Análisis de la ecología trófica del tiburón azul (Prionace glauca) y los cambios en su alimentación a lo largo de su ontogenia
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2023
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es
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Universidad Andrés Bello
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Licencia CC
Licencia CC
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El tiburón azul es un carcarrínido pelágico que se caracteriza por un cuerpo delgado, con aletas pectorales largas y una coloración azul y blanca. Su tamaño promedio varía muy poco según su sexo y llegan a alcanzar una longitud máxima entre los 243 y 402 centímetros. Se encuentra ampliamente distribuido a nivel global entre las latitudes 62°N y 54°S. Su alimentación se basa principalmente en peces teleósteos y cefalópodos, aunque también figuran en su dieta otras especies como cetáceos, aves marinas e incluso otros tiburones.
El enfoque de esta investigación fue estudiar la ecología trófica del tiburón azul y evaluar si existían cambios en su alimentación a lo largo de su ontogenia. Para esto, se utilizaron los isótopos estables 15N y 13C como rastreadores ecológicos, donde los valores de ẟ 15N son una aproximación de la posición trófica mientras que los valores de ẟ 13C indican fundamentalmente la fuente primaria de carbono. El proceso de muestreo se llevó a cabo durante un mes en la zona de Coquimbo en el que se recolectaron 67 ejemplares. Se registró por cada uno su longitud, indicador de la edad del tiburón, y a partir de esta se clasificaron como juveniles, subadultos y adultos. Posteriormente se llevó a cabo la determinación isotópica a partir de la estructura del cristalino del globo ocular y los datos obtenidos fueron procesados en el programa R versión 4.3.2. Se aplicó la prueba de normalidad de Shapiro-Wilks, que probó la distribución normal de los datos, y se construyó un modelo lineal generalizado (GLM) en conjunto con un modelo bayesiano mixto. El GLM permitió establecer que existían variaciones significativas entre los valores isotópicos obtenidos con respecto a la longitud y, por lo tanto, con respecto a la edad de los tiburones, mientras que el modelo bayesiano mixto permitió determinar que en la composición de la dieta para este grupo de tiburones predominaron las especies de jurel para los tres estadios ontogénicos, mientras que presas que se consideraban importantes como especies de cefalópodos y atunes en cuanto a su contribución a la alimentación de este tiburón, aportaron muy poco a la dieta para los estadios ontogénicos estudiados.
The blue shark is a pelagic carcharhinid that is characterized by a thin body, long pectoral fins, and a blue and white coloration. Its average size varies truly Little depending on their sex and reach a maximum length between 243 and 402 centimeters. It’s widely distributed globally between latitudes 62°N and 54°S and it’s currently listed by the IUCN as Near Threatened, mainly due to overfishing. Their diet is mainly based on teleost fish and cephalopods, although other species such as cetaceans, seabirds and even other sharks also appear in its diet. The focus of this research was to study the trophic ecology of the blue shark and evaluate whether there were changes in its diet throughout its ontogeny. For this, the stable isotopes 15N and 13C were used as ecological tracers, where ẟ 15N values approximate the trophic position while ẟ 13C values mainly indicate the primary carbon source. The sampling process was conducted for a month in the Coquimbo area in which 67 specimens were collected. Its length was recorded for each one, an indicator of the shark's age, and from this they were classified as juveniles, subadults and adults. Subsequently, isotopic determination was conducted from the eye lens and the data obtained were processed in the R program version 4.3.2. The Shapiro-Wilks normality test was applied, which tested the normal distribution of the data, and a generalized linear model (GLM) was constructed in conjunction with a Bayesian mixing model. The GLM allowed us to establish that there were significant variations between the isotopic values obtained with respect to the length and, therefore, with respect to the age of the sharks, while the mixing model allowed to determine that in the composition of the diet for this group of sharks, mackerel species predominated for the three ontogenic stages, while prey that were considered important, such as species of cephalopods and tunas in terms of their contribution to the diet of this shark, contributed very little to the diet for the ontogenic stages studied.
The blue shark is a pelagic carcharhinid that is characterized by a thin body, long pectoral fins, and a blue and white coloration. Its average size varies truly Little depending on their sex and reach a maximum length between 243 and 402 centimeters. It’s widely distributed globally between latitudes 62°N and 54°S and it’s currently listed by the IUCN as Near Threatened, mainly due to overfishing. Their diet is mainly based on teleost fish and cephalopods, although other species such as cetaceans, seabirds and even other sharks also appear in its diet. The focus of this research was to study the trophic ecology of the blue shark and evaluate whether there were changes in its diet throughout its ontogeny. For this, the stable isotopes 15N and 13C were used as ecological tracers, where ẟ 15N values approximate the trophic position while ẟ 13C values mainly indicate the primary carbon source. The sampling process was conducted for a month in the Coquimbo area in which 67 specimens were collected. Its length was recorded for each one, an indicator of the shark's age, and from this they were classified as juveniles, subadults and adults. Subsequently, isotopic determination was conducted from the eye lens and the data obtained were processed in the R program version 4.3.2. The Shapiro-Wilks normality test was applied, which tested the normal distribution of the data, and a generalized linear model (GLM) was constructed in conjunction with a Bayesian mixing model. The GLM allowed us to establish that there were significant variations between the isotopic values obtained with respect to the length and, therefore, with respect to the age of the sharks, while the mixing model allowed to determine that in the composition of the diet for this group of sharks, mackerel species predominated for the three ontogenic stages, while prey that were considered important, such as species of cephalopods and tunas in terms of their contribution to the diet of this shark, contributed very little to the diet for the ontogenic stages studied.
Notas
Tesis (Licenciado en Biología)
Palabras clave
Tiburones, Tiburón Azul, Alimentación, Isótopos, Análisis, Chile, Coquimbo.