The Giants that live within the Nine Dragons
By Taylor Chenette
The nine dragons of southern Vietnam breathe in and out twice a day during the dry season. During the monsoon season, the dragons only breath in and out once a day. The breaths are the tidal exchange of fresh and salt water, from river to sea. The dragons represent the major tributaries of the Mekong Delta; in Vietnamese: Đồng bằng Sông Cửu Long, or River of Nine Dragons. Within those dragon breaths, giant aquatic species migrate in and out.
In scientific terms, a species must be capable of growing to at least two metres [6.6 ft.] in length or 100kg [220.5 lbs.] in weight to qualify as a giant fish.
–World Wildlife Fund.
Four of world’s most giant fresh water fish are found in the Mekong River. The first is the Giant Freshwater Stingray (Himantura chaophraya) which can weigh up to 1322.77 lbs. (600 kg), then the Mekong Giant Catfish (Pangasianodon gigas) with a max recorded weight of 771.6 lbs. (350 kg) followed by the Dog-eating catfish (Pangsius sanitwongsei) and the Giant Barb (Catlocarpio siamensis), both with a max weight of 661.4 lbs. (300 kg).
The existence of these giants is ecologically and culturally significant. They are vulnerable to changes in river conditions and flow, and several are endemic to the Mekong. Around 87% of the Mekong’s known aquatic species, including the giants, are migratory. They rely on different segments of the river for variation in habitat and brackish or freshwater, based on their life-stage. The river, and its diverse migratory species, are threatened by hydropower dam infrastructure. Dams obstruct sediment transportation, water flow rates, and tributary connectivity – all key characteristics of the Mekong’s habitat. There are currently 12 proposed dam projects for the lower Mekong.
The 1990’s saw a major shift from fishing to aquaculture due to several factors including, but not limited to, over harvesting of wild fish populations, an increase in human populations and demands for fish supply, and new developments in aquaculture technology. A species of pangasius, or catfish, is common choice for aquaculture. Vietnam provides over 90% of the world’s catfish exports. Escaped farmed fish, developed from cultures, pose a threat to wild fish via cross-breeding, disease spread, and competition for habitat. Scientists at Can Tho University are researching and developing immunizations to decrease disease risks.
Fish disease researcher checks on the status of her catfish barrels.
The Mekong is second to the Amazon river in biodiversity. Over 1,200 freshwater species inhabit its waters, with over 45 new species of fish discovered between 1992 and 2004. The river produces around 2.6 million tons of fish per year, making it the most productive inland fishery in the world. Conservation and protection of this mighty river is important, especially as there is plenty to still be discovered and understood about the Mekong and its nine dragons.