Limitations of DNA barcoding in determining the origin of smuggled seahorses and pipefishes

Seahorses and pipefishes are heavily exploited for use in Traditional Chinese Medicine (TCM), and less frequently for curio markets or as aquarium fish. A number of recent studies have used DNA barcoding to identify species sold at TCM markets in East Asia, but the usefulness of this approach in determining the region of origin remains poorly explored. Here, we generated DNA barcodes of dried seahorses and pipefishes destined for TCM that were confiscated at South Africa’s largest airport because they lacked the export permits required for the CITES-listed seahorses. These were compared with published sequences and new sequences generated for Mozambican seahorses, with the aim of determining whether it is possible to identify their country of origin. All pipefishes were identified as Syngnathoides biaculeatus, a widespread Indo-Pacific species, but the published sequence data did not provide sufficient resolution to identify the region of origin. The same was true of the majority of seahorses, which could not even be identified to species level because they clustered among an unresolved species complex whose sequences were published under the names Hippocampus kuda, H. fuscus and H. capensis. The presence of a few specimens of a second seahorse, H. camelopardalis, suggests that the shipment originated from East Africa because the range of this seahorse is centred around this region, but again, it was not possible to determine their country of origin. Even though seahorses and pipefishes have high levels of genetic population structure because of their low dispersal potential, DNA barcoding was only suitable to tentatively identify species, but not their region of origin. DNA barcoding is increasingly used to identify illegally traded wildlife, but our results show that more sophisticated methods are needed to monitor and police the trade in seahorses and pipefishes.