Abstract
In recent decades, a combination of increasing demand and economic globalisation has created a global market for elasmobranch products, especially the highly prized shark fins for Asian markets. Morphological species identification, as well as traditional cytochrome c oxidase subunit I (COI) barcoding of shark fins and other products, become challenging when in a processed state (such as dried or bleached shark fins). Here a mini-barcoding multiplex assay was applied to determine the species of origin in case studies from southern Africa involving confiscated shark fins in different states of processing. This highlights that the illegal shark fin trade in southern Africa to a large extent comprises threatened species. Matching of sequences of the confiscated fins against public databases revealed several threatened species, including the CITES-listed species Carcharodon carcharias, Carcharhinus longimanus, Isurus oxyrinchus, Rhynchobatus djiddensis and Sphyrna lewini. The findings highlight the need for improved trade monitoring, such as to eliminate illegal trade in shark fins, which can in part be achieved through more widespread genetic sampling of internationally traded products. However, a major limitation to DNA barcoding in general lies in the lack of curated voucher specimens available on public databases. To facilitate the application of molecular methods in a more comprehensive evaluation of elasmobranch trade regionally, a concerted effort to create reliable curated sequence data is recommended.
Highlights
Over the past few decades there has been overexploitation of sharks on a global scale, primarily to supply international markets with products such as meat, skin, fins, cartilage, liver and teeth (Clarke et al 2006; Lack and Sant 2009; Dulvy et al 2014)
In the first case study of shark fins confiscated by the Mozambique Customs Authority in Maputo, Mozambique, all 89 samples tested amplified for either the 150-bp or the 200-bp c oxidase subunit I (COI) gene region
Based on sequences from the 150-bp and 200-bp COI gene regions, 65 samples were unambiguously identified to species level and consisted of 13 different elasmobranch species (Figure 2), with all these samples showing a species match of >98%
Summary
Over the past few decades there has been overexploitation of sharks on a global scale, primarily to supply international markets with products such as meat, skin, fins, cartilage, liver and teeth (Clarke et al 2006; Lack and Sant 2009; Dulvy et al 2014). The main species targeted for the shark fin industry include blue shark Prionace glauca, shortfin mako shark Isurus oxyrinchus, silky shark Carcharhinus falciformis, dusky shark C. obscurus, sandbar shark C. plumbeus, tiger shark Galeocerdo cuvier, bull shark C. leucas, scalloped, smooth and great hammerhead sharks Sphyrna lewini, S. zygaena and S. mokarran, common, bigeye and pelagic thresher sharks Alopias vulpinus, A. superciliosus and A. pelagicus, oceanic whitetip shark C. longimanus, and more recently shark-like rays of the families Rhinidae (wedgefishes) and Rhinobatidae (guitarfishes) (Amaral et al 2017; Fields et al 2018) These species are targeted directly or caught as incidental bycatch (Worm et al 2013; Oliver et al 2015) and used to supply a market that is largely unmonitored and unregulated. More than half of the chondrichthyans that enter the fin trade are under threat (Dulvy et al 2014)
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