The lab, in collaboration with numerous colleagues, recently published a policy recommendation highlighting why the trade of Brown Frogs (Rana) towards the Republic of Korea is bad for biodiversity.
Background
The illegal trade in wildlife has introduced various species to new environments worldwide, including amphibians. Invasive species have harmful effects on local species through competition, predation, and other ecological interactions, including introducing non-native pathogens. Several species in the focus area of this study, including Rana huanrenensis, have been introduced to offshore islands in the Republic of Korea.
The Republic of Korea has a significant amphibian trade, including live animals for both pet trade and human consumption. The trade originates mainly from China and the USA and has grown significantly over the past two decades. As a result, some amphibian species have been designated as Alert Alien Species and invasive species, such as the American bullfrog, and have caused a severe loss of aquatic biodiversity. Eradicating invasive species is very complicated and expensive, making prevention of introduction the most cost-effective approach.
The Republic of Korea imports live Brown frog (Rana) individuals from China for human consumption, and this trade was conducted legally as some native species of the Republic of Korea can be legally traded. However, Rana uenoi, which is endemic to the Korean Peninsula and Tsushima Island in Japan after being split from the Rana dybowskii species complex cannot be legally traded anymore.
The Republic of Korea imports not only legally traded species but also non-native frog species that are morphologically similar to native ones, including Rana amurensis, Rana chensinensis, R. dybowskii, Rana kukunoris and Rana taihangensis. Once traded, some individuals may be released into nearby streams at the end of the legal sale period for welfare reasons, but this is a biosecurity threat because the frogs are not scanned for pathogens, and the African Swine Fever and Avian influenza pandemics have shown how quickly pathogens can spread. In addition, there is a threat of establishment, and hybridisation with local species.
International trade towards Korea requires updated regulations based on science-based recommendations to prevent the loss of biodiversity. Policy recommendations have the potential to help update national laws, especially in the case of the trade of invasive species. A policy recommendation on the trade of invasive American bullfrogs towards the Republic of Korea has coincided with a regulatory update in the trade of amphibians, but the discovery of non-native Rana species in the trade calls for additional updates in regulations. This policy recommendation has the potential to lead to further legal adjustments in the trade of the genus.
Risks of invasion
Amphibian trade can result in invasive species, causing two threats to the survival of native species. These threats include ecological interactions and pathogen dispersion, both of which have been documented in the invasive American bullfrog in the Republic of Korea. This species has impacted the ecology of native amphibians, reptiles, and birds, as well as increasing pathogen loads on native species.
Many Rana species have similar ecological requirements, and the impact of interactions between species pairs is unknown. Geographically distant clades of a single species may have significantly divergent ecological requirements, and displacement of individuals due to the introduction of non-native Rana species can result in competition and hybridisation, driving the extirpation of native Rana species. The negative effect of displacement can also be within a single species, resulting in individuals less adapted to the local environment or even species losses. Hybridisation can also magnify the invasive capacity of a species.
Rana species can transfer two major pathogens: Ranavirus and the chytrid fungus Batrachochytrium dendrobatidis (Bd). There have been mortality events occurring in both captive and wild populations in the Republic of Korea due to Ranavirus. Even if non-native Rana species have not been involved in these events, they pose a risk of escape from farms, and Ranavirus prevalence is higher in invasive Ranids in the Republic of Korea. Rana species can also be reservoirs for Bd, and the introduction of non-native Bd strains could have deadly effects. Therefore, the introduction of Rana species across natural boundaries can have disastrous consequences for local populations, including local extirpation.
The Republic of Korea’s Fourth National Biodiversity Strategy (2019-2023) contains action plans to address threats to biodiversity, including establishing mechanisms to control human-mediated species introduction and strengthening policy responses and post-introduction control of invasive species. The strategy also aims to protect endangered and endemic species and strengthen research and response to wildlife diseases, along with an improved wildlife rescue and care system. These actions are in compliance with legal obligations established by the Convention on Biological Diversity.
Current laws in the Republic of Korea allow for the import and captive breeding of certain Rana species with a permit, but measures are needed to prevent the introduction and establishment of non-native species that could harm native populations. Amphibians will soon be designated as aquatic organisms and regulated similarly to fishery products. Trade bans have already been implemented for some species in the Republic further strengthened.
Actionable recommendations
To prevent the introduction of new alien populations of Rana in the Republic of Korea, a ban on trading non-native Rana species should be implemented. This ban should also include domestic trade, specifically preventing the trade of R. uenoi from Jeju Island on the mainland. However, dead specimens of certain Rana species may be allowed for trade if it does not impact conservation efforts, and to prevent escapes and the release of pathogens.
To prevent the establishment of new invasive alien populations and the spread of pathogens, the release of any alien specimens and their offspring originating from past trade should be banned. Authorities should also use emergency measures to prevent the risk of population depletion, track and control potentially invasive species, and conduct broad-scale surveys for ranavirus and chytrid fungus. An updated National Species List that includes R. uenoi and a species identification key should be established to aid in border control and trade regulation efforts.
Conclusions
Non-native Rana species have been traded legally into the Republic of Korea, but regulations have not kept up with advances in taxonomy. While the establishment of alien Rana populations has not been confirmed, monitoring of populations and the presence of pathogens is necessary to prevent their establishment. The trade of non-native species for human consumption should be banned entirely, with the trade of native species limited to processed products and verifiable data to avoid the risk of invasion. The focus should be on Rana dybowskii, Rana amurensis, Rana chensinensis, Rana taihangensis, and Rana kukunoris, with additional analyses needed for conservation.
Laboratory of Animal Behaviour and Conservation 