BackgroundThe brown croaker, Miichthys miiuy, is an economically important fish species in Korean waters. Research on the spawning ecology of M. miiuy in Korea has primarily focused on specimens from the southwestern waters, assessing parameters, such as spawning season and mature body length through histological examination. However, a comprehensive histological analysis across various body sizes during the spawning season is imperative to accurately ascertain these factors, as well as for efficient resource management amidst potential environmental variations. Therefore, this study was undertaken to investigate the spatiotemporal distribution and reproductive biology of M. miiuy in the southwestern waters of Korea.MethodsMonthly changes in gonadal maturity stages, gonadosomatic index (GSI), egg diameter, and fecundity were analyzed. Additionally, total length at sexual maturity at 50%, 75%, and 97.5%, as well as the sex ratio, were determined.ResultsM. miiuy, captured using offshore gillnets and stow nets, exhibited a seasonal migration pattern: a winter presence near Jeju Island, followed by a northward movement in spring, a summer shift to the shallow waters of Shinan, and an autumnal migration to the waters around Jeju Island for overwintering. The overall female-to-male sex ratio was 1:0.8. GSI values peaked in September and August for both sexes; however, microscopic analysis of gonadal tissue revealed a spawning period from July to September 2023, with the primary spawning season for the entire population occurring in August and September. The fork length at 50% maturity was 57.4 cm for females and 54.6 cm for males.ConclusionOverall, these results suggest an earlier shift in the spawning period of brown croakers in the southwestern waters of Korea compared to past observations. This shift is potentially attributable to higher water temperatures, increased resource levels, and alterations in the species composition of major prey items in the spawning grounds. Further research is imperative for a comprehensive understanding of the factors influencing the reproductive ecology of this important fish species.

中文翻译：

---

韩国西南水域褐黄鱼 （Miichthys miiuy） 的时空分布和生殖生物学


背景棕色黄鱼 Miichthys miiuy 是韩国水域具有重要经济意义的鱼类。韩国 M. miiuy 产卵生态学的研究主要集中在西南水域的标本上，通过组织学检查评估产卵季节和成熟体长等参数。然而，在产卵季节对各种体型进行全面的组织学分析对于准确确定这些因素以及在潜在环境变化中进行有效资源管理至关重要。因此，本研究旨在调查韩国西南水域 M. miiuy 的时空分布和生殖生物学。此外，还测定了 50% 、 75% 和 97.5% 的性成熟总长度以及性别比。结果M.使用近海刺网和收纳网捕获的 miiuy 表现出季节性迁移模式：冬季出现在济州岛附近，然后春季向北移动，夏季转移到新南浅水区，秋季迁移到济州岛周围水域越冬。总体女性与男性性别比为 1：0.8。男女的 GSI 值在 9 月和 8 月达到峰值;然而，对性腺组织的显微镜分析显示，产卵期为 2023 年 7 月至 9 月，整个种群的主要产卵季节发生在 8 月和 9 月。50% 成熟时，雌鱼的叉长为 57.4 厘米，雄鱼为 54.6 厘米。结论总体而言，这些结果表明，与过去的观察相比，韩国西南部水域褐黄鱼的产卵期变化更早。这种转变可能归因于水温升高、资源水平增加以及产卵场主要猎物物种组成的改变。为了全面了解影响这一重要鱼类生殖生态学的因素，必须进行进一步的研究。