Limnology in Thailand: Netting Samples (and Dinner) on the Chao Phraya River

While a lot of what we do at the Center for Limnology is all about Wisconsin waters, we’ve got some world-class research going on all over the world, from places like Tanzania and Thailland. Aaron Koning, a grad student in Pete McIntyre’s lab, is working on understanding the fish communities in both the Chao Phraya and the Mekong rivers in Thailand. Both of these major rivers support important, but threatened, fisheries.
Aaron recently wrote in with this dispatch from the banks of the Yom River, a tributary of the Chao Phraya:

Following Pete [McIntyre]’s return to the U.S., I set off to repeat the fish community collection and nutrient limitation experiments that we had conducted previously in the Salween River basin. While I had intended on conducting this second round of work on a Mekong River tributary, the site at which I had access turned out to be less than ideal.
Already set back a week due to illness, I decided to return to a community that I knew well in central Thailand on a tributary of the Chao Phraya river, rather than seeking out a new site and trying to rush introductions to a new community of people.

The Chao Phraya, which drains most of northern and central Thailand, along with the Mekong River are thought to have once formed a “super-river” long ago when decreased sea levels exposed much of the shallow continental shelf below the Gulf of Thailand. As a result, the fish species of these two large river systems are largely overlapping.
Once in the area, I spent two days driving around northern Thailand setting up in-stream experiments to test whether nitrogen, phosphorous, or both may be limiting primary production (plant or algal growth) in any of five major rivers in the region. Once those were deployed in each location, I settled into  a riverside village on the Yom River. With the help of two fishermen setting nets and dip-netting in riffle areas, I was able to complete a second food-web collection during my fifteen days in the village. L
iving and working in a rural Thai village means that “Action Packer” storage bins become lab benches, and I sample fish muscle tissue while the family watches Thai soap operas. It also means any fish not retained for my collection end up as dinner.

The local fishermen were a great help, and I was able to collect close to 50 species of fish during my time there. While I am sure I failed to collect a number of species, the locals assured me that there were only a few more rare species that we had not encountered. The fishermen did, however, manage to catch a freshwater sole (Brachirus harmandi) and freshwater pufferfish (Monotrete cochinchinensis) as well as many species of cyprinid minnows, loaches, catfish, three species of snakeheads, and one freshwater goby. Whenever possible, individual specimens were retained, preserved, and then brought back for inclusion in the University’s Zoological Museum.
Once I got export permits for fish specimens and water samples, I returned to the U.S.

Now back in Madison there is still plenty to do. There are tissue samples to grind and weigh before I can analyze for stable isotopes to get a better understanding of the food web and nutrient cycling. I also have water samples to analyze in the Water Science and Engineering Lab; and field identifications must be verified on fish specimens. The results of these exploratory collections and experiments will help shape my research goals for my extended stay in Thailand. Nine months form now, I’ll return and settle in for a full year of doing science along the Mekong and Chao Phraya rivers.