9 Indian J. Fish., 64(4): 9-20, 2017 DOI: 10.21077/ijf.2017.64.4.63379-02 Reproductive biology and diet of the grey sharpnose shark Rhizoprionodon oligolinx Springer, 1964 (Chondrichthyes: Carcharhinidae) from the north-eastern Arabian Sea G. B. PURUSHOTTAMA, THAKURDAS, V. RAMASUBRAMANIAN * , GYANARANJAN DASH, K. V. AKHILESH, S. RAMKUMAR, SHOBA JOE KIZHAKUDAN, V. V. SINGH AND P. U. ZACHARIA ICAR-Central Marine Fisheries Research Institute, P. O. Box 1603, Ernakulam North, P. O., Kochi - 682 018 Kerala, India * ICAR-Central Institute of Fisheries Education (Deemed University), Panch Marg, Of Yari Road Versova, Andheri (W), Mumbai - 400 061, Maharashtra, India e-mail: puru44@gmail.com ABSTRACT Information on reproductive biology is presented for the grey sharpnose shark Rhizoprionodon oligolinx Springer, 1964 (Chondrichthyes: Carcharhiniformes), collected of the north-west coast of India in the Arabian Sea. A total of 711 individuals, of 27.0 to 93.0 cm total length (TL), 180 to 2600 g total weight (TW) were used for the study. The length- weight relationships were signifcantly diferent between the sexes. The size-at-maturity (Lm 50 ) for females and males was estimated to be 62.3 and 59.5 cm TL respectively. Number of embryos ranged from 1 to 7 and the size at birth was estimated between 25 to 30 cm TL. Overall sex ratio favoured the females slightly at the rate of 1.27:1. There was signifcant positive correlation between maternal TL and number of embryos (p<0.001). Dietary analysis of stomach contents (%IRI) revealed that R. oligolinx feeds primarily on teleosts (95.5%), cephalopods (3.2%) and crustaceans (1.2%). This study presents the frst detailed biological observation on size, sex composition, size-at-maturity (Lm 50 ) and length-weight relationship of R. oligolinx from the northern Arabian Sea. Keywords: Arabian Sea, Carcharhinidae, Diet, Embryo, Length-weight relationship, Reproductive biology, Size and sex compositions Introduction India is one of the major shark fshing nations of the world (Fowler et al., 2005; FAO, 2013; Dent and Clarke, 2015), having a long history of shark fshing by variety of crafts and gears in its subsistence, traditional small-scale fsheries and in commercial targeted fshery (Day, 1863, Bonfl, 1994; Hanfee, 1997, 1999; Kizhakudan et al., 2015). In 2014, estimated all India shark landings was 22479 t contributing 47.5% to all India elasmobranch landings (CMFRI, 2015) excluding those by illegal unreported and unregulated (IUU) catch. Even though sharks never formed a major component of traditional fshery in India contributing only 1% to the marine capture fshery, they support the livelihood of many fshers. Indian shark fshery moved from traditional, subsistence fshery or bycatch to high level targeted fshery over time (Hanfee, 1997; Hausfather, 2004). Though fshery is huge, biological studies on the major exploited species for creating better management plans are limited. Most of the sharks are highly vulnerable to overexploitation due to their biological characters and as a result world over there is a concern over this group. The present Indian fshery is witnessing a decline in the shark catch, which has created concern and there are several initiatives (e. g. fn attached policy in landing, banning the trade of shark fns, protection of vulnerable species and awareness programs) for their conservation and management (Kizhakkudan et al., 2015). Ebert et al. (2013) reported that of the 477 sharks worldwide, 45% (214) have been placed as Data Defcient under the IUCN Red List category, which hinders their management eforts. Currently India has a National Plan of Action for conservation and management of shark fsheries in India (NPOA) (BOBLME, 2015) and an advisory to NPOA by Kizhakudan et al. (2015). One of the major action plans in these reports were to identify gaps which limits management measures and improve studies on data limited vulnerable species. The genus Rhizoprionodon Whitley, 1929, commonly called requiem sharks, is distributed worldwide,