Biological interactions potentially alter the large-scale distribution pattern of the small pelagic fish, Pacific saury Cololabis saira

We aimed to understand the effect of biological interactions on distribution small pelagic fishes. Surveys were conducted during 2003-2019 using sea surface trawl nets in western and central North Pacific Ocean, covering an area between 143° E 165° W, estimate distributions 4 fishes: saury Cololabis saira , Japanese sardine Sardinops melanostictus chub mackerel Scomber japonicus anchovy Engraulis . These species are potential competitors, as they all occupy a similar niche. was abundant 2003-2012, while 2013-2019. Only distributed throughout survey area, others occurred within west 180° longitude (WA). its competitors showed adjacent distributions, with slight overlap along temperature gradients WA. This pattern remained even when expanded colder waters increased abundance after 2013, resulting shift period high densities sardine. Such not observed east longitude, where no observed. results suggest possibility that such inter-species competition can be important factor determining