In recent decades, the wetlands of the Parana Delta have been formed as a territory in dispute between multiple social agents. As part of these tensions, there are proposals that seek to establish a framework oriented towards the conservation of the ecosystem in general and of biodiversity in particular. The objective of this article is to analyze the ways in which the inhabitants of an area of the Lower Delta of the Parana River resignify the prescriptions on the use of what is classified as native fauna and, in particular, of the species that are considered in danger. We argue that the device that conceives the loss of biodiversity as a problem is typical of the phase of the expansion of environmentalism. We propose that the speeches of local inhabitants are shaped by narratives that emphasize the need to conserve native fauna, and we highlight how through ethnographic methodology we have been able to grasp local interpretative frameworks that contrast with the hegemonic technical-scientific discourse that constitute hidden resistance practices. Finally, we emphasize that the locals re-produce the instrumental rationality of conservationist and preservationist logics in certain contexts, while in others they confront them from a substantive rationality anchored in belonging to their place.