The smallest smallest – because migration is not just a matter of size

The smallest smallest – because migration is not just a matter of size
May 25, 2020 AmazCitSci

By Vanessa Eyng y Guido Miranda

Collaborators: Claudia Acosta and Gina Leite

 

The Tacana people are located in the Bolivian Amazon. Many of its members live in the Tacana Community Land of Origin, on the plains of the Beni River. When the tacana want to accentuate something in their language, they repeat the word. Let’s see an example.

The word chipi, in tacana, means small. If something is very small, the chipi becomes chipi chipi. The repetition  leaves no doubt: we are talking about the smallest.

This is how the tacana name the fish whose scientific name is Trichomycterus barbouri. This fish measures about 3 centimeters and weighs only 0.38 g when juvenile. Nothing fairer than to double the word in the case of those catfish.

Chipi chipi, like many other fish, migrate in annual cycles. Local knowledge and recent observations made through participatory research will record that the Chipi Chipi migrate about 400 kilometers upstream from the floodplains of the Beni River. These data were shared in the article First observations on the annual massive upward migration of juvenile catfish Trichomycterus in an Amazonian river.

Chipi chipi make their juvenile migration in an average of 32 days, usually between February and March. They swim against the current about 12 kilometers a day. All this to reach the Andes mountains to spawn. Closing the cycle, when they become adults and reproduce, their eggs will go down the same path, carried by the current of the river, completing a migration cycle of almost 800 kilometers. An impressive feat and a tremendous effort for such a small fish! We show you that in the video El viaje del chipi chipi:

 

Memories of a joint work

“From the first time I saw some schools of chipi chipis in 2011, on a trip to San Miguel de Bala, I couldn’t believe what I saw, it was something totally unexpected, Trichomycterus migrating! From that moment on we coordinated with several Tacana fishermen and friends from Rurrenabaque an observation network of the chipi chipis. The purpose of this network: to alert with the time necessary to go from La Paz to Rurrenabaque and to be able to document this phenomenon. Since they only pass through Rurre for a few days, and not all the schools are visible, it was crucial to be able to go at the exact moment. The following years reported to us that they saw small schools arriving, but it could not be guaranteed that they will continue to be seen until we arrive. We wait until 2014 to have the right moment. Each and every one of the members of this network called us saying that there were large schools and that they were already climbing. We flew with my colleague Gustavo Álvarez, as soon as possible, and when we arrived, we went directly to the boat to see the schools. There was just one passing through Rurrenabaque, the images of the fishing were taken at that very moment. We documented the fishing and then we went to the area of the straits where we saw them glued to the rocks and passing in a row, it was incredible. The villagers, used to seeing and using this migration, laughed at our expressions of astonishment. It was one of the most rewarding and revealing experiences in my career, having before me a phenomenon that would change our way of seeing this group of fish and the Amazon in general, for all that remains to fall in love even more with her beauty” – Guido Miranda Chumacero, from WCS Bolivia and associate researcher at the UMSA Institute of Ecology.

 

The importance of migration for fish

Migration is a vital strategy for fish. Opportunistically, fish move in search of food, to find suitable places for their reproduction, as well as respond to changes in the environment. In environments such as the Amazon Basin, these changes are extreme and define the biological cycles of most species of fish.

Migration movements are also fundamental in the management of fisheries. More than being lucky, knowing where and when fish are migrating is fundamental knowledge for those who fish. In his work, observing the environment and knowing the behavior of the fish defines much of the success in fishing, which is a fundamental source of food and income for thousands of people living in the Amazon Basin. 

Interruptions in the connectivity of rivers, poorly planned works, overfishing, climatic changes and alluvial mining have great impacts for the fish and for the people of the Amazon. In the case of Bolivia, in areas where the chipi chipis migrate, there is increasing pressure to exploit gold.

In the Beni and Kaka rivers, near the Madidi National Park and the Tacana Community Land, for example, now large dredges are found sucking stones, earth and sand from the bottom of the river, which alter the hydrogeomorphology of the river and pollute with mercury the area and downstream. In addition to the dredgers, it is also possible to find the ‘carancheros’, searching for gold with their small rafts. The impacts of these activities, often illegal, can bring irreversible changes in the fluvial dynamics of rivers. This translates into species losses as well as risks to food security, health, and the livelihoods of the peoples who live in these areas and who depend on biodiversity on the move.

The path that the chipi chipi take along the Beni River and its tributaries. Map: Guido Miranda Chumacero.

 

Where do the chipi chipi go

The migration of the chipi chipi occurs in the Beni River, which is one of the largest tributaries of the Madeira River basin, which in turn is one of the most important in the Amazon Basin. The Beni River, by itself, is one of the largest rivers in Bolivia, 1010 km long. Its flow discharge, which is nothing more than the volume of water that passes through a section of the canal per unit of time, is 2050 m3/s near the Bala Strait. Sediment discharge, which is a measure to understand the amount of sediment that water brings, is estimated at about 190 million tons per year in the Rurrenabaque region.

The Beni River is born as the Tallija River in the Central Cordillera of the Bolivian Andes, becoming the Beni River at the confluence of the Alto Beni and Kaka rivers. From there it also receives the waters of the Hondo, Quiquibey and Tuichi rivers, before passing the straights of the Bala and Suse cliffs as the last Andean foothills and then opening onto the Amazon floodplain. In the floodplain, the Beni forms innumerable meanders that gradually form characteristic lakes of the Amazonian rivers.

 

Swimming Upstream

The migration of the Chipi Chipi is related to three main areas: floodplains; the straits; and the mountainous areas. At each point, the behavior of the fish is given according to the flow they face. In the floodplain area, the schools remain close to the riverbanks and also close to the surface.

At that time they are in the Rurrenabaque region, where the fishermen are waiting for them to start their fishing. These small fish are highly valued in the region and represent an important, albeit seasonal, source of protein and energy (due to the fat they accumulate) for people. In families it is common to collect up to 50 kilos of chipi chipi during migration, which represents about 166 thousand individuals. Many are eaten as dunucuavi, a typical way to roast fish in patujú leaves.

After Rurrenabaque, a significant challenge for the chipi chipi is to beat the rapids. At the points where the current is strongest, such as the Suse and Bala Straits, they use the stones to overcome the force of the water. At this point the shoals move along the rocks on the banks, climbing and holding on to them with their tiny teeth, passing as if ordered in a queue!

The chipi chipi reach the last mountain ranges of the Andes, 400 meters above sea level. In that area, where the river is shallower and with less volume, the schools are more dispersed at the bottom of the river. There they will reproduce as adults and their eggs will now be the ones that begin their journey, going down the river with the help of the current.

Throughout this journey, a long one for such a small fish, the migration of the chipi chipi is closely related to the cycles of the river and changes in the environment. Migrations represent the beginning of a series of temporary changes in the composition of the river’s fish communities and, therefore, if in relatively dry years the relative size of the migration is reduced, this change may have unknown consequences for the rest of the aquatic community and the ecosystem.

The citizen science approach in the Amazon is fundamental to create a space for dialogue between different ways of generating knowledge – with this we can, for example, learn more about migration patterns. This helps promote the sustainability of activities so important to people, such as fishing, and empower fishermen for the sustainable management of fisheries and the conservation of Amazonian wetlands.