Socio-ecological approach on the fishing and trade of rhino rays (Elasmobranchii: Rhinopristiformes) for their biological conservation in the Bay of Bengal, Bangladesh

Abstract Rhinopristioid rays are among the most globally threatened cartilaginous fishes, almost all of which are Critically Endangered. Fishery pressure and lack of knowledge, especially where these elasmobranch fish overlap their habitats off developing countries in the Indo-West Pacific, impede their biological conservation which in turns result in unnoticed population depletion. Rhino rays are an important component of the Bangladeshi artisanal fishery; however, an understanding of these fisheries and their trade is limited. Fishers and traders were interviewed between June 2018 and June 2019 in four areas of southeast Bangladesh to characterize rhino ray fishing, trade and fishers' perception of population trends. All interviewed fishers reported life-long rhino ray catch in sizable numbers and noted a steep decline in the catch over time, especially for Rhynchobatus spp. Seven species were documented- not only targeted by un-baited longlines but also by-caught in gillnets and set-bag nets. Unregulated and undocumented catch fuelled by substantial international trade to Myanmar on high-quality skin, meat and fins; and national usages of meat, liver, cartilages and intestines. Between 9000 and 33000 kg (avg. 23000 kg) of rhino rays were bought annually by each trader during 2015–2018. Southcentral shallow-water char (sand island) areas are perceived as essential habitats, hence providing important fishing grounds. The predominant threats are overexploitation by unselective gear use, bottom trawling, target catch, international trade and source of protein and income. Compliance with international trade control treaties or the Bangladeshi law was low, with most fishers (78%) unaware of specific regulation regarding rhino rays. It is crucial to adopt precautionary principles to prevent further rhino ray population declines. We propose a combination of actions rooted in sustainability and inclusiveness in this regard; e.g. a) trade mitigation, monitoring and enforcement, b) need for sustainable fisheries management regimes, c) need for habitat protection; finally, d) the importance of fishers’ inclusiveness in conservation decision making.