Feeding habits of the Magellan skate: effects of sex, maturity stage, and body size on diet |
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Authors: | Santiago A Barbini Lorena B Scenna Daniel E Figueroa María B Cousseau and Juan M Díaz de Astarloa |
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Institution: | (1) Laboratorio de Ictiolog?a, Departamento de Ciencias Marinas, Universidad Nacional de Mar del Plata, Funes 3350, Mar del Plata, B7602AYL, Argentina;(2) Comisi?n de Investigaciones Cient?ficas del Gobierno de la Provincia de Buenos Aires (CIC), Calle 526 e/10 y 11, La Plata, B1906APN, Argentina;(3) Consejo Nacional de Investigaciones Cient?ficas y T?cnicas (CONICET), Av. Rivadavia 1917, Ciudad Aut?noma de Buenos Aires, C1033AAJ, Argentina |
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Abstract: | The aim of this study was to evaluate the effects of sex, maturity stage, and body size on the diet of the Magellan skate,
Bathyraja magellanica, in the Southwest Atlantic off Argentina, by examining stomach contents using a multiple hypothesis modeling approach. Relationships
between the number of prey and sex, maturity stage, and total length (TL) were assessed by built generalized linear models
(GLM). Furthermore, we tested whether there was a threshold size at which B. magellanica started or quit consuming a given prey. The overall diet of B. magellanica was mainly consisted of teleosts, followed by amphipods, isopods, and decapods. Ontogenetic diet shifts were independent
of sex and maturity stage. However, discrete shifts in diet with TL were found, with individuals larger than 554 and 623 mm
TL ceasing to consume amphipods and isopods, respectively. The consumption of teleosts progressively increased with increasing
predator size. Likewise, ontogenetic shifts in foraging behavior were also observed with smaller individuals showing specialization
on amphipods with larger specimens consuming teleosts. These results confirm that ontogenetic shifts in diet of B. magellanica are more a function of predator size rather than any other life-history traits. We propose that these food shifts are probably
related to morphological limitations and abilities associated with feeding habits of skate, so when specimens of B. magellanica reach an optimum body size, they may have access to higher quality trophic resources. Our results suggest that evaluating
the importance of life-history stages on the feeding habits of a species is essential for understanding how that species exploits
food resources, which, in turn, is an important factor in developing a suitable plan of marine ecosystem conservation. |
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