Second record of goblin shark Mitsukurina owstoni (Lamniformes: Mitsukurinidae) in Indonesian waters

Four specimens goblin sharks Mitsukurina owstoni Jordan, 1898 with range between c. 150-200 cm of total length were landed and documented on 4 April 2019 at Rigaih fish market, Lhok Timon village, Setia Bakti subdistrict, Aceh Jaya district, Aceh province, Indonesia. This finding is constitute a second record of M. owstoni in Indonesian waters, after a previous record on 20 March 2009 in Pelabuhan Ratu, West Java.


Introduction
Goblin shark or Family Mitsukurinidae is small family containing only single species (Mitsukurina owstoni Jordan, 1898) that patchily distributed in Atlantic, Western Indian ocean and Pacific (Compagno 2001;Ebert et al. 2013). The goblin shark M. owstoni is a large mysterious shark with a bizzare head, very elongated snout forming a flat, blade-like rostrum, small eyes, an elongate, asymmetrical caudal fin without a ventral lobe, partly exposed gill filaments, short rounded fins (except caudal fin), and highly prostrusile jaws with long, slender, awl-like teeth (Last & Stevens 1994;Yano et al. 2007). Although M. owstoni is considered rare in most places when they have been reported, because they are only a very occasional bycatch of deepwater fisheries, they seem likely to be widely distributed and there is nothing to infer any population decline (Ebert et al. 2013;Finucci & Duffy 2018).
The M. owstoni is one of rare and poorly known species because of the difficulty in accessing its deep water habitat and the resulting infrequency of encounters with humans (Compagno 2001;Nakaya et al. 2016). Due to this reason, it is clear why M. owstoni usually overlooked along its potential distribution range. A recent incidental caught of M. owstoni has been recognized from Aceh Province, northern Sumatra. This record is constitute second record of M. owstoni in Indonesia after first record from Pelabuhan Ratu, West Java (Fahmi 2007). This species has not been recorded in Southeast Asian waters of the neighboring countries of Indonesia (Arunrugstichai et al. 2018

Materials and Methods
Four specimens of M. owstoni (c. 150-200 cm of total length) were caught and landed on 4 April 2019, at Rigaih fish market, Lhok Timon village, Setia Bakti subdistrict, Aceh Jaya district, Aceh province, Indonesia (04°41'15''N, 95°31'50''E) (Fig. 1). Not long after landed in fish market, all of these sharks are bought by local people, so all specimens are unable to preserved for scientific purpose. Information of meristic and morphometrics were undocumented, but specific characters of the sharks are seen clearly from photos taken. Two of them are male, based on the appeared claspers on ventral side. Identification of these sharks are therefore from characters available in photographs. Estimated proportional morphometric features of M. owstoni presented as percentage of total lenght based on seen characters in the photographs shown in Table  1. The occurence of M. owstoni from Aceh province was reported by some medias (Booth & Ichsan 2019;Fajar 2019). This information has also been posted in inaturalist.nz, but with an uncorrect location in the map (stated in Banda Aceh, capital city of Aceh province, not Aceh Jaya district) (https://inaturalist.nz/observations?place_id=31686&taxon_id=105913).

Results and Discussions
The sharks caught on 4 April 2020 from Aceh province had distinct characters of unmistakable flat elongated snout, prostrusable jaws, long-cusped slender teeth, short rounded fins except long tail fin (Figs. 2 and 3). These characters are specific characters of M. owstoni compare to other shark guides (Last & Stevens 1994;Compagno 2001, Compagno et al. 2005Ebert et al. 2013). The unique characters of M. owstoni and supported with its diet suggest that this shark is a sluggish mesopelagic species (Duffy 1997).   Table 1. Estimated proportional morphometric features of M. owstoni presented as percentage of total lenght based on seen characters in the photographs. G1 = Goblin shark specimens from Aceh, G2 = Goblin shark specimen Pelabuhan Ratu, West Java (Fahmi 2017).

Characters G1 G2
Snout to mouth (protruded) 5 5.5 Snout to mouth (to upper lip) 10 10.1 Snout to eye 12 13 Snout to pectoral-fin origin 29 26.4 Snout to first dorsal-fin origin 35 33.2 Pectoral fin base 4 4 First dorsal-fin base 6 6.1 Second dorsal-fin base 5 5 Pelvic-fin length 10 9.8 Anal-fin length 10 9.9 The M. owstoni is wide ranging species of sharks but rarely caught because they inhabit deepwater sea habitat, mainly reported from 270-960 m, to at least 1.300 m, and very rarely at the surface or 95-137 m (Shimada & Seigel 2005;Ebert et al. 2013). Although the range of M. owstoni has been known but regional localities not been fully mapped (eg. Parsons et al. 2002;Prokofiev & Kukuev 2009;Rincon et al. 2014).
The presence of M. owstoni in Aceh province is a second record of this deepwater shark in Indonesia. Previously known species from Indonesia reported from a specimen collected on 20 March 2009 in Pelabuhan Ratu, West Java (Fahmi 2017). Mitsukurina owstoni in Pelabuhan Ratu was caught in deepwater fish longline targetting squaloid sharks southwest off Java at about 200 m depth. The lacking of M. owstoni records in Indonesian waters could be combination of rarely caught from deepwater and limited local ichthyologists to determine a good documentation. New additional distribution records of sharks and elasmobranchs have been reported recently from Indonesian waters (Iqbal & Yustian 2016;Iqbal et al. 2019a, b, c;Windusari et al. 2019). More data is needed to learn better understanding of distributional localities of M. owstoni in Indonesian waters, and to determine probably some threats of its populations in the future. Northwest Sumatra and southwest off Java waters, two locations known of M. owstoni in Indonesian waters are part of Sunda Trench where depth variation is about 200-600 m (Raghuram et al. 2018). This deepwater seas is an ideal and potential habitat of M. owstoni.