AUTHOR=Yu Zeshu , Wong Marty Kwok-Shing , Inoue Jun , Ahmed Sk Istiaque , Higuchi Tomihiko , Hyodo Susumu , Itoh Sachihiko , Komatsu Kosei , Saito Hiroaki , Ito Shin-ichi 

TITLE=Environmental DNA in the Kuroshio reveals environment-dependent distribution of economically important small pelagic fish

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1121088

DOI=10.3389/fmars.2023.1121088

ISSN=2296-7745

ABSTRACT=Small pelagic fishes constitute large proportions of fisheries and are important components linking lower and higher trophic levels in marine ecosystems. Many small pelagic fishes in the Northwest Pacific spawn upstream in the Kuroshio and spend their juvenile stage in the Kuroshio Front area, indicating that the Kuroshio Current system impacts their stock fluctuations. However, the distribution of these fish relative to the Kuroshio has not been determined due to dynamic spatio-temporal fluctuations of the system. Here, the recent development of environmental DNA (eDNA) monitoring enabled us to investigate the distribution patterns of four economically important small pelagic fishes (Japanese sardine Sardinops melanostictus, Japanese anchovy Engraulis japonicus, chub mackerel Scomber japonicus, and blue mackerel Scomber australasicus) in the Kuroshio Current system. The influence of environmental factors, such as sea water temperature, salinity, oxygen concentration, chlorophyll-a concentration, and prey fish on the occurrence and quantity of target fish eDNA was analyzed using generalized additive models. Sea water temperature was confirmed as important, especially for the distribution of Japanese sardine and Japanese anchovy, whereas the distribution pattern of chub mackerel and blue mackerel was greatly influenced by the quantity (represented by eDNA quantity) of Japanese sardine and Japanese anchovy (especially potential prey fish: Japanese anchovy). In addition, among the samples collected during cruises that crossed the Kuroshio, we found that the four target fish species could be observed in areas on the inshore side or around the Kuroshio axis, while they were hardly found on the offshore side. Based on eDNA data, we succeeded in revealing detailed spatial distribution patterns of small pelagic fishes in the Kuroshio Current system and hypothesized predator–prey relationships influence their distribution in small pelagic fish communities.