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Charles Darwin University A rare contemporary record of the Critically Endangered Ganges shark Glyphis gangeticus Jabado, R. W.; Kyne, P. M.; Nazareth, E.; Sutaria, D. N. Published in: Journal of Fish Biology DOI: 10.1111/jfb.13619 Published: 01/05/2018 Document Version Peer reviewed version Link to publication Citation for published version (APA): Jabado, R. W., Kyne, P. M., Nazareth, E., & Sutaria, D. N. (2018). A rare contemporary record of the Critically Endangered Ganges shark Glyphis gangeticus. Journal of Fish Biology, 92(5), 1663-1669. https://doi.org/10.1111/jfb.13619 General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Download date: 28. Sep. 2021 This is the peer reviewed version of the following article: Jabado, R. W., Kyne, P. M., Nazareth, E. and Sutaria, D. N. (2018), A rare contemporary record of the Critically Endangered Ganges shark Glyphis gangeticus. J Fish Biol, 92: 1663-1669. doi:10.1111/ jfb.13619 , which has been published in final form at https://doi.org/10.1111/jfb.13619. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. 1 Running headline: Critically Endangered Ganges Shark Record 2 3 A rare contemporary record of the critically endangered Ganges shark Glyphis 4 gangeticus 5 6 * † ‡ § 7 R. W. JABADO , P. M. KYNE , E. NAZARETH , D. N. SUTARIA 8 9 * Gulf Elasmo Project, P.O. Box 29588, Dubai, United Arab Emirates, † Research Institute 10 for the Environment and Livelihoods, Charles Darwin University, Darwin, NT 0909, 11 Australia, ‡ Saint Xavier College, Mumbai, P.O. Box 400001, India, § College of Marine and 12 Environmental Sciences, James Cook University, Townsville, QLD 4811, Australia 13 14 15 16 17 18 19 20 21 22 23 24 * Author to whom correspondence should be addressed. Tel.: +971 50 8885687; email: [email protected] 25 26 The first record of the Ganges shark Glyphis gangeticus from anywhere in its range in over a 27 decade is reported from the Arabian Sea. One female specimen was recorded at Sassoon 28 Docks in Mumbai, India in February 2016, measuring 266 cm total length. In light of the 29 critically endangered status of this species and its rarity, urgent management actions are 30 needed to determine population size and trends in abundance in combination with fisher 31 education and awareness campaigns. 32 33 Key words: enforcement; euryhaline; conservation; protected species; river shark; threatened 34 species. 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 2 50 River sharks of the genus Glyphis (Carcharhiniformes: Carcharhinidae) are a group of highly 51 threatened, rare, and elusive sharks. Their distribution and status has been difficult to 52 determine, globally and locally, due to a lack of specimens, taxonomic and nomenclatural 53 issues, and occurrence in often remote, inaccessible or poorly-studied locations. Outside of 54 northern Australia, where intensive research is ongoing (e.g. Kyne, 2012; Feutry et al., 2014; 55 2017), these species are virtually unknown. 56 57 58 Prior to taxonomic resolution by Li et al. (2015), there were thought to be five species in the 59 genus Glyphis. However, molecular data confirmed that the Borneo river shark Glyphis 60 fowlerae Compagno, White & Cavanagh, 2010 from the Kinabatangan River, Sabah, 61 Malaysian Borneo, and the Irrawaddy river shark Glyphis siamensis (Müller & Henle, 1839) 62 from the Irrawaddy River, Myanmar, are junior synonyms of the Ganges shark Glyphis 63 gangeticus (Müller & Henle, 1839). As such, G. gangeticus has a widespread but patchy 64 distribution in the Indo-West Pacific. A further two species, the Speartooth shark Glyphis 65 glyphis (Müller & Henle, 1839) and the Northern river shark Glyphis garricki Compagno, 66 White & Last, 2008, occur across northern Australia (Pillans et al., 2010) and both were 67 recently rediscovered in Papua New Guinea (White et al., 2015). 68 69 70 River sharks are an evolutionarily unique group, specialized to inhabit large rivers and 71 estuaries. They are not however obligate freshwater species, but rather are euryhaline, relying 72 both on riverine and marine environments (Lucifora et al., 2015). Available data from 73 Australia suggest that juvenile Glyphis spp. inhabit tidally-influenced rivers, from low to 74 marine salinities, while adults are generally thought to occur in coastal and marine waters 3 75 (Pillans et al., 2010). However, adult specimens of river sharks are rarely encountered, 76 especially in the marine environment. The exception is G. garricki for which adults are 77 regularly recorded in riverine environments (Kyne, unpubl. data), while the first adult G. 78 glyphis were only recorded very recently, being taken from the coast of southern New Guinea 79 (White et al., 2015). 80 81 82 Records of G. gangeticus are patchy, mostly historical, and are often based on jaw material 83 only (Compagno et al., 2010; Li et al., 2015). In the Arabian Sea, the western extent of the 84 species’ range, there are records based on jaws prior to 2005, but the present status of the 85 species in this region is virtually unknown. The species’ conservation status is of 86 considerable concern (Compagno, 2007; Jabado et al., 2017). For example, recent targeted 87 surveys in its only known area of occurrence in Borneo, the Kinabatangan River, failed to 88 locate any records (Manjaji-Matsumoto et al., 2017). 89 90 91 As part of a study investigating shark landings along the northwestern coast of India (Gujarat 92 and Maharashtra states), data on shark landings were collected at the Sassoon Docks, a major 93 shark landing center located in Mumbai (Maharashtra) (Fig. 1). At this site, sampling was 94 carried out once a week from September 2014 to June 2016, between 6 and 8 am, to 95 investigate landings from gillnet boats, purse-seiners, and trawlers generally operating off the 96 coast of Maharashtra. 97 98 4 99 On 7 February 2016, a female G. gangeticus specimen was recorded measuring 266 cm total 100 length (LT) (stretched body). Identification was based on the following combination of 101 characters: broadly rounded short snout, small eyes, the absence of an interdorsal ridge, first 102 dorsal fin origin over rear third of pectoral base, second dorsal-fin height about half of first 103 dorsal-fin height, and an anal fin with deeply notched posterior margins, characteristic upper 104 teeth with high broad serrated triangular hooked cusps, and lower medials moderately large, 105 erect and hooked-cusped, narrowly symmetrical with arched roots with weakly serrated 106 cutting edges (Compagno et al., 2010; Ebert et al., 2013). While some photos were taken 107 (Fig. 2), additional information on the origin of the shark, detailed morphometric 108 measurements, and tissue samples for molecular analysis could not be collected due to rapid 109 processing by fishers and traders at the site. The specimen was most likely an adult, based on 110 its large size. 111 112 113 This G. gangeticus specimen represents the first confirmed record from across the species’ 114 range in over a decade, the first field observation of a whole large (and most certainly 115 mature) specimen, and the only record from the Arabian Sea outside of Pakistan. The last 116 available accounts of this species are from fishers and jaw traders in Pakistan (M. Harris and 117 G. Naylor, pers. comm.). These include six jaws collected in Karachi in 2001–2002, from 118 sharks estimated to be approximately 180–200 cm LT, as well as an additional set of jaws 119 collected from commercial gillnet landings at the Manora Basin in 2005, likely caught in 120 shallow coastal waters south of Karachi and around the Indus River mouth, and estimated to 121 be from a 275 cm LT shark (M. Harris, pers. comm.). 122 123 5 124 Information on the fishing location of this record is not available, and it is possible it could 125 have been caught anywhere along the northeast coast of the Arabian Sea. However, even 126 though records of this species are sparse, Glyphis species utilize rivers as nursery areas with 127 female philopatry demonstrated in G. glyphis (Feutry et al., 2017). It could be assumed that 128 the fishing vessel may have traversed north towards the Indus River (adjacent to Karachi, 129 Pakistan), an important site for the species in the northwestern Indian Ocean. However, 130 although the distribution and habitat preferences of adult river sharks remain a critical 131 knowledge gap, studies from Australia and Papua New Guinea indicate that adults can occur 132 outside of rivers in coastal marine environments (Pillans et al., 2010; White et al., 2015). In 133 fact, it is possible that adults may travel long distances with recent molecular data indicating 134 contemporary gene flow between the populations of G. gangeticus in Myanmar (= G. 135 siamensis), Borneo (= G. fowlerae), and those of India and Pakistan, suggesting marine 136 dispersal of several thousand kilometers (Li et al., 2015). 137 138 139 The historical population size of G.