Estimación bioenergética del consumo de presas por el salmón Chinook (Oncorhynchus tshawytscha) en la zona costera centro-sur de Chile: énfasis en anchoveta y sardina común.
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Date
2026
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Universidad de Concepción
Abstract
Las invasiones biológicas por grandes depredadores piscívoros en ecosistemas marinos costeros representan una amenaza creciente, aunque aún poco cuantificada, para la biodiversidad y las pesquerías. El salmón Chinook (Oncorhynchus tshawytscha) estableció poblaciones autosustentables en cuencas del centro-sur de Chile hace casi cinco décadas, superponiéndose espacial y temporalmente con la anchoveta (Engraulis ringens) y la sardina común (Strangomera bentincki), dos especies clave que sostienen depredadores marinos nativos y pesquerías de importancia global en el Sistema de la Corriente de Humboldt.
Se desarrolló un modelo bioenergético estructurado por edades para cuantificar el consumo marino de presas durante el periodo 2014-2022 por parte de las poblaciones de salmón Chinook asociadas a cuatro sistemas fluviales del centro-sur de Chile (Imperial, Toltén, Valdivia y Bueno). El modelo integró información sobre composición de dieta, isótopos estables, densidad energética, temperatura y demografía poblacional, procedente de registros históricos de monitoreo y muestreos complementarios.
El consumo poblacional acumulado durante el período de estudio totalizó 94 515 toneladas, de las cuales sardina común (34,8%) y anchoveta (22,8%) representaron la mayor fracción. Las estimaciones anuales variaron 17 veces entre el año de menor (1 297 t en 2022) y mayor consumo (22 114 t en 2015), variación asociada principalmente con las fluctuaciones de la abundancia marina reconstruida, mientras que el consumo individual mostró una variación comparativamente menor.
Cuando se expresó en relación con la biomasa regional de referencia, el consumo modelado combinado de sardina común y anchoveta representó, en promedio, el 0,43% anual (rango: 0,05–0,82%) y permaneció por debajo del 1% en todos los años. Sin embargo, el C/B modelado específicamente para anchoveta fue mayor durante los años de elevada abundancia marina reconstruida del salmón Chinook, alcanzando el 5,3% en 2014 y el 12,6% en 2015, cuando la alta abundancia del depredador coincidió con una biomasa regional de referencia comparativamente baja de anchoveta.
Estos resultados muestran que la depredación por salmón Chinook constituye una fuente cuantificable de remoción de biomasa de presas, cuya magnitud varía marcadamente entre años. Para contextualizar esta magnitud, la fracción de biomasa consumida anualmente (C/B) se comparó con la tasa anual de explotación pesquera de referencia en el rendimiento máximo sostenible (ERMS). El C/B permaneció por debajo de ERMS en todos los años y para ambas especies (ERMS sardina = 17,3%; ERMS anchoveta = 27,2%), aunque en 2015 el C/B de anchoveta alcanzó el 46,2% de ERMS. Esta comparación dimensiona el impacto trófico directo del salmón Chinook como remoción relativa de biomasa de presas, expresándolo en una escala anual común con la explotación pesquera e identificando los años y especies en que la remoción relativa de biomasa fue mayor; sus consecuencias sobre la dinámica poblacional de las presas requieren una evaluación específica. El marco metodológico desarrollado, implementado en R mediante el paquete fb4package, es reproducible y adaptable a otras cuencas y constituye una base técnica para evaluar la posible incorporación de la depredación por salmón Chinook en marcos de gestión pesquera con enfoque ecosistémico.
Biological invasions by large piscivorous predators in coastal marine ecosystems represent a growing, yet poorly quantified, threat to biodiversity and fisheries. Chinook salmon (Oncorhynchus tshawytscha) established self-sustaining populations in rivers of south-central Chile nearly five decades ago, overlapping spatially and temporally with anchovy (Engraulis ringens) and common sardine (Strangomera bentincki), two key forage fish species that sustain native marine predators and globally important fisheries in the Humboldt Current System. An age-structured bioenergetic model was developed to quantify marine prey consumption during 2014-2022 by Chinook salmon populations associated with four river systems in south-central Chile (Imperial, Toltén, Valdivia, and Bueno). The model integrated information on diet composition, stable isotopes, energy density, temperature, and population demographics from historical monitoring records and supplementary sampling. Cumulative population-level consumption over the study period totalled 94 515 tonnes, of which common sardine (34.8%) and anchovy (22.8%) represented the largest fractions. Annual estimates varied 17-fold between the lowest (1 297 t in 2022) and highest (22 114 t in 2015) consumption years, a pattern associated with fluctuations in reconstructed at-sea abundance, whereas individual consumption varied comparatively less. When expressed relative to regional reference biomass, modelled combined consumption of common sardine and anchovy averaged 0.43% annually (range: 0.05–0.82%), and remained below 1% in every year. However, modelled anchovy-specific C/B was higher during years of elevated reconstructed at-sea Chinook salmon abundance, reaching 5.3% in 2014 and 12.6% in 2015, when high predator abundance coincided with comparatively low regional reference biomass of anchovy. These results show that predation by Chinook salmon constitutes a quantifiable source of prey-biomass removal whose magnitude varies markedly among years. To contextualize this magnitude, the annual fraction of biomass consumed (C/B) was compared with the annual reference exploitation rate at maximum sustainable yield (EMSY). C/B remained below EMSY in every year and for both species (EMSY common sardine = 17.3%; EMSY anchovy = 27.2%), although anchovy C/B reached 46.2% of EMSY in 2015. This comparison quantifies the direct trophic impact of Chinook salmon as relative prey-biomass removal, expresses it on a common annual scale with fisheries exploitation, and identifies the years and species showing the greatest relative prey-biomass removal; its consequences for prey population dynamics require specific evaluation. The methodological framework developed here, implemented in R through the fb4package, is reproducible and adaptable to other river basins and provides a technical foundation for evaluating the potential incorporation of Chinook salmon predation into ecosystem-based fisheries management frameworks.
Biological invasions by large piscivorous predators in coastal marine ecosystems represent a growing, yet poorly quantified, threat to biodiversity and fisheries. Chinook salmon (Oncorhynchus tshawytscha) established self-sustaining populations in rivers of south-central Chile nearly five decades ago, overlapping spatially and temporally with anchovy (Engraulis ringens) and common sardine (Strangomera bentincki), two key forage fish species that sustain native marine predators and globally important fisheries in the Humboldt Current System. An age-structured bioenergetic model was developed to quantify marine prey consumption during 2014-2022 by Chinook salmon populations associated with four river systems in south-central Chile (Imperial, Toltén, Valdivia, and Bueno). The model integrated information on diet composition, stable isotopes, energy density, temperature, and population demographics from historical monitoring records and supplementary sampling. Cumulative population-level consumption over the study period totalled 94 515 tonnes, of which common sardine (34.8%) and anchovy (22.8%) represented the largest fractions. Annual estimates varied 17-fold between the lowest (1 297 t in 2022) and highest (22 114 t in 2015) consumption years, a pattern associated with fluctuations in reconstructed at-sea abundance, whereas individual consumption varied comparatively less. When expressed relative to regional reference biomass, modelled combined consumption of common sardine and anchovy averaged 0.43% annually (range: 0.05–0.82%), and remained below 1% in every year. However, modelled anchovy-specific C/B was higher during years of elevated reconstructed at-sea Chinook salmon abundance, reaching 5.3% in 2014 and 12.6% in 2015, when high predator abundance coincided with comparatively low regional reference biomass of anchovy. These results show that predation by Chinook salmon constitutes a quantifiable source of prey-biomass removal whose magnitude varies markedly among years. To contextualize this magnitude, the annual fraction of biomass consumed (C/B) was compared with the annual reference exploitation rate at maximum sustainable yield (EMSY). C/B remained below EMSY in every year and for both species (EMSY common sardine = 17.3%; EMSY anchovy = 27.2%), although anchovy C/B reached 46.2% of EMSY in 2015. This comparison quantifies the direct trophic impact of Chinook salmon as relative prey-biomass removal, expresses it on a common annual scale with fisheries exploitation, and identifies the years and species showing the greatest relative prey-biomass removal; its consequences for prey population dynamics require specific evaluation. The methodological framework developed here, implemented in R through the fb4package, is reproducible and adaptable to other river basins and provides a technical foundation for evaluating the potential incorporation of Chinook salmon predation into ecosystem-based fisheries management frameworks.
Description
Tesis presentada para optar al grado de Magíster en Ciencias con mención en Pesquerías.
Keywords
Salmones, Anchoveta, Sardinas, Ecología marina, Industria pesquera