Stock status of Tylosurus imperialis in the İskenderun Bay at the northeastern Mediterranean based on data-limited assessment methods

Abstract

This study evaluated the stock status of Tylosurus imperialis in İskenderun Bay (northeastern Mediterranean Sea) using monthly length-frequency data collected between April and November 2022. Growth parameters were estimated using the Electronic Length Frequency Analysis (ELEFAN) approach implemented in the TropFishR framework. The von Bertalanffy Growth Function parameters were estimated as L_∞ = 127 cm, k = 0.56 year^-1, and t₀ = -0.60 year^-1, with a growth performance index (Φ′) of 3.95. Gear selectivity analysis estimated a length at first capture (L₅₀) of 76 cm, corresponding to approximately 1.64 years of age. Length-based cohort analysis indicated considerable variation in fishing mortality among size classes, with the highest exploitation observed around 83 cm. Estimated total mortality (Z = 1.81 year^-1) and natural mortality (M = 0.54 year^-1) yielded a fishing mortality of F = 1.27 year^-1 and an exploitation rate of E = 0.69. Although fishing mortality was below the estimated F_0.1 reference point, the exploitation rate exceeded the precautionary threshold (E_0.5 = 0.55). Yield-per-recruit analysis suggested an optimal length at first capture close to the current estimate (76 cm) and indicated limited potential yield gains under increased fishing effort. While the results suggest that the stock may be experiencing relatively high exploitation pressure, these findings should be interpreted with caution given the data-limited nature of the assessment. Nevertheless, the study provides the first stock assessment information for T. imperialis in the northeastern Mediterranean and offers a basis for future monitoring and management efforts.