Effects of seamount characteristics in Central and Western Pacific Ocean on CPUEs of yellowfin tuna (Thunnus albacares) in longline and purse seine fisheries

Seamounts are one of the important habitat types on the seafloor and a hotspot for marine biodiversity. Yellowfin tuna (Thunnus albacares) is widely distributed in the Western and Central Pacific Ocean (WCPO) with high ecological and economic value. However, there are few studies on the mechanisms by which seamounts and their associated features affect the abundance and distribution of yellowfin tuna resources. In this study, we used longline and purse seine fishery data summarized by the Western and Central Pacific Fisheries Commission (WCPFC) from 2010–2021, in addition with seamount characteristics data, to analyze the impacts of two different types of seamounts on the abundance and distribution of yellowfin tuna resources using a generalized additive model (GAM). GAM was utilized to examine the connection between catch per unit effort (CPUE) and seamounts characteristics of yellowfin tuna in two different fishing methods. The results show that in the WCPO, the yellowfin tuna catches in the two fisheries mainly originated from seamount areas, and seamount characteristics had a highly significant effect on CPUEs of yellowfin tuna in both fisheries (P<0.001). In the longline fishery, higher CPUE occurred in seamount areas with less peak depth, roughness, base area, and seamount density as well as gentler slopes, whereas higher CPUE occurred in the purse seine fishery in seamount areas with less roughness, greater peak depth, greater base area, as well as steeper and denser slopes. In summary, we explore the mechanism of the influence of WCPO seamount characteristics on different populations of yellowfin tuna, which provides new ideas and references for further exploring the relationship between the distribution of yellowfin tuna populations and changes in resource abundance with the marine environment in the future.