Growth and year-class dynamics of the Japanese silver pomfret Pampus punctatissimus: Correlation between salinity and recruitment

Abstract

Pampus punctatissimus (Perciformes: Stromateidae) is a semi-anadromous fish that typically inhabits the continental shelf but depends on estuarine environments for reproduction. This species represents an important fishery resource in the Western Pacific. However, critical knowledge gaps remain regarding its population parameters and recruitment dynamics, which are crucial for its stock management. In this study, we aimed to investigate the longevity, growth, and year-class strength via otolith analysis of P. punctatissimus specimens collected from Ariake Bay—a key reproductive area for this species—and its surrounding waters. The validity of age estimation based on whole otoliths differed between sexes and was nearly completely invalid for males. The maximum observed age based on sectioned otoliths was 13 years, exceeding the previously reported maximum age for a congener by a factor of more than two. Growth exhibited significant sexual dimorphism: females reached 3.8 kg, whereas males reached 1.2 kg. Consequently, nearly all specimens weighing more than 1 kg were female. Year-class strength fluctuated significantly, revealing a recruitment failure in 2017. The back-calculated fish length revealed density-dependent growth during the first year of life, implying that stock abundance was limited by the size of nursery habitats. Variations in year-class strength were associated with salinity in the reproductive area, with higher salinity conditions inhibiting recruitment success. The study suggests salinity in reproductive areas as a key driver of recruitment variability in P. punctatissimus, underscoring the need to protect estuarine and nursery habitats for population sustainability.