Seasonal Catch Dynamics and Spawning Patterns of East Asian Common Octopus Octopus sinensis d'Orbigny, 1834 in Deukryang Bay, Korea

The seasonal catch dynamics and spawning patterns of Octopus sinensis (d'Orbigny, 1834) in Deukryang Bay, Korea, were investigated to make informed sustainable resource management more efficient. Following the analysis of 2023 catch data, significant fluctuations associated with the fishing closure periods were revealed and were characterized by increased catch volumes postclosure and a notable influx of 50% maturity specimens (<549.5 g) in September and October. Heatmap cluster analysis identified distinct groupings by year and month, with peak catches recorded between July and September 2020. These patterns likely reflect interactions among environmental factors, fishing efforts, reproductive activities, and habitat suitability. The spawning season extended from April to August, with bimodal peaks in April–May and July–August, influenced by water temperature fluctuations. Sex ratios exhibited a significant male bias. Logistic regression modeling estimated the 50%, 75%, and 97.5% maturity weights at 549.5, 887.7, and 1,677.1 g, respectively. The postclosure rise in juvenile prevalence necessitates the implementation of a minimum catch weight regulation to safeguard this vulnerable life stage and promotes sustainable management of O. sinensis populations.