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

Abstract

Sharks and rays are at risk of extinction globally. This reflects low resilience to increasing fishing pressure, exacerbated by habitat loss, climate change, increasing value in a trade and inadequate information leading to limited conservation actions. Artisanal fisheries in the Bay of Bengal of Bangladesh contribute to the high levels of global fishing pressure on elasmobranchs. However, it is one of the most data-poor regions of the world, and the diversity, occurrence and conservation needs of elasmobranchs in this region have not been adequately assessed. This study evaluated elasmobranch diversity, species composition, catch and trade within the artisanal fisheries to address this critical knowledge gap. Findings show that elasmobranch diversity in Bangladesh has previously been underestimated. In this study, over 160000 individual elasmobranchs were recorded through landing site monitoring, comprising 88 species (30 sharks and 58 rays) within 20 families and 35 genera. Of these, 54 are globally threatened according to the IUCN Red List of Threatened Species, with ten species listed as Critically Endangered and 22 species listed as Endangered. Almost 98% juvenile catch (69–99% for different species) for large species sand a decline in numbers of large individuals were documented, indicating unsustainable fisheries. Several previously common species were rarely landed, indicating potential population declines. The catch pattern showed seasonality and, in some cases, gear specificity. Overall, Bangladesh was found to be a significant contributor to shark and ray catches and trade in the Bay of Bengal region. Effective monitoring was not observed at the landing sites or processing centres, despite 29 species of elasmobranchs being protected by law, many of which were frequently landed. On this basis, a series of recommendations were provided for improving the conservation status of the elasmobranchs in this region. These include the need for improved taxonomic research, enhanced monitoring of elasmobranch stocks, and the highest protection level for threatened taxa. Alongside political will, enhancing national capacity to manage and rebuild elasmobranch stocks, coordinated regional management measures are essential.

Vulnerability Assessment of Target Shrimps and Bycatch Species from Industrial Shrimp Trawl Fishery in the Bay of Bengal, Bangladesh

“…We found Himantura uarnak in the VU category of the global Red List [48], and in our PSA study, it showed low vulnerability (V = 1.56). The species is mainly exploited by artisanal fishing gear, i.e., modified drift gill nets, set bag nets, hooks, and long lines [8,59]. Harpadon nehereus, was listed as an NT species in the global Red List (IUCN, 2021), whereas it showed low vulnerability in our analysis (V = 1.25) and was largely caught by set bag nets, seine nets, and gill nets [60].…”

“…The weighted average data quality scores of productivity attributes and susceptibility attributes for the identified species fell under the moderate-low categories and moderate quality categories, respectively. Data on the life history traits and stock assessment of the identified species from the Bay of Bengal and adjacent waterbodies have not been adequately analyzed [8,56]. The majority of the data for productivity attributes were categorized as "very limited", and for susceptibility attributes, the majority of the data were categorized as "best" (Figure 3b) since the fishery-specific information was collected from the relevant sources of shrimp trawl fishery, alongside the current comprehensive state of the stocks in the Bay of Bengal, which had an impact on species' vulnerability analysis performed through the semi-quantitative approach [57,58].…”

“…The catch per unit fishing effort has been declining, and some species of marine shrimp and fish stocks are being depleted [5][6][7]. Consequently, the natural harmony of aquatic ecosystems has been disrupted by the over-exploitation of marine resources [8,9].…”

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

“…The latter provided flexibility to explore subjects important to individual respondents on an informal level, helping to characterize the system qualitatively. 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), ., and Haque, Cavanagh, and Seddon (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.…”

“…Sustainable elasmobranch fisheries are possible, and a number of developed countries manage some elasmobranch fisheries sustainably (e.g., School Shark, Galeorhinus galeus ; Gummy Shark, Mustelus antarcticus ; Alaskan Skate, Bathyraja parmifera in the USA and Australia) (Prince, 2005; Dulvy et al, 2017; Simpfendorfer & Dulvy, 2017). However, the sustainable management of these fisheries is underpinned by data, enabling effective monitoring and assessment, and a good understanding of the fishery, together with high levels of compliance to regulations (Prince, 2005; Dulvy et al, 2017; Simpfendorfer & Dulvy, 2017; Dulvy et al, 2021; Haque, Cavanagh, & Seddon, 2021). Despite initiatives such as the UN Food and Agricultural Organization (FAO) to develop sustainable management plans for elasmobranchs (https://www.fao.org/ipoa-sharks), many developing countries face challenges resulting from limited research and resources (e.g., Bornatowski et al, 2014; de Mitcheson et al, 2018; Haque et al, 2020; Haque, Cavanagh, & Seddon, 2021; Haque, D'Costa, et al, 2021; Haque, White, et al, 2021).…”