vulnerable fauna.

MATERIALS AND METHODS
Specimens for the present study were either collected during the deep-sea fishery exploratory survey by FORV Sagar Sampada equipped with HSDT (High Speed Demersal Trawl Net) during 2015-2016 in the Indian EEZ around Andaman waters or from commercial fishing vessels operating in Andaman waters and landed at Junglighat fish landing Centre, Port Blair.Species identification was based on Ebert (2013Ebert ( , 2014) ) and morphometric measurements following Compagno (2001).Collection locations for all materials are presented in Fig. 1.Details of materials examined are provided above description of each species.Collected specimens are deposited in the collection museum of Department of Ocean Studies and Marine Biology, Pondicherry University at Port Blair, India.

RESULTS
Among the fish species surveyed we recorded four that have not been previously reported from the waters of the Andaman and Nicobar Islands.These were the sharpnose sevengill shark, Heptranchias perlo (Bonnaterre, 1788); the bluntnose sixgill shark, Hexanchus griseus (Bonnaterre, 1788); the bramble shark, Echinorhinus brucus (Bonnaterre, 1788); and the sicklefin chimaera, Neoharriotta pinnata (Schnakenbeck, 1931 Diagnosis.Very distinct, medium sized deep-water shark with slender body and pointed snout.Head narrow with seven pairs of lateral gill slits.Single small, narrow, spineless dorsal fin separated from upper caudal origin by space much greater than its base length.Teeth wide and lower teeth comb shaped.Very large eyes, pelvic and anal fin small.Long dorsal lobe of caudal fin, ventral lobe with strong subterminal notch (Ebert 2013).Description.Very distinctive and deep-water shark species with single dorsal fin, body slender, streamlined, sharp pointed conical snout and seven pairs of large gill slits representing unique characteristic.Head length 22.10%-22.76%TL.Single small dorsal fin with origin over inner margin of pelvic fins, dorsal total length 6.59%-8.88%TL, dorsal anterior margin length 6.16%-8.54%TL, dorsal base length 4.94%-6.50%TL, dorsal vertical height 3.99%-4.71%TL.Slightly curved small pectoral fins.Pectoral fin length 9.69%-11.10%TL.Pelvic and anal fin comparatively small.Pelvic height 2.54%-3.33%TL, anal fin vertical height 1.91%-2.54%TL.Prenarial length 2.71%-3.89%TL, eye very large, eye height 1.79%-2.69%TL, eye spiracle space 4.57%-5.25%TL.Gills broadly separated, inter gill length 5.52%-6.70%TL, first gill slit height 6.64%-8.23%TL.Abdomen long, pectoral pelvic space 14.23%-16.01%TL, pelvic anal space 5.65%-6.91%TL, anal caudal space 6.41%-9.32%TL.Dorsal lobe of caudal fin long, upper post ventral caudal margin length 18.08%-20.11%TL, dorsal caudal space 10.17%-12.68%TL.Teeth narrow with hook like cusp and small lateral cusp in upper jaw, teeth in lower jaw large comblike, with large anterior cusp followed by few smaller (Fig. 4).Coloration.Dorsal side of body varying from grey to brown; ventral side of body pale to white; black spot on dorsal fin and upper caudal lobe (prominent in young ones).Remarks.Heptranchias perlo was previously reported from Kollam coast of Arabian Sea, India for the first time by Compagno and Talwar (1985).Since then it has been recorded in commercial fishery mostly in southern coasts of India (off Cochin, Kollam, Tuticorin), where deep-sea fishing operation were conducted and landed mostly as bycatch in deep-sea shrimp bottom trawlers or in longline fishery (AKV personal observation).Heptranchias perlo was reported from the depths of 27-720 m (Compagno 1984) and the presently reported collection depths of 300-535 m are consistent with the earlier reported depth range.This species is not commercially important in Indian fishery, and therefore, in most cases, it is discarded or used for fishmeal preparation.Heptranchias perlo is considered a rare species and it is considered Near Threatened by the IUCN red list of threatened species (Paul and Fowler 2003).Distribution.Widely distributed in tropical and temperate oceans.Diagnosis.Heavily bodied shark with broad head with six pairs of long gill slits and mouth placed ventrally having 6 rows of lower bladelike comb-shaped teeth on each side (Fig. 5).Short and blunt snout.Single dorsal fin placed posterior of body separated from upper caudal fin origin by distance equal or slightly greater than its length (Ebert 2013).
Remarks.Hexanchus griseus has circumglobal distribution in marine tropical and temperate waters as well as continental and insular shelves and slopes of the Atlantic, Indian and Pacific oceans (Nelson 2006).The size at birth of this species is 650-740 mm TL and the maximum reported size is at least 482 cm TL (Compagno et al. 2005).The present specimen (770 mm TL) can be considered a neonatal.Its IUCN Red List status is Near Threatened (Cook and Compagno 2009).Records of H. griseus and its reproductive observations were reported from the Mediterranean Sea (Hemida and Capapé 2002, Capapé et al. 2003, 2004).In India H. griseus has been reported for the first time from Kerala coast (Akhilesh et al. 2010) and since then it has been recorded off southern Indian coasts occasionally as bycatch in trawl or longline fishery (AKV personal observation).

DISCUSSION
The presently reported investigation disclosed new distributional records of sharks Heptranchias perlo, Hexanchus griseus and Echinorhinus brucus from the region and confirmed the occurrence of Neoharriotta pinnata from Andaman waters.Rajan et al. (2012) has enlisted 64 species of chondrichthyans, subsequently several new sharks and batoids were recorded from exploratory surveys and monitoring catch landing of commercial fishing vessesls operated in the region and landed in A&N, Islands, India (Rajan et al. 2013, 2016, Devi and Kumaralingam 2014;Kumar et al. 2015, 2016, Pradeep et al. 2016, 2017, 2018, Vinu et al. 2017, Shirke et al. 2017) and one recent noteworthy study from the region added 12 sharks to Andaman fauna and added 2 sharks to Indian elasmobranch fauna (Tyabji et al. 2018).However, these studies does not include currently reported species.The present study increases the chondrichthyans faunal diversity of Andaman waters of Indian EEZ and provides an updated checklist for the region (Table 1) which also includes, recently collected/observed/photographed several species new to the archipelago during the commercial fishery landing surveys for preparing an updated checklist from region (These records will be published elsewhere).In preparation of this checklist, order of classification arrangement and revised family, genus and species name for some of the sharks, batoids and chimaeras followed Compagno et al. (2005), Ebert (2013Ebert ( , 2014)), Last et al. (2016), Weigmann (2016), and the Catalog of fishes (Eschmeyer et al 2018).The checklist consists of a total 117 chondrichthyan species covering 10 orders and 36 families from Andaman and Nicobar waters with 3 chimaeras, 68 sharks, 3 skates, 34 rays, 3 sawfishes, and 6 guitar fishes.The checklist provided in this paper (Fig. 8) contains also the conservation status of the recorded species of which 10% are listed as Least Concern (9%), Data Deficient (19%), Critically Endangered (4%), Endangered (8%), Vulnerable (33%), Near Threatened (26%).. Specimens representing the majority of the earlier recorded species from the region have not been deposited in national collection, which makes difficult a proper identification of newly recorded species.Because of the lack of the reference specimens, identification is performed in many cases based on the photographic reports and reports of other authors which also have doubtfulness of correct identification (Rajan et al. 2012(Rajan et al. , 2016) ) Due to taxonomic ambiguities, the validity of some fish records needs confirmation and requires further taxonomic studies.Herewith, we would like to emphasize an urgent need for detailed taxonomic studies of chondrichthyans fauna from deep waters of the Andaman Islands of India.More extensive taxonomic studies are needed for better management, planning, and understanding this diverse ecosystem.

Data Deficient (DD) 19%
Fig. 8. Conservation status of chondrichthyans from waters around the Andaman and Nicobar Islands, India

Table 1
Updated checklist of chondrichthyans caught around the Andaman and Nicobar IslandsTable continues on next page.= IUCN global conservation status, N/C = needs confirmation, Q = questionable; LC = least concern, DD = data deficient, CR = critically endangered, EN = endangered, VU = vulnerable, NT = near threatened, NE = not evaluated.