Saturday, November 22, 2014

A large sea snake harvest that has gone unnoticed for a decade

Conservation of sea snakes is virtually nonexistent in Asia, and its role in human–snake interactions in terms of catch, trade, and snakebites as an occupational hazard is mostly unexplored. In a recent paper in Biological Conservation Nyguen et al (2014) report data on sea snake landings from the Gulf of Thailand, a hotspot for sea snake harvest by squid fishers operating out of the ports of Song Doc and Khanh Hoi, Ca Mau Province, Vietnam. The information was collected during documentation of the steps of the trading process and through interviewers with participants in the trade. Squid vessels return to their ports once per lunar synodic cycle and fishers sell snakes to merchants who sort, package, and ship the snakes to various destinations in Vietnam and China for human consumption. They are also used as a source of traditional remedies. Annually, 82 tons, roughly equal to 225,500 individual snakes, of live sea snakes are brought to ports. Knowledge of the harvest has been largely ignored and the rate of harvest constitutes one of the largest venomous snake and marine reptile harvest activities in the world today. In the harvest two species, Lapemis curtus and Hydrophis cyanocinctus, constituted about 85% of the snake biomass, and Acalyptophis peronii, Aipysurus eydouxii, Hydrophis atriceps, H. belcheri, H. lamberti, and H. ornatus made up the remainder. The results of this new paper establish a quantitative baseline for characteristics of catch, trade, and uses of sea snakes. Other key observations include the timing of the trade to the lunar cycle, a decline of sea snakes harvested over the study period (approximately 30% decline in mass over 4 years), and the treatment of sea snake bites with rhinoceros horn. Emerging markets in Southeast Asia drive the harvest of venomous sea snakes in the Gulf of Thailand and sea snake bites present a potentially lethal occupational hazard.

The authors suggest that the Gulf of Thailand/southern Vietnam is one of the largest harvests of venomous snake and marine reptiles in the world. Yet sea snakes are not even mentioned in studies concerning reptile exploitation in Asia or globally. This underreported status is particularly notable given that the Indonesian archipelago has the highest marine species diversity in general and specifically is among the areas ranked as having the greatest richness of sea snake species on Earth. Still, in this area an unexplained decline of sea snakes has been reported. The eight commercially traded sea snake species reported on represent a significant proportion of the 20 species known in the Gulf of Thailand and of the 25 species known from Vietnam, including the South China Sea.
Globally, 9% of sea snakes are threatened, 6% are near threatened, and 34% are data deficient, as defined by the International Union for the Conservation of Nature (IUCN). The species in this study, as well as all other species known from the Gulf of Thailand, are currently categorized as either least concern or data deficient. However, the results suggest that in the Gulf of Thailand a large subset of the sea snake species now considered as least concern or data deficient may, in fact, be in danger of having their populations damaged or destroyed through over harvesting. According to the results presented in this paper, the number of sea snakes harvested from the Gulf of Thailand by boats based at the study sites was 6.35 specimens per square kilometer per year. The authors could not exclude the possibility that sea snake species in addition to those observed were traded from other harvesting grounds (e.g., harvest landing in Vung Tau, Vietnam). The volume of harvested sea snakes documented is a conservative estimate of the total harvest from the Gulf of Thailand. It is very likely that more snakes were harvested by squid vessels and trawlers that originated from ports in Malaysia and Thailand. Sea snakes have been brought into the ports of Songkhla, Thailand, Kra Isthmus, Thailand, and Endau, Malaysia. Sea snake harvests similar to the one reported here could be occurring in (or spread to) other areas of the South China Sea and wider Southeast Asia. Ten years ago in Quảng Ng˜ai, the sea snake bycatch was discarded due to fear of bites and a lack of market; however, in 2011 their price was US$10–35/kg. Knowledge of the biology of sea snakes and their role in the ecosystem is limited. Thus, understanding of the effect that this harvest may have on populations or on the wider ecosystem is limited. The results supply evidence that the mass of snakes harvested from the Gulf of Thailand has been decreasing since 2009, and fishers interviewed consistently reported a decline since they first began capturing sea snakes as a commodity.

Snake bites during the trade process are occupational hazards that carry a high risk given the lethal venoms and lack of availability of antivenin therapy. The economic incentive of harvesting sea snakes, from the fishers’ and merchants’ perspectives, clearly outweighs the snake bite risk. With respect to fatalities the authors report, one affected family continued trading in sea snakes, while another family terminated participation in the snake trade.

The authenticity and effectiveness of rhinoceros horn and other locally used remedies for snake bites remains unproven. Yet, use of rhinoceros body parts in Vietnam has been directly linked to poaching of rhinoceros in South Africa. The observation suggests a link between rhinoceros poaching and sea snake harvest in the Gulf of Thailand. Both fishers and merchants take advantage of emerging market opportunities. According to the merchants, government, and nongovernmental officials interviewed, the large-scale harvest of sea snakes from the Gulf of Thailand is tied to economic prosperity and thus increase demand domestically in Vietnam and from China for snake products. The demand is due to the perceived health benefits of sea snakes and consumption of sea snakes as status
Items. This particular sea snake harvest has been going on essentially unnoticed by national and international conservation organizations for more than a decade, in part because it apparently does not overtly conflict with Vietnamese laws. Yet, given the volume of snakes and the wide spectrum of species extracted and that the environmental effects of the harvest are unknown, immediate attention by conservation organizations to sea snake harvesting appears warranted. Ironically, the enforcement of laws aimed at managing the trade in widely harvested terrestrial snakes, such as various cobra species (e.g., Naja spp., Ophiophagus hannah), may have the unintended consequence of increasing the market for sea snakes.


Nguyen C, Nguyen TT, Moore A, Montoya A, Rasmussen AR Broad K, Voris HK, Takacs Z. 2014. Sea Snake Harvest in the Gulf of Thailand. Conservation Biology 28: 1677-1687.

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