Dinâmica populacional de duas espécies de peixe-agulha, Hyporhamphus unifasciatus e Hemiramphus brasiliensis: uma abordagem etnoecológica

Abstract

Declining fish populations, as a consequence of anthropic environmental changes, such as climate change, and overfishing, can affect the economic income of artisanal fishermen. Due to climate change, organisms are forced to migrate or adapt to new climates and, if they do not, they risk to decline and become extinct. It is known that local fishing populations, by using and knowing the resources of the environment, accumulate knowledge about changes and environmental processes and can perceive the decrease in the abundance of resources and assist in the detection of possible changes in the availability of species. In this context, this thesis aimed to investigate two complementary aspects regarding two species of halfbeak, Hyporhamphus unifasciatus (ballyhoo halfbeak) and Hemiramphus brasiliensis (common halfbeak), two small pelagics of relative fishing interest and of high relevance in the trophic chain. The first of these aspects investigated how the environmental changes caused by anthropic actions in coastal waters will affect the distribution and supply of halfbeak species in the Americas over the next 30 and 70 years? The second aspect investigated whether it is possible to make a historical rescue of the supply of these resources from the perception of local fishermen. Using Bayesian Species Distribution Models (B-SDMs), we identified that both species are more likely to be found in shallow, warm and salty waters. The model's prediction suggests that both species are likely to benefit from climate change, with a potential increase in their area of occurrence in the coastal regions of the Americas, especially due to the increase in temperature and the increase in salinity, provided they find favorable habitat for this. For the second question, we conducted 18 semi-structured interviews with specialist fishermen selected with the snowball technique in three locations on the coast to obtain information about possible changes in the abundance of populations over the years. We also compiled data on the reconstruction of the catches of the two species from 1950 to 2010. To check whether the variation curve in the official catch corresponded to the variation curve, according to the perception of experts in this fishery, we selected the years cited by them as being the best. In the perception of fishermen, variation in the availability of species and reduction in the quantity caught was identified, although the analyzes indicated that there was no difference in the perception of availability and that there was no change in the available quantity of this species in their fishing zones.