Seasonal variation in fish school spatial distribution and abundance under the Kuroshio regular pattern and the large meander in Suzu coastal waters

Abstract

The Kuroshio Current can take two paths; usually it follows the regular pattern but occasionally it follows a pattern known as the large meander. In this study, we investigated the abundance of fish that migrate to coastal waters and the spatial distribution of fish schools under both Kuroshio patterns in Suzu district, Kochi prefecture, where the set net is the main fishery industry. We clarified the seasonal variation in the density and distribution of fish schools using a quantitative echo sounder. The effects of the Kuroshio large meander (LM) depended on the season. There was no effect of current pattern in summer or autumn, but in winter and spring the LM altered the marine environment and fish distributions. Cold water masses were formed in the survey area during winter and spring during the LM, and the water temperature dropped significantly compared with during the Kuroshio non-large meander (NLM). This altered the fish species and the distribution of fish schools in the survey area. The catches of Japanese horse mackerels (Trachurus japonicus) and Yellowtails (Seriola quinqueradiata) were much higher during the LM compared with those during the NLM. Unlike these two species, the small-sized pelagic fishes in spring has decreased significantly during the LM.

Evaluation of the Effects of Environmental Factors on Seasonal Variations in Fish Diversity on a Coastal Island in Western Japan

“…Another species, Seriola quinqueradiata (yellowtail), which is an oceanodromous species, undergoes a northward migration in its early life stages. This migration to recruit marine waters occurs from autumn to early winter [86]. Our study revealed a similar trend in which the yellowtail migrated to the shallow coastal shoreline as the water temperature declined during the autumn survey.…”

Mixing Dynamics Within the Kuroshio Area Are Reflected in Dissolved Inorganic Radiocarbon Values

“…The upwelling induced by cold-core cyclonic eddies can significantly impact Japan's climate through coastal air-sea interactions (Sugimoto et al, 2020(Sugimoto et al, , 2021. It also influences biological production and local fisheries by re-stratifying the surface seawater through eddies (Kobari et al, 2020;Lizarbe Barreto et al, 2021;Zhu et al, 2021) and microscale turbulent mixing near the Kuroshio front (Nagai et al, 2015(Nagai et al, , 2017(Nagai et al, , 2019Uchiyama et al, 2017). Conversely, downwelling induced by warm-core anticyclonic eddies can suppress upper-ocean productivity (Uchiyama et al, 2017).…”

Anomalous Nutricline Drives Marked Biogeochemical Contrasts During the Kuroshio Large Meander

“…As of July 2023, this LM event has lasted for 6 years, which has become the longest ever recorded LM since a consistent observation by the Japan Meteorological Agency (JMA) started in the 1960s (Qiu & Chen, 2021). The ongoing LM has received much media attention in Japan, as it has been revealed to trigger extratropical cyclones with extreme rainfall (Hirata et al., 2019; Tochimoto & Iizuka, 2022), cause discomfort in summer over the greater Tokyo metropolitan area (Sugimoto et al., 2021), and modify the seasonal abundance and distribution of commercial fish (Chang et al., 2019; Zhu et al., 2021).…”