An Assessment of the Population Structure and Stock Dynamics of Megalobrama skolkovii During the Early Phase of the Fishing Ban in the Poyang Lake Basin

The ten-year fishing ban on the Yangtze River aims to restore aquatic biodiversity and rebuild fishery resources. Megalobrama skolkovii, a key species in the basin, was investigated using 2024 data to provide a preliminary assessment of its population structure, stock dynamics, and early recovery. Age analysis (n = 243) showed that 1–6-year-olds were dominated by fish aged 3 (35%), with few older than 4, indicating moderate structural truncation. Growth parameters modeled by the von Bertalanffy Growth Function yielded L∞ = 61.89 cm and k = 0.25 year−1, with a weight–growth inflection age of 4.4 years. Natural mortality (M = 0.48 year−1) was estimated using Pauly’s empirical formula, and total mortality (Z = 0.55 year−1) was estimated from the catch curve analysis. While fishing mortality (F) was statistically indistinguishable from zero, a plausible low-intensity fishing scenario was explored to assess potential impacts of residual activities. Length-based indicators (LBIs) showed Pmat = 46.05%, Popt = 9.51%, and Pmega = 6.88%, suggesting reproductive recovery but incomplete structural restoration. These preliminary findings reveal an asymmetrical recovery trajectory, whereby physiological improvements and enhanced recruitment have occurred, yet full structural restoration remains incomplete. This underscores the need for continued, long-term conservation and monitoring to support population resilience.