Stock Assessment of Tilapia (Oreochromis aureus) in a Mexican Reservoir Using Data-Limited Methods: A Multi-Model Approach

The Tilapia (Oreochromis aureus) sustains more than 90% of the fishery value and volume in the Vicente Guerrero Reservoir (VGR), Northeast Mexico, but stock status is uncertain due to lack of assessments. A total of 1,792 individuals (2020-2021) were analyzed. Von Bertalanffy growth, total (Z), natural (M) and fishing (F) mortality, and exploitation rate (E) were estimated. Under a data-limited framework, four complementary approaches were applied: the LBB model, length-based indicators, empirical reference points, and ecological risk assessment. Growth was negatively allometric (b=2.89). Estimated parameters were: L∞=464 mm, K=0.2275 yr⁻¹, Z=3.591 yr⁻¹, M=0.3894 yr⁻¹, F=3.302 yr⁻¹, E=0.892. The LBB model estimated a relative biomass B/B₀=0.057 (95% CI: 0.042-0.072) and an F/M ratio of 8.48. Only 7.5% of individuals exceeded maturity length, 4.8% were at optimal length, and 2.6% were mega-spawners. Estimated fishing mortality exceeded the reference points (F_MSY=0.339 yr⁻¹; F_limit=0.508 yr⁻¹; F_crash=0.678 yr⁻¹) by 9.7, 6.5, and 4.9 times, respectively, classifying the stock as extreme high risk. The O. aureus stock in VGR is in biological collapse (B/B₀=5.7%; F/M=8.48). Increasing minimum capture length to at least 290 mm and reducing fishing effort by 80-90% is urgently required. The convergence of independent methods validates data-limited approaches for artisanal fisheries.