Effects of body size, age and maturity stage on diet in a large shark: ecological and applied implications

Ecological Research - Tập 24 Số 1 - Trang 109-118 - 2009
Luis O. Lucifora1, Verónica B. García1, Roberto Carlos Menni2,3, Alicia H. Escalante2,4, Natalia M. Hozbor5
1Department of Biology, Dalhousie University, 1355 Oxford Street, Halifax, NS B3H 4J1, Canada
2Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
3Departamento Científico Zoología Vertebrados Museo de La Plata Paseo del Bosque s/n La Plata B1900FWA Argentina
4Departamento de Biología Universidad Nacional de Mar del Plata Funes 3250, Segundo Piso Mar del Plata B7602AYJ Argentina
5Instituto Nacional de Investigación y Desarrollo Pesquero Paseo Victoria Ocampo s/n Mar del Plata B7602HSA Argentina

Tóm tắt

Abstract

Ontogenetic diet shifts are a widespread phenomenon among vertebrates, although their relationships with life history traits are poorly known. We analyzed the relative importance of body size, age and maturity stage as determinants of the diet of a marine top predator, the copper shark, Carcharhinus brachyurus, by examining stomach contents using a multiple‐hypothesis modeling approach. Copper sharks shifted their diet as size and age increased and as they became sexually mature, incorporated larger prey as they grew, and had a discrete shift in diet with body size, with only individuals larger than ≈200 cm total length able to prey on chondrichthyans. Body size was the most important trait explaining the consumption of chondrichthyans, while age determined the consumption of pelagic teleosts. Pelagic teleosts were consumed mostly by medium‐aged sharks, a result, probably, of a risk‐reducing feeding strategy at young ages coupled with either a senescence‐related decline in performance or a change in sensory capabilities as sharks age. Copper sharks of all sizes were able to cut prey in pieces, implying that gape limitation (i.e., the impossibility of eating prey larger than a predator's mouth) did not play a role in producing the diet shift. Our results suggest that, contrary to the current practice of setting minimum but not maximum size limits in catches, any plan to conserve or restore the ecological function of sharks, through their predatory control of large prey, should aim to maintain the largest individuals.

Từ khóa


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Ecological Research

Tập 24 Số 1

109-118

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