The small yellow croaker (Larimichthys polyactis) is a commercially important fishery species in China, but limitations in data availability and temporal continuity continue to constrain comprehensive stock assessment. This study integrates three length-based approaches—LB-SPR, LBB, and LIME—to evaluate the stock status from period-specific and interannual perspectives. First, LB-SPR and LBB were applied to length-composition data from four survey cruises conducted between 2019 and 2024 to characterize fishing pressure, spawning potential, relative biomass, and catch length structure. Both approaches indicated severe overexploitation, with spawning potential and relative biomass below commonly used biological reference points. Sensitivity analyses showed that LB-SPR estimates were jointly affected by asymptotic length (L_∞) and M/K, whereas LBB was more sensitive to M/K. Building on this assessment, LIME was applied to length-composition data from six survey years between 2018 and 2025 to compare interannual variation in recruitment, fishing mortality, spawning potential ratio, and relative spawning biomass. Preliminary results revealed marked differences among years, while the overall pattern continued to indicate high fishing pressure and low spawning potential. Monte Carlo simulations further identified natural mortality (M) as the dominant source of uncertainty for several LIME outputs. Collectively, the three assessment methods indicate that the small yellow croaker stock is severely overexploited, with key indicators suggesting that the stock is approaching or may already have reached a state of collapse. By combining period-specific stock diagnosis, multi-year comparison, and model-specific sensitivity analyses, this framework provides a more robust scientific basis for stock recovery and adaptive management in the Zhoushan Fishing Ground.