Re-Evaluation of Life History Traits of Sandfish (Arctoscopus japonicus) in Eastern Korean Waters

The sandfish (Arctoscopus japonicus) is an important fishery resource in the East/Japan Sea; however, its stock has recently declined sharply. Most ecological studies were conducted before the mid-2000s, limiting our understanding of recent ecological changes under rapidly changing environmental conditions. We aimed to analyze recent ecological characteristics of sandfish, including growth, maturation, and feeding ecology, in eastern Korean waters. Sandfish samples collected between 2021 and 2024 were analyzed. Age and growth were estimated using otolith-based analyses and the von Bertalanffy growth function. Maturation characteristics were evaluated using gonadosomatic index and maturity-stage analyses, and feeding ecology was assessed through stomach content analysis. Younger individuals (aged 1–2 years) exhibited larger body sizes than previously reported, whereas older individuals (3–5 years) exhibited relatively smaller body sizes. The peak spawning period occurred from December to January, indicating a delay in spawning compared with earlier studies. The length at 50% maturity was estimated at 16.3 cm, corresponding to 1.72 years. Euphausiacea and Amphipoda were the dominant prey items. These findings provide updated baseline information on recent ecological changes in sandfish populations and may support future stock assessment and fisheries management. Continued long-term monitoring is needed to better understand environmental influences on sandfish ecology.