The Mekong giant catfish, though not cuddly, is adorable enough to save

TIME article

This month's issue of TIME reported on just a few of the most endangered species of the world. Most were not surprising. However, the Mekong giant catfish is startling at the least. If the shock of its size is not enough, imagine it's context - imagine an American soldier in the 1960s on the Mekong seeing a giant catfish for the first time.

Pangasianodon gigas is one of the largest freshwater fish, and it is migratory. Migrating fish face fierce foes: proponents of dams. For a great example of how we can create danger for fish right here at home in the US, see "salmon" and "Pacific Northwest." Some tributaries of the Mekong River, including the Mun River of Thailand (for discussion of dams and migratory patterns of giant catfish, see Hogan et al., 2004 "The Imperiled Giants of the Mekong").

Impaired migration might be one reason for their "critical" endangered status. But what else? The fish is legally protected from hunting, yet this might still contribute a portion of its decline. Something interesting to consider might be - did the Vietnam War have some environmental impact on them? Is their plight isolated, or are other aquatic and terrestrial organisms similarly diminished in the area? Is the effect on the giant catfish due to its place as a predator of many fish, fish that may be contaminated with legacy chemicals?

While I'm sure someone has potentially connected these dots, I haven't been able to find a direct statement. Of the herbicides used during the Vietnam War for defoliage and destruction of crops, Agent Orange comprised 61% of the 72 million liters used. Agent Orange is a 50/50 mixture of 2,4-D and 2,4,5-T; both toxicants in their own right (as well as endocrine disruptors!), the mixture was often contaminated with dioxin, a known carcinogen and thyroid disruptor among other effects. A report from 2001 (and others from the early 2000's) suggest that dioxin levels in the soil, water, wildlife, and human sera/breast milk of residents of Vietnam contain dioxin levels similar to the 1980's - i.e. they are relatively stable. So dioxin is a persistent nightmare for Vietnam, especially areas close to historic military storage areas, and the dioxin present from military installations may still be leaching into the environment (see PMID 11993628, Dwernychuk et al. 2001).

Though elevated dioxin in fish can be confirmed, it doesn't connect back to whether or not this contributes to the collapse of the Mekong giant catfish. Monitoring and tracking of the fish is a last ditch effort to save it - maybe when they tag those fish, they could get a blood sample for a dioxin test?