Assessing drivers of tropical and subtropical marine fish collapses of Brazilian Exclusive Economic Zone

Abstract

Overfishing is a concerning threat that can lead to the collapse of fish stocks. We assessed the combinations of factors, including biological traits, types of exploitation and responses to sea temperature and salinity changes, that drive species to collapse in the Brazilian Exclusive Economic Zone (EEZ) tropical and subtropical regions. We applied a catch-based method of stock classification and a catch time series of 61 years from 132 exploited fish species. Species were categorized as Collapsed, Overexploited, Fully Exploited or in Development, and we used a GAM analysis to understand their categorization over time. Furthermore, a Redundancy Analysis was developed to assess the species characteristics that best predicted each exploitation category. Twelve species were classified as Collapsed, 55 as Overexploited, 46 as Fully Exploited and 19 as in Development. Tropical and subtropical exploited species collapses in Brazil were best explained by a complex combination of a negative impact of warmer sea temperatures, fishery exploitation and specific life-history traits. A synergistic interaction between these factors could bring species to collapse. We hypothesize that the exploitation of species with vulnerable traits may alter how these species respond to temperature and, therefore, lead them to collapse given that intense exploitation may affect their ability to respond to temperature increases. Measures to mitigate climate change impacts should take into consideration incentives to decrease the exploitation of vulnerable species and, specifically, consider species with more sensitive biological traits. Such measures are also important to minimize the socioeconomic impacts on the people that depend on these species.