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

A key step in facing a crisis is to identify the most vulnerable targets. The current biodiversity crisis is threatening all the world's ecosystems, causing the sixth mass extinction on Earth. The marine ecosystem is no different, over 60% of fish stocks are already threatened due to overfishing, climate change, pollution and habitat destruction. In the terrestrial environment, it seems clear that larger organisms are the most threatened because they are easier and more valuable targets and because of characteristics of their life history, such as the fact that they usually have slower growth and produce less offspring, among others. When considering fish, understanding their most vulnerable traits is not so obvious. Smaller species at low trophic levels are also fishing targets and are apparently more sensitive to climate variability. Larger carnivores are more valuable targets, and their response to environmental changes is slower, which may be an advantage after all. Using a catch-based analysis, we identified the exploitation status of 132 commercially valuable fish species in Brazil using four categories: Collapsed stock (when current catch is less than 10% of historical maximum catch), Overexploited, Fully Exploited and Development.

 

Figure 1: Graphical abstract of the study.

 

Based on this exploitation status, we identified which combination of characteristics and external factors (climate and fisheries) makes species more vulnerable to stock collapse. The biological characteristics tested were maximum body size, trophic level, preferable habitat (reef, demersal or pelagic) and resilience. As external factors, we tested sea surface temperature, sea surface salinity, type of fishing (industrial versus small scale) and price. We found that the two most important factors affecting vulnerability to species collapse were the response of species to sea temperature and species size. Smaller species negatively affected by higher temperatures are the most threatened. We suggest that overexploitation of species with vulnerable biological characteristics affects the way species respond to climate variability, making them more sensitive to warmer temperaturas.

 

Check out the entire paper here:

 

Verba, J. T., Pennino, M. G., Coll, M., & Lopes, P. F. (2019). Assessing drivers of tropical and subtropical marine fish collapses of Brazilian Exclusive Economic Zone. Science of The Total Environment, 134940.

 

By Julia Tovar Verba