Dinámica espaciotemporal de las fracciones adulta y juvenil de merluza común (Merluccius gayi gayi) en la zona centro sur de Chile (1997-2018): identificación de áreas de riesgo de captura de juveniles.
Loading...
Date
2025
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
Esta tesis aborda un desafío crítico para la sostenibilidad pesquera: la identificación de áreas de crianza de merluza común (Merluccius gayi gayi) y su exposición al riesgo potencial de captura incidental por la flota pesquera que opera sobre el recurso. Mediante un enfoque robusto basado en modelos espaciotemporales, se analizó la distribución y dinámica de las fracciones juvenil (edades 0 y 1), y adulta de merluza común en la zona centro-sur de Chile entre 1997 y 2018. Se utilizaron datos de captura en número por edad y área arrastrada disponibles en los cruceros de evaluación de merluza común que se realizaron anualmente desde Coquimbo a Chiloé (29°39’S–42°10’S).
A través de una combinación robusta de modelos aditivos generalizados, modelos espaciotemporales jerárquicos bayesianos y análisis de sobreposición espacial, se analizó la distribución espaciotemporal de las edades juveniles (0, 1 y 2) y del grupo plus (7+), así como su interacción con la flota industrial de arrastre de fondo.
En el primer capítulo, se examina la distribución espaciotemporal de juveniles (edades 0 y 1) en relación con factores endógenos, destacando el impacto negativo del grupo de edad más viejo (adultos de edad 7+) sobre la abundancia juvenil, como indicador de canibalismo intraespecífico potencial. Los modelos explicaron más del 75% y 95% de la variación para las edades 0 y 1, respectivamente, revelando un aumento sostenido en la abundancia de juveniles entre 2002 y 2007, y su posterior estabilización. Se demuestra que la distribución espacial juvenil está condicionada por la presencia de adultos caníbales, lo que refuerza la necesidad de proteger áreas de crianza libres de adultos mayores.
El segundo capítulo se aplicaron modelos jerárquicos bayesianos para identificar “puntos calientes” (hotspots) de ocurrencia y densidad de juveniles (edades 0, 1 y 2) y adultos (7+). Se evidencia que los juveniles se concentran en aguas someras, mientras que los adultos mayores ocupan zonas más profundas. Los hotspots de edades 0 y 1 se localizaron preferentemente entre Coquimbo y Valparaíso (29°S–33°S), mientras que los reclutas (edad 2) se distribuyen más al sur, en zonas protegidas del potencial canibalismo. Las áreas entre Corral y Maullín (40°S–42°20'S) no parecen ser aptas para la crianza de juveniles dada la baja ocurrencia y densidad. Estos patrones sugieren que los juveniles no dependen o utilizan la plataforma continental más amplia, sino de hábitats pelágicos específicos.
En el tercer capítulo, se identificaron áreas de alto riesgo de captura de juveniles al analizar la sobreposición entre hotspots y operaciones de la flota de arrastre y artesanal en el periodo 1997–2023. Se observó una alta superposición espacial entre los 33°–34°S y 36°–37°S, coincidiendo con zonas de alta ocurrencia y densidad de edades 0, 1 y 2. Además, se analizaron desplazamientos de los centros de gravedad por edad, destacando un notable corrimiento hacia el sur del centro de gravedad de la edad 0 (casi 500 km entre 1997 y 2018). Estos hallazgos evidencian una distribución dinámica del reclutamiento juvenil y la necesidad urgente de considerar la selectividad por edad y limitar a las operaciones de pesca para evitar la captura incidental de juveniles de merluza común.
En conjunto, esta tesis aporta herramientas analíticas de alto valor para la gestión espacial del recurso, ofreciendo una base científica sólida para reducir la captura incidental de juveniles, optimizar medidas de manejo adaptativo y avanzar hacia una pesquería sustentable de Merluccius gayi gayi en Chile.
This thesis addresses a critical challenge for fisheries sustainability: identifying nursery areas for the hake (Merluccius gayi gayi) and their exposure to the potential risk of incidental catch by the fishing fleet operating on the resource. Through a robust approach based on spatiotemporal models, the distribution and dynamics of juvenile fractions (ages 0 and 1) and adult hake were analyzed in the south-central zone of Chile between 1997 and 2018. Data on catch in numbers by age and trawled area from the annual hake assessment surveys conducted from Coquimbo to Chiloé (29°39'S–42°10'S) were used. Through a robust combination of generalized additive models, Bayesian hierarchical spatiotemporal models, and spatial overlap analysis, the spatiotemporal distribution of juvenile ages (0, 1, and 2) and the plus group (7+) was analyzed, as well as their interaction with the industrial bottom trawl fleet. In the first chapter, the spatiotemporal distribution of juveniles (ages 0 and 1) is examined considering endogenous factors, highlighting the negative impact of the older age group (age 7+ adults) on juvenile abundance as an indicator of potential intraspecific cannibalism. The models explained more than 75% and 95% of the variation for ages 0 and 1, respectively, revealing a sustained increase in juvenile abundance between 2002 and 2007, followed by stabilization. It is demonstrated that juvenile spatial distribution is conditioned by the presence of cannibalistic adults, reinforcing the need to protect nursery areas free of older adults. In the first chapter, the spatiotemporal distribution of juveniles (ages 0 and 1) is examined considering endogenous factors, highlighting the negative impact of the older age group (age 7+ adults) on juvenile abundance as an indicator of potential intraspecific cannibalism. The models explained more than 75% and 95% of the variation for ages 0 and 1, respectively, revealing a sustained increase in juvenile abundance between 2002 and 2007, followed by stabilization. It is demonstrated that juvenile spatial distribution is conditioned by the presence of cannibalistic adults, reinforcing the need to protect nursery areas free of older adults. The third chapter identified high-risk areas for juvenile catch by analyzing the overlap between hotspots and operations of the trawl and artisanal fleets from 1997–2023. High spatial overlap was observed between 33°–34°S and 36°–37°S, coinciding with areas of high occurrence and density of ages 0, 1, and 2. Additionally, shifts in the centers of gravity by age were analyzed, highlighting a notable southward shift in the center of gravity for age 0 (almost 500 km between 1997 and 2018). These findings demonstrate a dynamic distribution of juvenile recruitment and the urgent need to consider age selectivity and limit fishing operations to avoid the incidental catch of juvenile South Pacific hake. Overall, this thesis provides high-value analytical tools for spatial resource management, offering a solid scientific basis to reduce the incidental catch of juveniles, optimize adaptive management measures, and move toward a sustainable fishery of Merluccius gayi gayi in Chile.
This thesis addresses a critical challenge for fisheries sustainability: identifying nursery areas for the hake (Merluccius gayi gayi) and their exposure to the potential risk of incidental catch by the fishing fleet operating on the resource. Through a robust approach based on spatiotemporal models, the distribution and dynamics of juvenile fractions (ages 0 and 1) and adult hake were analyzed in the south-central zone of Chile between 1997 and 2018. Data on catch in numbers by age and trawled area from the annual hake assessment surveys conducted from Coquimbo to Chiloé (29°39'S–42°10'S) were used. Through a robust combination of generalized additive models, Bayesian hierarchical spatiotemporal models, and spatial overlap analysis, the spatiotemporal distribution of juvenile ages (0, 1, and 2) and the plus group (7+) was analyzed, as well as their interaction with the industrial bottom trawl fleet. In the first chapter, the spatiotemporal distribution of juveniles (ages 0 and 1) is examined considering endogenous factors, highlighting the negative impact of the older age group (age 7+ adults) on juvenile abundance as an indicator of potential intraspecific cannibalism. The models explained more than 75% and 95% of the variation for ages 0 and 1, respectively, revealing a sustained increase in juvenile abundance between 2002 and 2007, followed by stabilization. It is demonstrated that juvenile spatial distribution is conditioned by the presence of cannibalistic adults, reinforcing the need to protect nursery areas free of older adults. In the first chapter, the spatiotemporal distribution of juveniles (ages 0 and 1) is examined considering endogenous factors, highlighting the negative impact of the older age group (age 7+ adults) on juvenile abundance as an indicator of potential intraspecific cannibalism. The models explained more than 75% and 95% of the variation for ages 0 and 1, respectively, revealing a sustained increase in juvenile abundance between 2002 and 2007, followed by stabilization. It is demonstrated that juvenile spatial distribution is conditioned by the presence of cannibalistic adults, reinforcing the need to protect nursery areas free of older adults. The third chapter identified high-risk areas for juvenile catch by analyzing the overlap between hotspots and operations of the trawl and artisanal fleets from 1997–2023. High spatial overlap was observed between 33°–34°S and 36°–37°S, coinciding with areas of high occurrence and density of ages 0, 1, and 2. Additionally, shifts in the centers of gravity by age were analyzed, highlighting a notable southward shift in the center of gravity for age 0 (almost 500 km between 1997 and 2018). These findings demonstrate a dynamic distribution of juvenile recruitment and the urgent need to consider age selectivity and limit fishing operations to avoid the incidental catch of juvenile South Pacific hake. Overall, this thesis provides high-value analytical tools for spatial resource management, offering a solid scientific basis to reduce the incidental catch of juveniles, optimize adaptive management measures, and move toward a sustainable fishery of Merluccius gayi gayi in Chile.
Description
Tesis presentada para optar al grado de Doctor en Ciencias con mención en Manejo de Recursos Acuáticos Renovables
Keywords
Merluza chilena, Recursos pesqueros, Ecología marina