A Scientist Walks Into a Bar: The Arapaima

The Field Museum: A Scientist Walks into a Bar event hosted by The Hideout. Photo by L.J. Bailey

The arapaima is a rather robust fish found only in Brazil and Guyana in the Amazon basin. Above is a picture of one of the fish where you can judge its size against a human being’s size. Not too long ago, many of the fish caught were fifteen feet long; today there are no fish longer than ten feet being caught. The arapaima are important to indigenous communities who rely on the fish for food, as well as cultural and religious ceremonies, and when arapaima size and population became alarmingly low, the Amerindians asked the scientific community for help to preserve these animals.

Lesley De Souza had been working on her Ph.D. in Neotropical fish studies when she came across this opportunity to head to the Amazon in Guyana and study the arapaima, and she took it. Part of her plan was to place a radio transmitter on the fish to track their movements. Because the arapaima move into the flooded forests during the rainy season, external transmitters were out of the question as the fish could become tangled in tree roots and injured or even killed. The plan was to surgically implant the transmitters in a cavity in the fish. Lesley studied the specimens in the Field Museum to form an idea as to how this surgery would work and received extensive veterinary advice.

You see, things become complicated because this is a fish that does not breathe underwater. Every five to fifteen minutes, the arapaima must return to the surface where it gulps the air before submerging to rest on the bottom of the water column again. In fact, it is this predictable behavior that led to the conservation concerns today. However, Lesley felt confident that she could perform the surgery quickly so as not to jeopardize the animal’s breathing.

Of course, things in the wild often do not go as planned. When they caught the first arapaima for the procedure, Lesley carefully took her surgical tools to open the cavity for the transmitter. Much to her surprise, the scales were hard, almost like an armor, and impossible to cut through. She started to doubt her ability to perform this procedure, but one of the members of the indigenous community who had provided invaluable information on the arapaima already asked why she wasn’t simply removing the two scales. She hadn’t thought of that and took a hemostat (similar to a pair of tweezers or forceps) to pry the scales free. This became one in a long series of events where the indigenous communities’ expertise proved invaluable, reminding members of the scientific community that it is critical for them to work with the people who know the land best and have been there for thousands of years.

One of Lesley’s biggest surprises was discovering that arapaia secrete milk from glands in their head to feed their young. This was not even well-known in the scientific community until recently, and it was not officially confirmed until an analysis of the stomach contents of a young arapaima showed the presence of signatures of the milk. The indigenous communities were surprised the scientists did not know about the milk – even more proof that scientists need to listen to indigenous people who are experts on their land.

Are there any surprising facts about plants or animals that you have discovered? Tell us about it in the comments. Thank you for reading!

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