Fishing and trade of devil rays (Mobula spp.) in the Bay of Bengal, Bangladesh: Insights from fishers’ knowledge

Abstract

Devil rays (Mobula spp.) are globally threatened cartilaginous fishes that have attracted global conservation concern owing to their high extinction risk and lack of protection in many countries. Limited resources and data on threatened marine species, including devil rays, impede conservation actions, particularly in developing countries, many of which have high biodiversity. Devil ray catch is a component of artisanal fisheries in Bangladesh, but data on their fisheries and trade are limited. To characterize devil ray fishing practices, fishers’ perception and trade, 230 fishers and traders were interviewed between 4 June 2018 and 22 June 2019, in four areas of south‐east Bangladesh. Catch data were also opportunistically collected at landing sites. Six devil ray species were documented, caught in an array of gill nets, set‐bag nets and longlines. All interviewed fishers reported life‐long devil ray bycatch in some numbers, and also noted a decline in catch over the last decade. Bottom trawling, increased bycatch levels, increased demand for devil ray products and, in some cases, ecosystem changes were identified by fishers as threats to devil ray populations. Unregulated and undocumented trade and retained bycatch, especially by gill nets and set‐bag nets, are fuelled by local consumption of devil ray meat and international trade in meat and gill rakers. Compliance with international trade control treaties for all Mobula spp. or the Bangladeshi law protecting Mobula mobular was low, with the majority of fishers (87%, n = 174) unaware of their existence. To manage devil ray fisheries, and prevent possible population declines, we propose a combination of legally enforced gear modifications, and catch and trade control through community‐owned implementation strategies. Additionally, we propose the simultaneous implementation of inclusive, community‐based awareness and stewardship projects in conjunction with a coast‐wide ray monitoring programme. Finally, we emphasize that more research and action rooted in a sustainable fishery model is urgently needed to protect Bangladeshi devil ray populations.

Evaluating artisanal fishing of globally threatened sharks and rays in the Bay of Bengal, Bangladesh

“…A ~50% decline is reported in the elasmobranch catch rate between 1978–80 and 2013 [ 115 ], with an increase in catch of smaller short-lives species compared to larger long-lived ones, indicating overexploitation of the elasmobranch populations [ 116 , 117 ]. Similar patterns are evident in Bangladesh, where fishing efforts has increased more than 1300 times in the last 60 years [ 90 ] and abundant catch of short-lived species. The decline is confirmed by steep depletion in biomass of elasmobranchs, as well as the average size, number and diversity of the animals landed (Haque in prep.)…”

“…zijsron ), were recorded. However, the sawfish records were presented and discussed separately [ 27 , 90 ].…”

“…The fishing effort in Bangladesh increased from 420 to 582670 kW overall between 1950 and 2014 [ 70 ]. The effort increased four-fold between 2000 and 2014 [ 41 , 90 ]. Studies have shown, the average landings of elasmobranch have declined from the 1990s [ 41 , 70 ] with a reduction in the composition, size and number of elasmobranchs in Bangladeshi waters.…”

“…Traders and workers in the centres were asked to differentiate amongst the landings to avoid double counting any specimens. Although the presence of largetooth and green sawfish has been presented and discussed in other studies [ 27 , 90 ], this record has been incorporated here for a complete understanding of species composition in artisanal catch and diversity.…”

Fishers' tales—Impact of artisanal fisheries on threatened sharks and rays in the Bay of Bengal, Bangladesh

“…Stakeholder‐specific semi‐structured questionnaires to evaluate: (1) fishing practices; (2) target and by‐caught species and their value; (3) legal frameworks governing fishing activities and compliance to these; and (4) the attitude of fishers toward conservation measures were designed partially based on Jabado et al (2015), Jaiteh, Loneragan, and Warren (2017). , and Haque, Cavanagh, and Seddon (2021); Haque, D'Costa, et al (2021). In some instances, related questions were grouped together (e.g., questions regarding the value or species) to aid both the information gathering and analysis.…”