Drivers of decline, connectivity and distribution of Brazilian marine fish
Catch-based analysis; seascape genetics; population genetics; distribution modelling; climate change; marine fishery; overfishing
Researchers are worried about fish stock overexploitation, specially marine ones, for decades. To avoid stocks collapse, management measures are needed. However, to do that, some basic information are crucial. In this thesis, the aim is to identify what affects – in relation to environment, climate, biological traits and anthropogenic impacts – the conservation status, connectivity and population structure, and distribution of important species to Brazilian marine fishery. To do that, the thesis is structured in four chapters. In the first chapter, using a catch-based analysis of 60 years of 132 species, we identified a complex interaction that takes species to collapse. Biological, climatic and exploitation factors interact, taking species to collapse: small body size species, exploite by small-scale fishery and negatively affected by warmer temperatues are the ones with higher probability of collapsing. In the second chaptes, we gattered important genetic information for 17 comercially important fish species in Brazil. Using sequence data of COI and CytB, we identified genetic population structure, historical demography and diversity. Except for one, we found no breack on population distributions along the Brazilian coast, indicating that, for most of these species, management measures should consider only one stock occuring in Brazil. We found that most species is in a population expansion process, and that tropical species have higher genetic diversities, what can be related to a higher adaptation capacity to future climate changes. We also found that reef species are the ones with lower genetic diversity, which raises a concern about these already overexploited species. The third chapter objective is identify which seascape characteristics are the most important to explain population connectivity patterns of two marine reef fish species (Lutjanus jocu and Sparisoma axillare). It will also be possible to identify source populations – that are specially important to species maintenance – and sink populations. The aim of the fourth chapter is, through species occurence data gattered with fishers, model the distribution and define priority areas to conservation, considering species use, economical importance and threath.