Discovering the historical routes and networks that determined the global export of tortoiseshell in the nineteenth and twentieth centuries reveals that at least six times more turtles were slaughtered than previously thought.
Tracking the movement of the turtle products, say researchers led by Emily Miller of the Monterey Bay Aquarium in California, US, results in a more accurate picture of the exploitation of the endangered hawksbill sea turtle (Eretmochelys imbricate).
Because many of the networks discovered are still in use, the work also serves to illuminate the ongoing illegal, unregulated and unreported fish trade, which is putting several species at risk of extinction.
Evidence suggests that turtle carapaces, turned into a range of decorative or functional artefacts, have been traded for millennia.
Traditionally, Japan was the cultural and geographic centre of the enterprise. Miller and colleagues opted to begin their research at 1844, when the modern global tortoiseshell trade began in earnest, with networks spreading from Japan across the Pacific.
The trade then spread to the Indian basin in 1863 and the Atlantic basin in 1882.
Centralised records in Japan began with the formation of a customs archive in 1868. They reveal that sales activity dipped to negligible levels at the outset of World War II, a situation which continued through the period of US occupation before peaking again in the 1970s.
In 1977 the Convention on International Trade of Endangered Species of Wild Fauna and Flora (CITES) banned sales in hawksbill products, but Japan and several other countries, including Fiji and Vietnam, did not acknowledge the prohibition for several years.
Today, the legal international trade has almost entirely ceased. However, Miller and colleagues report, “legal domestic exploitation in several countries and tortoiseshell trafficking exist”.
Hawksbills are critically endangered, with only around 25,000 breeding age females remaining across the entire range. Research shows the turtles are rarely killed as bycatch from fishing operations, because they spend little time in deep water.
“Instead,” the authors write, “hawksbill turtles have been directly targeted and may be the most heavily exploited sea turtle species. Direct exploitation is thought to be the major driver of their decline.”
A previous study, prepared for the International Union for Conservation of Nature, produced figures for the tortoiseshell trade between 1950 and 1992. During that period, an estimated 1.4 million turtles were killed, although the accuracy of the figure is constrained by data quality and interpretation.
In particular, data was based on the assumption that only mature male turtles were taken for the trade. Miller and colleagues produce different, and perhaps more realistic, models factoring in several other scenarios, including the killing of females and juveniles. They also model turtle catch as an artefact of “fishing down” – the process by which species are progressively added to commercial hauls as initial target species decrease in number.
This recalibration, plus extending the research period to cover 150 years, produced alarming totals, suggesting that earlier estimates were very much on the light side.
“Globally, at least 4,640,062 individuals were exploited under the large adults scenario, 5,122,951 individuals under the mixed adults scenario, 9,834,837 individuals under the mixed ages scenario, and 8,976,503 under the fishing down scenario,” the authors report.
And while the CITES ban continues to be enforced, the prognosis for hawksbill turtles remains dire. Miller and colleagues report that China has lately emerged as a significant exporter of tortoise shells, and that smuggled and deliberately mislabelled tortoiseshell represents a hefty portion of black market operations in Vietnam and the Philippines.
The historical research, conclude Miller and colleagues, provides a useful resource for tracing current turtle smuggling routes, even though some pathways have changed over time. It also holds potential for investigators trying to track down on forms of wildlife exploitation.
“The strong links between IUU fishing and marine wildlife poaching and trafficking underscore the need for integrated monitoring and management of small-scale coastal fisheries and high-seas commercial fleets,” they write.
“Success here may benefit the continued persistence of endangered marine wildlife and reduce human rights abuses, and drug, weapon, and other illegal trade also associated with these networks.”
The research is published in journal Science Advances.
