Overexploitation and behavioral changes of the largest South Atlantic parrotfish (Scarus trispinosus): Evidence from fishers' knowledge

Assessing species conservation status and population trends is challenging especially on low and low-middle income countries mostly due to high costs. Therefore, long-term information about species gained through local ecological knowledge, can reveal threatening and overexploitation scenarios aiming to generate information for extinction risk reduction and conservation priority targets. The greenbeak parrotfish, Scarus trispinosus, is an endemic and endangered Brazilian species with records of local extinction along its distribution, however limited data on its fisheries is available. We investigated fisher's local ecological knowledge on S. trispinosus on the largest Brazilian coastal multiple-use marine protected area. We interviewed small-scale fishers regarding catches to verify temporal changes in abundance and body size. Additionally, we verified if S. trispinosus flight initiation distance, proxy of tolerance from fisher's approximation has changed over different fishers' generations. Our results revealed that the number of individuals decreased 64% over time from 1980s to 2010s with a constant decrease through time. The weight of the largest individual ever caught also decreased 67% over time. Flight initiation distance, when fishers firstly engaged on fishing activity, was smaller for more experienced fishers. Implementation of small-scale co-management strategies, together with creation and enforcement of no take zones are essential to safeguard the remaining populations and allow the greenbeak parrotfish recovery. Our study demonstrated that local ecological knowledge on species population and behavioral changes can be used as an alternative and inexpensive approach for assessing impact on threatened species and could be applied on conservation strategies for several species and ecosystems worldwide.

Automated summary

Assessing conservation status and population trends of species, particularly in low and low-middle income countries, is challenging due to high costs. Utilizing local ecological knowledge can provide important information for extinction risk reduction and conservation priorities. The study on greenbeak parrotfish in Brazil revealed a significant decrease in population numbers and individual size over several decades, highlighting the importance of small-scale co-management strategies for conservation.