This study is the first genetic identification of shark fins commodity in Thailand. The number of assessed shark fins is quite low compared to the number of fins being traded because market accesses were limited; however, we identified 13 shark species of which two are CITES regulated. A large portion of the samples were sharks that cannot be found in Thai waters. The native distribution of C. signatus and M. schmitti are in the Atlantic Ocean. The spiny dogfish, S. acanthias has a wide distribution range but there is no report from Thailand and adjacent countries (www.fishbase.org). This finding is concordant with the trade records obtained from The Customs Department in Thailand, where shark fin products (HS-03039200 and HS-03057100) are imported from many countries such as Argentina, Norway, United States, Indonesia, Singapore, China and Taiwan (The Customs Department 2021). The geographical origin of shark fins in Thailand’s market is hard to trace due to the obscure nature of the trade of this lucrative and occasionally illegal product, where re-export is also common in many countries before being imported into Thailand and commodity coding revisions from The Customs Department (Dent and Clarke 2015). A large proportion of shark species recorded in Thailand for this study could not be determined that they were captured in Thai waters since some species are widespread (Dulvy et al. 2014). Moreover, the large percentage of shark species that occur outside of Thai waters provides evidence that the fins traded in Thai markets rely heavily on sources from outside the country, which maybe imported to satisfy the local demand or re-export as a trading hub. Lack of traceability shark fin trade and the interlink of source and sink for globally threatened species are still a barrier to understand the trade route of shark fin in Thailand. The traceability system should be established both domestically and internationally.
Over half of species reported in this study are listed under threatened categories listed in IUCN Red List and Thailand Red data. There are 6 Critically Endangered species, 16 Endangered species and 22 Vulnerable species of sharks that can be found in Thai water listed in IUCN Red List (Krajangdara 2021). Two Critically Endangered species, 2 Endangered species and 5 Vulnerable species from the IUCN Red List are presented in this study. The record of these 9 species reveals utilization of threatened species of Thailand in fin trade. The highest proportion of C. sorrah infer to the large volume of this species being exploited to support Thailand’s small low-value shark fins market. This species is one of the dominant shark species in Thai fisheries (Krajangdara 2021) and is frequently captured in Southeast Asia (Fahmi. and Sumadhiharga 2007; Moore et al. 2012) and Southwest coast of India (Akhilesh et al. 2011). The C. sorrah is classified as Vulnerable in Thailand Red data, but their status is Near Threatened listed in IUCN Red List (Krajangdara et al. 2019). The recent status on IUCN Red List of this species is based on the biological data of Australian samples (Giles et al. 2014). Its status listed in IUCN Red List should be revised due to the prevalence of the species in the marketplace. Moreover, the stock of C. sorrah should be assessed for each regions for fisheries management since there is genetic variation in C. sorrah populations across Indo–West Pacific region (Giles et al. 2014) and its landings were dominated by immature size in Southeast Asia (Fahmi. and Sumadhiharga 2007; Moore et al. 2012). Two species listed in CITES appendix were found among the samples and many Critical Endangered species from IUCN Red List were detected, highlighting the utilization of these species in the global shark fin trade, while there is currently no law to prohibit capturing them in Thailand. Monitoring of this particular species should be prioritized to understand their conservation status and sources of fin trade.
Threatened species are recorded in all locations except Pattani. Various proportion of all threatened categories found in samples collected from Bangkok and vicinity reflect that it is the center of Thailand’s shark fin market which obtains product from many sources, while the markets outside of Bangkok probably obtain shark fin products from the local sources or one of dealers in Bangkok and vicinity. Moreover, it was noted that our surveys around out of town markets were done during COVID-19 pandemic when most of the shops were closed due to low number of travelers. The types of sample sources are limited, which might fail to detect some other species present in fins trade in Thai market, however the record of threatened species from each location presents useful information for further investigation.
Many samples from the species that are classified as Critical Endangered, Endangered, and Vulnerable were found in small size class. The fins commonly marketed and exported from Thailand are small low-value fins (Dent and Clarke 2015) which results in being the majority size class of fin samples collected in this study. The species that were only detected in small size class of fin samples are Carcharhinus obscurus, Carcharhinus plumbeus, Loxodon macrorhinus, Rhizoprionodon spp., Triaenodon obesus, Sphyrna spp., M. schmitti, Chiloscyllium punctatum, Chiloscyllium sp. and S. acanthias, however most species reported in this study can be also found in the small size class. It was difficult to determine maturity of sharks from shark fins alone since there is limited information on the relationships between fin length and size at maturity of different shark species. However, we considered that all small size samples, except smaller sharks Chiloscyllium spp. and S. acanthias, are immature because it was estimated that the most commonly traded fins i.e. dorsal, pectoral or caudal fin of many mature shark species such as C. brevipinna, C. plumbeus, C. limbatus, C. sorrah, C. amboinensis etc. are larger than 10 cm (Al-Qasmi 1994; Oktaviyani et al. 2020). We could not accurately determine which fin type our sample consisted of, however, the small size of fin samples in this study are considerably smaller than all fin types of mature sharks in general (Al-Qasmi 1994; Oktaviyani et al. 2020). Harvesting immature sharks can affect the recruitment process of shark population, and hinder the recovery potential of the stock from exploitation (Fahmi. and Sumadhiharga 2007). This finding should raise awareness to shark management policymakers and consumers. Study of relationships between fin length and mature size of shark will indicate the minimum size of shark fins that should be allowed in the trade for sustainable fishery in the case that the fisheries was targeted for sharks. However, given the critical status of shark species globally, the consumed shark fins could be globally threatened and illegal. Traceability of shark fin trade should be mandated.
The quality of DNA template directly affects the success rate of amplification in PCR. In case of shark fin product in this study, the range of DNA quality from excellent to bad condition that yield from different types of fins can be found. Frozen fins which are generally well-preserved in cold storage and dried fins which are chemically untreated provide higher success rate of amplification. Processed dried fins and processed wet fins should be avoided from further sample collection for this kind of study since it was difficult to get optimum amplification results. Effective approach modified from Cardenosa et al. (2017) and Fields et al. (2015) were applied to utilize when various quality of DNA template was an obstacle. We presented a protocol for sequencing analysis which was suitable for a wide range of sequence length and quality. Any sequences that hold less than a 100% match of the query sequence but it show high percent similarity to the reference database imply to intra or inter-specific variation (Wong et al. 2009), so define the lowest scientific name as generic name will eliminate wrong species identification from sequencing analysis. Lower query cover sequence which is 80-100% identical to species level in data base should not be disregarded since it can provide unspecifically acceptable levels such as generic name of unknown sample. Screening of species composition via COI gene is generally acceptable and applicable worldwide (Ward et al. 2005; Bhattacharya et al. 2016; Bingpeng et al. 2018), however, using two or more markers is more preferable to generate more accuracy in taxonomic examination (Domingues et al. 2021), such as NADH dehydrogenase subunit 2 (NADH2), which is especially useful for accurate identification of sharks of the genus Mustelus (White and Last 2012; Marchetti et al. 2020). Nonetheless, our protocol is another option for fast and low-cost analysis when many genes analysis is quite impossible.
This study emphasizes conservation concerns, particularly for the large volume of elasmobranchs categorized as Critical Endangered assessed by the IUCN Shark Specialist Group. In addition, the majority Vulnerable and Endangered species identified from shark fin product indicated that we need more law enforcement and trade monitoring for those threatened species before their populations decline even further. Species identification using external morphological examination can be a first step to identify CITES-listed species or regulated species (Marshall and Barone 2016), however, missing key diagnostic characteristics of processed fin or even in dried fins remains problematic (Ferrette et al. 2019; Villate-Moreno et al. 2021), therefore we recommend DNA-based identification methods to detect threatened species and CITES-listed species in shark fin trade. A standard molecular diagnostic technique is another step to enhance species identification accuracy (Van Houtan et al. 2020; Villate‐Moreno et al. 2021). This approach is also more convenient for the trade monitoring staffs since it does not require extensive training in taxonomy, which is especially in shortage in Thailand and DNA based approach can be performed by outsources. DoF should be empowered and equipped with all necessary resources to be able to fulfil CITES obligation. This should be prioritized in Thailand's NPOA-Sharks. A random molecular test of subsamples of shark products in regular period will provide invaluable information for future evaluations for the threatened and CITES listed species, aid in better management for shark resources in this region, and also help in enforcement on the trades of illegal shark species within Thailand as one of the hub of fins trade in the world.