For the past two years I have been studying Arapaima movements in the Rewa River drainage and tracking 29 individual Arapaima with Shedd Aquarium. A pattern has emerged highlighting that the majority of these tagged individuals are returning to the same place where they were originally tagged. If these Arapaima are returning to the same location in the dry season, where are they going when the rainy season floods the forests as far as you can see? We have attempted to track them as the water level begins to rise, but then in a flash they are gone and far into the flooded forests. So where are they?
Getting Off the Ground
Arapaima are endemic to tropical South America, primarily found in the Amazon and Essequibo River drainages. These ancient fish are often times referred to as the “dinosaur” fish and can reach lengths of nearly 10 feet and weight more than 400 pounds. They have persisted through millions of years of dynamic geological history and climatic changes of South America, but recent fishing pressures on Arapaima have made them a vulnerable species throughout their range. Tracking their movements is critical and will enable us to determine what extent of the river drainage they utilize, and determine critical feeding and breeding habitat. Movement data will also help to inform management plans for this species as protecting Arapaima has broader impacts, as a flagship species, and will thus preserve habitat with high biodiversity.
Conventional methods to locate Arapaima using a boat can be costly, time consuming, and practically ineffective during the rainy season. Looking for a better way to track our fish, we had to consider alternative options. No one has ever used aerial tracking to locate Arapaima, so we decided to test its feasibility at the end of the dry season in the Rewa River when most of the tagged Arapaima are in ponds or oxbows disconnected from the river. Before going up in the air, I tracked all tagged fish to confirm their locations by boat, then set out to Ogle airport in Georgetown, Guyana. Aerial tracking has never been done in Guyana so this was new and fascinating to the plane company, Air Services, as well. Once all the proper permissions were in place and I had a pilot eager to embark on this adventure, we took off from Georgetown.
Taking to the Air
It’s difficult to paint the beautiful picture I saw from the plane. The expansive lush rainforests of central Guyana lies below as I peer out the window of the small bush plane. The meandering rivers of the Rupununi region that eventually flow into the Amazon basin glisten in the sun. The sheer scale of the Rewa River drainage from an aerial perspective gives credence to the daunting task in searching for anything in the rivers or forests below, much less a radio-tagged Arapaima that may have swum into a new creek, oxbow or site on the river.
As we approach Rewa, we take out the airplane doors and my heart begins racing as I interact with the outside air and see the forest and river below. The anticipation is palpable as I approach one of the first ponds. With headphones on, I listen for the radio-tagged fish as the pilot circles the pond beneath us where I tracked them previously from the boat. And then there they are! I hear a signal! We proceed to the next ponds to confirm if previously observed Arapaima can be found, and again we hear the signal – loud and clear. The clarity is unbelievable, allowing me to specifically pinpoint the location of each individual from the air. Taking time to search for individuals that were missing from their last relocation, I’m able to find them in new locations – ones that I’d never been to. Only the engine and wind were able to hear my excited cheer as I realized the incredible potential of aerial tracking. Finding missing Arapaima using aerial tracking during the dry season, makes me hopeful that the technique will be effective during the rainy season.
Onward and Upward
Aerial tracking was successful over open ponds and creeks with forest cover, therefore our plan is to utilize this method in the rainy season when I return to Rewa in the peak of the rainy season (July/August) to locate the tagged Arapaima. Our goal is to determine maximum distance of radio-tagged Arapaima during the rainy season to elucidate their yearly migration patterns. Rewa Villagers’ decision to no longer harvest Arapaima has resulted in a rebound in population numbers and if Arapaima movements are within their river basin, then populations will continue to grow because they will be protected. Having data on the maximum distance Arapaima are moving will have a direct impact on Rewa Villagers’ efforts to make Rewa River drainage a conservation area recognized by the Guyanese government.
Dr. Lesley de Souza holds a two-year postdoctoral research position that continues Shedd’s research in Guyana’s North Rupununi region, where intensive fieldwork is needed to assess and protect the area’s rich aquatic biodiversity. Dr. de Souza’s work will help conservation managers understand the role that Rupununi wetlands play in supporting fish diversity, which in turn will help establish scientifically sound fishing regulations. She also plans to identify and monitor the migratory routes and nesting sites of arapaima, one of the largest freshwater fishes in the world. Additionally, Dr. de Souza will study the physiological impacts on Arapaima that are captured by sport fishermen.