Abstract
Size-based dietary shifts in marine fishes assessed by stable isotopes analysis: Fish undergo significant morphological changes throughout their lives, like in the relative length of the digestive tube or the increase of mouth gape, and some of them can lead to changes in the trophic level. Studying these changes is important to understand fish trophodynamics, to verify the assumptions of size-structured trophic models and to assess community status by analyzing the size spectrum. In the present study we evaluated changes in the trophic positions of four reef-fish from northern Patagonia: Pagrus pagrus, Diplodus argentus argentus, Pinguipes brasilianus and Acanthistius patachonicus. Even though these four species share foraging areas and had similar trophic levels (trophic level ranged between 3.98 and 4.45), they exhibited specie-specific isotopic trends related to changes in body size that could be meaning different trophic behavior. While P. pagrus and A. patachonicus presented an increase in their trophic level positively correlated with body size, D. argenteus and P. brasilianus did not show any isotopic trend along ontogeny. These results highlight the importance of including the species identity in size-structured trophic models, as well as to acknowledge that size-based feeding behavior might not be ubiquitous. However, these results support the assumption that as the maximum body size of a species increases, there are more probabilities to increase trophic level with size.
Highlights
Size-based dietary shifts in marine fishes assessed by stable isotopes analysis: Fish undergo significant morphological changes throughout their lives, like in the relative length of the digestive tube or the increase of mouth gape, and some of them can lead to changes in the trophic level
In the present study we evaluated changes in the trophic positions of four reef-fish from northern Patagonia: Pagrus pagrus, Diplodus argentus argentus, Pinguipes brasilianus and Acanthistius patachonicus
Even though these four species share foraging areas and had similar trophic levels, they exhibited specie-specific isotopic trends related to changes in body size that could be meaning different trophic behavior
Summary
1. Universidad Nacional de la Patagonia San Juan Bosco, Puerto Madryn, Argentina. 2. Centro Nacional Patagónico (CONICET), Puerto Madryn, Argentina. En el presente trabajo se evaluaron los cambios en la posición trófica con respecto al tamaño corporal para cuatro especies de peces que habitan los arrecifes norpatagónicos, Pagrus pagrus, Diplodus argentus argentus, Pinguipes brasilianus y Acanthistius patachonicus. Pagrus pagrus y A. patachonicus exhibieron un aumento en el nivel trófico correlacionado con el tamaño, mientras que P. brasilianus y D. argenteus no presentaron cambios en el nivel trófico en función del tamaño corporal. Estos resultados llaman la atención sobre la necesidad de contemplar la identidad de las especies en los modelos de cadena trófica estructurados por talla, sin suponer como generalizado el cambio alimentario talla-dependiente.
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