the 22nd Pacific−Asian Marginal Seas meeting (PAMS)

The Japanese sardine Sardinops melanostictus exhibits pronounced multi-decadal fluctuations in stock abundance. During the high-stock period of the 1980s, a major spawning ground existed in the Satsunan area of southern Japan; however, this spawning ground disappeared during the stock decline in the 1990s. Since 2015, we have conducted larval monitoring surveys of small pelagic fishes in this region, and in March 2023 we detected Japanese sardine larvae for the first time. This study aims to elucidate the processes of spawning and nursery ground formation of Japanese sardine during the current stock-increasing phase. We investigated the occurrence, growth, and feeding requirements of Japanese sardine eggs and larvae in the Satsunan area. Eggs and larvae were collected at eight stations in the mouth of Kagoshima Bay and adjacent waters from 2023 to 2025, using a twin NORPAC net for eggs and an ORI net for larvae. Abundance was estimated for each station, and larval growth and food requirements were analyzed. Eggs and larvae were consistently observed in the coastal waters in March of each year. The highest abundance was recorded in March 2025, reaching 58,260.32 and 455.3 individuals per 1,000 m³ for eggs and larvae, respectively. In 2024, the estimated larval mortality rate was 11.3%. The weight-specific growth coefficient and daily ration were estimated at 0.24 d⁻¹ and 85.0% of body dry weight, respectively. These results indicate that the Satsunan area has re-emerged as an important spawning and nursery ground for S. melanostictus, potentially contributing to the recruitment of the Pacific stock.

Egg,larvae,growth,Sardinops melanostictus,Satsunan