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Articles

Diadromy in a large tropical river, the Mekong: more common than assumed, with greater implications for management

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Pages 38-50 | Received 18 Dec 2019, Accepted 24 Aug 2020, Published online: 29 Sep 2020

Abstract

Diadromous fishes, those that migrate between fresh and marine waters, are among the most vulnerable species to river infrastructural development. These fish need to move between fresh water and the sea, so any obstruction to migration can block access to critical habitat areas. The Lower Mekong Basin (LMB) is experiencing an unprecedented boom in river development, with many dams and irrigation schemes being installed. Although general patterns of fish migration are known in the LMB, there is relatively little information on diadromous fish migration, so the overall impacts of river development on their population status is likely underestimated for many species. In this study, we reviewed the available information for over one thousand Mekong fish species to identify evidence for diadromy. Our results found that diadromy is likely a more common life history trait in the LMB than previously assumed. For instance, 61 of the 1136 Mekong fish species assessed exhibit diadromous traits (44 amphidromous species, 9 anadromous species, and 8 catadromous species). Many of these species are known to migrate relatively long distances, connecting with the Mekong estuary to some extent to complete their life cycles. Based on routine fish catch monitoring data, these suspected diadromous fishes contributed around 3% to the total catch across the basin and included a number of endemic species of significant economic value. Riverine development must therefore proceed in a balanced manner to protect diadromous species diversity and associated fisheries resources, whilst also meeting food and energy demands in the region.

Acknowledgements

Special thanks to Fisheries Programme of the Mekong River Commission and the Research Institute for Aquaculture No.2 for the use of datasets for this study. We thank anonymous reviewers for comments to improve the manuscript and Deanna Duffy for making the map. We are grateful to the Australian government, Australia Awards program and to the National Geographic society for providing funding which made this study possible.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Disclosure statement

Authors declare no conflict of interest. An Vi Vu is an Australia Awards scholar but the views and opinions expressed in this paper do not represent the views of the Australian Government.

Additional information

Funding

This study was supported by an Australia awards scholarship to An Vi Vu from the Australian government.

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