Transport of a sustainably fished pirarucu (Arapaima gigas) from a protected lake under the fishery co-management scheme at the Middle Juruá River, Western Brazilian Amazon. Photo: Marcos Amend
New research has revealed just how valuable local knowledge and communication is when it comes to protecting the world largest freshwater fish in the western Amazon.
The study looked at the local fishers’ work designing protection strategies for the pirarucu, and how this can be applied to other socioecological systems within and beyond Amazonia using spatial networks metapopulation modelling.
The international collaboration of researchers includes Dr Miguel Lurgi, from the School of Biosciences, Geography and Physics, and their findings have just been published in the Journal of Applied Ecology.
In the Middle Juruá River Basin in Western Brazilian Amazon, the locals’ protection of oxbow lakes is helping save the pirarucu (Arapaima gigas) from the brink of extinction, benefiting biodiversity and the wellbeing of the local community.
The choice of which lakes to protect is made by experienced local fishers, relying on both generational trial-and-error ecological knowledge of river seasonal dynamics and fish behaviour.
This local knowledge is combined with regulatory policies defining annual fishing quotas for lakes within a co-management scheme and aims to guarantee not only sustainability but also prevent illegal fishing.
Even though local choices and governmental regulations have proven to be successful, the researchers sought to help the community discover if their judgment really is the best option and assist managers and governments to expand this initiative across the Amazon.
Given that large-scale empirical experiments are challenging, especially in remote areas such as the heart of the Amazon, the team developed six alternative scenarios for the fishing co-management, based on pirarucu population data collected from 2011 to 2022 by local fishers across 13 community-based protected and 19 unprotected lakes.
They built up a spatial network in which the 31 studied lakes are connected or not depending on their geographical position, status of protection, and pirarucu ecology. This baseline was then used to develop a population model that accounts for the number of pirarucu adults in each lake over time, how much the population can grow and how many fish each lake supports (its carrying capacity). The alternative scenarios proposed involved changing which lakes are protected based on how lakes connect to each other, their area, geographical position, carrying capacity or simply without any criteria.
The authors also modelled different levels of illegal fishing in the unprotected lakes, and the results were striking.
While a model-driven strategy based on the lakes’ carrying capacity may provide the most efficient outcomes, the researchers revealed that the existing co-management scheme performed nearly as well. This highlights the importance and reliability of fishers’ local knowledge because community-managed lakes maintained high pirarucu populations and provided critical refuges that buffer against overexploitation elsewhere.
Computational ecologist Dr Lurgi said: “Our study represents a pioneering step towards a better integration of traditional knowledge of local people into quantitative ecological approaches to the sustainable management of natural resources.
“By fully integrating social and ecological aspects of population management into quantitative predictive frameworks, we will have a better chance of providing policymakers and local communities with the tools needed to better address challenges at the interface between conservation and sustainable development."
Beyond the insights to the Middle Jurua region and the Amazon, the team say their work provides a roadmap to integrate local knowledge and ecological modelling to advance sustainability in complex ecosystems worldwide.
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