Estructura y dinámica poblacional de Prochilodus magdalenae (Characiformes: Prochilodontidae) durante migraciones, sector río Sogamoso (2014–2023)

Abstract

Introduction: Prochilodus magdalenae (bocachico) is a key migratory species in the Magdalena River basin, with high ecological and fisheries relevance. However, its populations have declined due to overfishing and habitat degradation. This study analyzes the population dynamics of the bocachico in the Tienda Nueva - La Flor sector of the Sogamoso river during the period 2014-2023, evaluating its abundance, biomass and relationship with environmental variables. Objective: To characterize the population structure of P. magdalenae in the Tienda Nueva La Flor sector of the Sogamoso River (2014–2023), identifying patterns of abundance, biomass, body condition, and their relationship with environmental factors. Methods: A total of 47 770 individuals were analyzed from catches obtained between 2014–2023. Morphometric variables (total weight, total length, standard length), condition factor (K), and environmental parameters (flow rate, precipitation, temperature) were recorded. Statistical analyses included temporal trend evaluation, correlation analyses, and time-series modeling. Results: A significant reduction in body size was detected, with a mean standard length (LS) of 20.85 cm and a predominance of individuals < mean size at capture (TMC) (25 cm LS) (81.7 %). Biomass exhibited interannual fluctuations, with peaks during the “main spawning migration” in most years. Abundance peaked in 2019, followed by a fluctuating trend in subsequent years. The length–weight relationship indicated negative allometric growth (b = 1.864), suggesting reduced weight gain relative to length. The condition factor varied significantly among years and migration periods, with lower values in 2015–2016 and an increase until 2021. Correlations between biological and environmental variables were generally weak. Conclusions: The population structure of P. magdalenae has undergone significant changes in the last decade, with reduced average size and increased individuals < TMC (25 cm LS) captures. These findings suggest impacts of selective fishing and environmental variability. Management measures, such as minimum catch size regulations and continuous monitoring, are recommended to support the conservation of the species.