Last week postdoctoral research associate Dr. Lesley de Souza returned to Shedd from her third field season in Guyana studying arapaimas, South America’s largest freshwater fish. She shares her latest experiences here.

I’m back in Chicago from three months in the North Rupununi region of Guyana! It was a great field season. Here’s a short update and a few photos.

I was able to relocate 15 of the 18 arapaimas we tagged with radio transmitters in 2013. Most of these individuals returned to the same ponds that I located them in a year ago. Also, many of them were in the exact same spot using the same nest, which is pretty remarkable. (The nests are remarkable too — depressions in the bottom of the river so large that I can fit inside some of them!)   During the rainy season last year I only found five of these fish because they had moved far into the flooded forest.

We inserted transmitters about the size of AA batteries into 10 more individuals, for a total of 28 arapaimas with radios. Another focus of this trip was to examine arapaimas that were tagged one year ago and one month ago to measure growth and monitor how they were healing. This proved challenging as the fish evaded the net pretty well. We successfully collected two arapaimas that were tagged in January 2013 and two tagged in March this year. The 2013 individuals had no sign of surgery. The scales had completely regrown. The 2014 fish had already begun to regrow scales, and the incisions had completely healed. We also found surprises in the net: caimans, giant river turtles, electric eels and a large stingray.

The most epic moment of the trip was collecting an 8-foot arapaima — easily 400 pounds! Individuals this size are increasingly rare to see in the wild throughout the species’ range. None of the villagers with me had ever seen one that big, and an elder in our group said he had not seen one that size since he was young. Most exciting is that this particular pond has several large arapaimas, which is promising for the conservation of this species.

Twelve fly-anglers were in the village of Rewa to fish for arapaimas while I was there. Through the new catch-and-release arapaima sportfishing program, anglers have become involved in the research by pit tagging, measuring and collecting other data on arapaimas they land with the Rewa fishing guides.

I traveled to Georgetown, Guyana’s capital, to meet with President Donald Ramotar to discuss the progress of the research. I am hoping he will join us in the field next season. I also participated in a two-day meeting to discuss revising the arapaima management plan to incorporate the sportfishing program and the findings of my research. Attending this meeting were the North Rupununi District Development Board (the governing body over 16 Amerindian villages) and representatives of the Ministry of Agriculture, Environmental Protection Agency and Ministry of Amerindian Affairs.

Our crew for this field season included others from nearby villages and a biology student from the University of Guyana. Awareness of our research project has now expanded as far as the South Rupununi, where arapaimas are no longer present due to overfishing.

Enjoy the pics!

Lesley de Souza, Ph.D.