Effects of sea surface temperature on distributions of two tropical tunas under the shifts of climate periodicity

   Tunas provide an important marine resource for the countries that surround the Pacific Ocean. Under climate change, climate models project an increasing frequency of central Pacific El Niño/Southern Oscillation events but a decreasing frequency of eastern Pacific El Niño/Southern Oscillation events, and may cause sea temperature rising in the central western Pacific relative to the eastern Pacific region and leading to corresponding changes in biological productivity, in turn influencing early life stage of tunas. Consequently, it is crucial to investigate how such climatic periodicity will impact the distribution and abundance of tunas.
   Here, yellowfin and albacore tunas are selected as our study species. Yellowfin tuna prefer warmer environments and have smaller body size and younger age-at-maturation (1 year) compared to albacore tunas (mature in 2 years). We use the spatially-explicit (5° grids) longline catch-and-effort data across 20°N~20°S and105°E~75°W,1970~2015, from Inter American Tropical Tuna Commission (IATTC) and Western & Central Pacific Fisheries Commission (WCPFC). We analyze the spatial and inter-annual variation in the catch-per-unit-effort for the two tunas with respect to changes in sea surface temperature in the central Pacific El Niño/Southern Oscillation events vs. the eastern Pacific El Niño/Southern Oscillation events. To investigate whether the distribution of tunas change under the central Pacific El Niño/Southern Oscillation events and the eastern Pacific El Niño/Southern Oscillation events will greatly help fisheries management and sustainable development of marine resources.