Vol. 40: 65–73, 2019 ENDANGERED SPECIES RESEARCH Published October 17 https://doi.org/10.3354/esr00981 Endang Species Res OPENPEN ACCESSCCESS New records of the Critically Endangered Ganges shark Glyphis gangeticus in Bangladeshi waters: urgent monitoring needed Alifa Bintha Haque1,2,*, Sudipta Arka Das3 1Department of Zoology, University of Dhaka, Dhaka 1000, Bangladesh 2Department of Zoology, University of Oxford, 11a Mansfield Rd, Oxford OX1 3SZ, UK 3Department of Biochemistry and Molecular Biology, University of Dhaka, Dhaka 1000, Bangladesh ABSTRACT: The different species of elasmobranch found in Bangladeshi fisheries and markets were quantified in a survey between February 2016 and November 2017. This resulted in records of the Critically Endangered Ganges shark Glyphis gangeticus (Müller & Henle, 1839) in the waters of Bangladesh. Three records from the landing sites and shark processing centres of Cox’s Bazar in southeast Bangladesh were identified and confirmed as G. gangeticus by sequencing the expression of the cytochrome c oxidase subunit I (COI) gene and by the morphological identifica- tion of 1 individual. These represent the most recent records of this species in Bangladesh in over a decade, and only the second set of records from anywhere within the range of this elusive shark. Capture dates and traders’ knowledge of these catches suggest a year-round distribution, indica- ting a population within the Bay of Bengal and adjacent coastal rivers. Although the species is pro- tected under Bangladeshi law, enforcement of the law is inadequate. Monitoring for this, and other, rare and threatened species at landing sites, rigorous surveys to locate any existing popula- tions, trade regulation, and enforcement of conservation legislation should be considered priori- ties for effective conservation. KEY WORDS: Bay of Bengal · Marine conservation · DNA barcoding · Distribution · Elasmo- branch · Elusive river shark 1. INTRODUCTION sharks, one of the most enigmatic groups of sharks in the world (Li et al. 2015, White et al. 2015). However, The Bay of Bengal harbors a rich community of there is a paucity of information on their specific dis- marine animals (Amaral et al. 2017). However, little tribution in the coastal areas and tropical rivers. is known about the elasmobranchs (sharks and rays) Three species of river shark have been reported in in this region (Hoq et al. 2011) owing to a lack of spe- Bangladesh, 2 of which have been described (Glyphis cies-specific research regarding their ecology, biol- glyphis and G. gangeticus; Roberts 2006, Hoq et al. ogy, habitat, trade and species composition (Fischer 2011), and one of which is still undescribed and et al. 2012). Moreover, the world’s largest halophytic genetically distinct (Li et al. 2015, Amaral et al. 2017). mangrove forest, the Sundarbans Reserve Forest This undescribed species, overlapping in its distribu- (SRF), is located in the west of the Bay of Bengal and tion with G. gangeticus (Amaral et al. 2017), is only is a cradle for many unique species (Gopal & Chau- known to be found in the Gangetic delta (Pal et al. han 2006), including threatened and evolutionary 2014). Within the western Indo-Pacific, the Ganges distinct species. This is a suitable habitat for river shark (G. gangeticus) has a widespread but patchy © The authors 2019. Open Access under Creative Commons by *Corresponding author: [email protected] Attribution Licence. Use, distribution and reproduction are un - restricted. Authors and original publication must be credited. Publisher: Inter-Research · www.int-res.com 66 Endang Species Res 40: 65–73, 2019 distribution (Jabado et al. 2018) (Table 1). Identifica- re ported in 2006 (Roberts 2006) from Bangladesh. tion is based primarily on the jaws because whole Inconsistent monitoring resulted in long intervals individuals have rarely been found and examined. between encounters. Hence, monitoring such rare Previously believed to be restricted to freshwater in and threatened species requires multiple methods, the Ganges, this species is predominantly euryhaline, including market and landing observations, evaluat- with marine records documented by Roberts (2006). ing ecological knowledge of fishers and traders, G. gangeticus is characterized by conflicting in - habitat surveys, and the use of molecular techniques formation spanning from the early 1800s to recent such as DNA barcoding. studies. Information varies from it being designated Two pieces of regional legislation protect endan- as a species endemic to the freshwater of the Ganges gered species in the Bay of Bengal and apply to G. to it being a man-eater (Roberts 2006). While it was gangeticus. Since 2001, G. gangeticus has been mentioned to have been the ‘most common’ ground protected under Schedule I, Part II A of the Indian shark species in the Bay of Bengal (Roberts 2006), it Wildlife (Protection) Act, 1972, and also under is also designated as Critically Endangered by the Schedule I of the Wildlife (Conservation and Secu- IUCN Red List of Threatened Species (Compagno rity) Act, 2012, in Bangladesh. The effectiveness of 2007), mainly because of the continued decline of these regulative measures is limited, for the fol- mature individuals, its restricted range, overfishing, lowing reasons. Firstly, effective elasmobranch increased human use of rivers, pollution and habitat landing monitoring programs run by government degradation (Compagno 1997). Moreover, it is only agencies are either absent altogether or highly known historically from museum specimens (Com- faulty. This leads to limited knowledge of threat- pagno 2007), where cryptic similarities to other spe- ened and data deficient species. Secondly, there is cies and lack of specimen data pose great challenges a lack of awareness among fisherfolk and traders to accurate morphological identification. Prior to the about the law and what they should do with pro- taxonomic resolution by Li et al. (2015), G. siamensis tected species. The present study thus aimed to and G. fowlerae were considered to be synonymous monitor the largest landing site for marine fish, to G. gangeticus, further complicating the identifica- Cox’s Bazar, Bangladesh, for 3 mo following the tion process. discovery of G. gangeticus among the elasmo- After it was first described in 1839, the species branch products traded there. was not recorded between 1867 and 1996, with the The present study provides an initial understand- 1996 record being unconfirmed (Compagno 2007). ing of the landing patterns of rare and threatened However, several specimens of Ganges sharks were elasmobranch species in Bangladesh and identifies Table 1. Summary of historical and recent records of Glyphis gangeticus showing patchy encounter rates after long intervals. TL: total length; –: not known Specimen No. of Location of Time of Reference Notes specimens collection collection Historical samples 3 Lower reaches of the 19th Compagno (1997), Preserved in museums of G. gangeticus Ganges-Hooghly century Roberts (2006) in Paris, Berlin, and India freshwater river system G. gangeticus − Ganges River 1996 Compagno (2007) After searching for 10 yr Further confirmation Upstream of Hooghly − Compagno et al. By a photograph of the jaw of G. gangeticus − River, at Mahishadal (2008) More recent Several Lower Sundarbans, 2006 Roberts (2006) Identified as a common encounter south of Khulna, shark, contrary to of G. gangeticus Bangladesh existing beliefs First record of 1 Mumbai, India Feb Jabado et al. (2018) Female, 266 cm TL G. gangeticus in 2016 the Arabian Sea First record of 3 Cox’s Bazar, Feb−Nov Present study Male, 118.11 cm TL G. gangeticus in Bangladesh, 2017 (1 of the 3 specimens) Bangladesh after Bay of Bengal more than a decade Haque & Das: Ganges shark in Bangladesh 67 challenges for their conservation. It includes the 2.3. Informal interviews very first records of G. gangeticus from Bangladeshi waters since 2006. It also tests the usefulness of To quantify local knowledge of native carcharhinid incorporating local knowledge on trade, seasonality, sharks, the fishers and traders were asked to partici- and perceptions of sharks and shark conservation pate in a brief informal interview following the ex - legislation. traction of DNA samples. The interviewees were shown photographs of several species from the order Carcharhiniformes (e.g. Ganges shark, pig eye shark, 2. MATERIALS AND METHODS bull shark, tiger shark, silky shark, spot-tail shark, scalloped hammerhead and winghead shark) to de - 2.1. Sampling site, genetic sampling and analysis termine whether locals are able to differentiate them. Cox’s Bazar was chosen as a sampling site as it is the largest landing site for marine fish by volume 3. RESULTS and is a trade hub for elasmobranchs in southeast Bangladesh. The shark landing site (n = 1) and pro- 3.1. Morphological identification cessing centres (n = 6) in Cox’s Bazar were visited twice a month (Fig. 1) between February 2016 and On 13 November 2017, a whole specimen of Gly - November 2017. Morphological data on all landed phis gangeticus (S1) was identified from the Bang la - whole elasmobranch species and 20−30 tissue sam- desh Fisheries Development Corporation (BFDC) ples of meat, fin, and muscle from jaws and skin landing site, Cox’s Bazar (Fig. 1). The identification of were collected randomly from the landing site. the specimen (Fig. 2A,B) was based on the combina- Where it was possible to differentiate individuals tion of the characteristics described in Compagno and individual