Monitoring Cantão Fish Population and Dispersal

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The project Monitoring the Ichthyofauna of Cantão State Park, started in August 2013, aims to monitor the recovery of fish populations in lakes with effective protection, and also demonstrate the effect of these lakes in the fish repopulation of areas around the park , where fishing is allowed.  Important fish for commercial and sport fishing will be marked and recaptured in the protected lakes, and, with the participation of local fishermen, their estimated population and their dispersal to areas where fishing is allowed will be accompanied.  At the same time, there will be an annual census of pirarucu fish (Arapaima gigas), allowing a comparative analysis of their presence between unprotected lakes and those with permanent surveillance.  So, with the support of the Brazilian Fundação Grupo O Boticário, the Instituto Araguaia (IA) will be able to demonstrate the importance of protecting the lakes in Cantão for the recovery of fish stocks in the medium Araguaia.


Cantão State Park contains more than 850 lakes - 80 % of all lakes in the Araguaia basin. This abundance of lakes, combined with the high productivity of its igapós, makes Cantão one of the best freshwater fish habitats on the planet , with 301 species cataloged to date - more than in all of Europe, and more than in the entire Pantanal basin.

Currently, the major threat to the ecosystem of Cantão is illegal poaching. With the growth of the State of Tocantins in the last decade, both professional fishing and sport fishing have grown dramatically. The price of fish in the region has increased over 1000% since 2001, and stocks of the most sought after species are collapsing throughout the Araguaia. Consequently, the lakes in Cantão are under increasing pressure from fishermen who invade the park, constantly taking away significant amounts of fish.  In addition, when camping inside the park, these invaders can cause fires that devastate large areas during the dry season.   A single raid by fishermen can destroy the brood stocks of several lakes, thus requiring constant surveillance in order to protect these nursery grounds.

In partnership with the park agency Naturatins , Instituto Araguaia carries out the necessary surveillance in a set of 20 lakes around its research base. IA officials take turns patrolling the area 365 days a year. Researchers, assistants and volunteers constantly roam the park’s trails, and, if necessary, call for support from Naturatins.  As a result of this constant presence, invasions and illegal fishing were reduced to negligible levels in lakes around the base, and the fish population in these lakes has increased markedly in recent years.  The amount and size of large pirarucus residing inside the protected lakes is remarkable, and informal interviews with local fishermen indicate that fishing in the neighboring Rio do Coco, where fishing is allowed, has improved in recent years.  This project intends to demonstrate this.

Methods and Objectives:

The project consists of two components:

1 - Monitoring and comparing the presence of pirarucus in three lakes with different levels of effective protection.

This monitoring program uses the counting method developed by researchers at the Institute Mamirauá, in the Brazilian Estado do Amazonas.  Counts will be made in three lakes: (i) Lago das Ariranhas, next to the IA research base, which has not been fished for over ten years; (ii)Lago da Praia, near the base, which has not been fished for two years, and (iii) Lago do Cega-Machado, who has suffered the invasion of net fishing poachers in 2012, but was the site chosen for the implementation of the Ecotourism Project (ProCantão) as well as the Giant Otter Project.  The permanent use of these trails by AI researchers and by the ecotourists should result in a drastic reduction in illegal fishing hereafter.

2 - Mark- and -Recapture of important fish to the regional fisheries .

Commercial and sports fish will be captured in the protected area near the IA research base.  Focus will be given on the characiform species such as piraña, pacu, piau and curimatã fish. Besides their importance for the regional commercial fisheries and for local people’s sport fishing and subsistence, these fish are the basis of the food chain of the Araguaia, providing food for larger fish and other predators.  The fish will be marked with numbered plastic tags, and the species name, location, weight, and date of capture will be recorded.  Fish of various sizes and types will be marked during every month of the year for the next 2 years, in order to establish their lifecycle and to define their dispersion according to the periods of floods and droughts. The goal is to mark 3,000 fish during the 24 months of the project.  Fish tagged and recaptured in the same lake by the project's team will have their population estimated, and changes in species composition from one year to another will also be recorded. The project will be widely publicized in the local fishing associations, to ecotourism guides and boatmen and other forums, with a reward of R$10 (ten Brazilian reais) per brand returned with information about the location and date of capture, encouraging the community to participate in the project and generating data on species dispersal.

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