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MEPS prepress abstract   -  DOI:

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

Taiki Fuji*, Shin-Ichiro Nakayama, Midori Hashimoto, Hiroomi Miyamoto, Yasuhiro Kamimura, Sho Furuichi, Kazuhiro Oshima, Satoshi Suyama

*Corresponding author:

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