‘Taking Fishers’ Knowledge to the Lab’: An Interdisciplinary Approach to Understand Fish Trophic Relationships in the Brazilian Amazon

Abstract

Trophic levels can be applied to describe the ecological role of organisms in food webs and assess changes in ecosystems. Stable isotopes analysis can assist in the understanding of trophic interactions and use of food resources by aquatic organisms. The local ecological knowledge (LEK) of fishers can be an alternative to advance understanding about fish trophic interactions and to construct aquatic food webs, especially in regions lacking research capacity. The objectives of this study are: to calculate the trophic levels of six fish species important to fishing by combining data from stable isotopes analysis and fishers’ LEK in two clear water rivers (Tapajós and Tocantins) in the Brazilian Amazon; to compare the trophic levels of these fish between the two methods (stable isotopes analysis and LEK) and the two rivers; and to develop diagrams representing the trophic webs of the main fish prey and predators based on fisher’s LEK. The fish species studied were Pescada (Plagioscion squamosissimus), Tucunaré (Cichla pinima), Piranha (Serrasalmus rhombeus), Aracu (Leporinus fasciatus), Charuto (Hemiodus unimaculatus), and Jaraqui (Semaprochilodus spp.). A total of 98 interviews and 63 samples for stable isotopes analysis were carried out in both rivers. The average fish trophic levels did not differ between the stable isotopes analysis and the LEK in the Tapajós, nor in the Tocantins Rivers. The overall trophic level of the studied fish species obtained through the LEK did not differ from data obtained through the stable isotopes analysis in both rivers, except for the Aracu in the Tapajós River. The main food items consumed by the fish according to fishers’ LEK did agree with fish diets as described in the biological literature. Fishers provided useful information on fish predators and feeding habits of endangered species, such as river dolphin and river otter. Collaboration with fishers through LEK studies can be a viable approach to produce reliable data on fish trophic ecology to improve fisheries management and species conservation in tropical freshwater environments and other regions with data limitations.

Which fish is this? Fishers know more than 100 fish species in megadiverse tropical rivers

“…However, despite this limited sample size, the interviewed fishers still recognized and named most fish species in the Negro River and all fish species in the Tapajos River, thus even a few experienced fishers could provide useful and detailed information on fish biodiversity. Furthermore, the rich knowledge of fish names by the interviewed fishers observed in this study reinforces the findings of our previous studies in both rivers, which show the fishers' detailed knowledge of several aspects of fish ecology, including diet and trophic interactions Silvano and Begossi 2016;Pereyra et al 2021), migrations (Nunes et al 2019), and long-term changes on abundance (Hallwass et al 2020b).…”

Integrating the local knowledge of fishers into an ecological model for the sustainable management of a protected coastal lagoon area in Uruguay

“…Furthermore , h. malabaricus has been reported as an omnivorous top consumer feeding on insects and fishes (Rosa et al, 2014). Similarly, previous studies showed a consistency of the overall trophic level estimated for several fish species through local knowledge and stable isotopes analysis (Pereyra et al, 2021). In this sense, fishers while manipulate food items may acquire information regarding trophic habits (Ramires et al, 2015).…”

“…This arrangement should prioritize the active involvement of fishers in various aspects of the process, including data registration, stock assessments (specifically biomass data), and the evaluation of results. By incorporating the expertise and perspectives of fishers, the effectiveness of management strategies could be enhanced (Silvano and Begossi, 2012; Pereyra et al, 2021).…”

Improving sustainable practices in tuna purse seine fish aggregating device (FAD) fisheries worldwide through continued collaboration with fishers

“…Even studies by fisheries technologists on industrial purse seine fishing gear are scarce and mostly theoretical (Kim and Park, 2009;Zhou et al, 2019), which warrants more cooperative work with fishers for access to at-sea gear trials. These exchanges of knowledge from fishers to scientists and vice versa are also an excellent way of establishing mutual respect, by highlighting the additive value of connecting both kinds of expertise (Mackinson, 2001;Wedemeyer-Strombel et al, 2019;Pereyra et al, 2021).…”