Counter intuitive effects of an extreme Indian Ocean Dipole event on a coupled human and natural system in Southern Myanmar.

Krista A. McCoy, Iris W Segura-García, Steve J Box, Michael W McCoy

The Indian Ocean Dipole (IOD) is a major climate cycle that occurs across the tropical Indian Ocean which has become more variable over time substantially influencing weather extremes and broader climate patterns worldwide. Importantly, these large scale global and regional scale climatic events have strong unexpected impacts on coupled human and natural systems at local scales. One of the strongest negative IOD events ever recorded occurred in 2016 and induced downwelling, decreased chlorophyl-a, and reductions in small pelagic fisheries in Java and Sumatra regions of Indonesia. Here, we use a digital daily catch data collection system to characterize the diversity and volume of fish catches coming from the small-scale fisheries of the Myeik archipelago in Myanmar before, during, and after this 2016 IOD. Unlike Java and Sumatra, total catch (Kg) of pelagic, reef, and demersal fishes increased through 2016 as the negative IOD intensified. Demersal fish accounted for a larger increase in catch than pelagic or reef fish in 2016, but total catches from all three habitats began to decrease in January 2017 as the dipole weakened, with many taxa becoming uncommon or absent by the end of 2017. These data are counter intuitive as negative dipole events are typically associated with reduced productivity in the eastern Indian Ocean. However, the Bay of Bengal and Andaman Sea was buffered from the strongest temperature increases. The increase in landings in Myanmar might have stemmed from northern migration of species to cooler more productive waters in the less impacted Andaman Sea. As climate change intensifies, we need to determine how fish populations respond to variable climatic events. The IOD cycle might function as a recurring phenomenon with locally predictable effects that can inform an ecosystem-based approach to fisheries management to help ensure the long-term sustainability of this coupled human and natural system.