INVESTIGADORES
LUCIFORA Luis Omar
artículos
Título:
Food habits, selectivity, and foraging modes of the school shark, Galeorhinus galeus
Autor/es:
LUIS O. LUCIFORA; VERÓNICA B. GARCÍA; ROBERTO C. MENNI; ALICIA H. ESCALANTE
Revista:
MARINE ECOLOGY PROGRESS SERIES
Editorial:
Inter-Research
Referencias:
Año: 2006 vol. 315 p. 259 - 270
ISSN:
0171-8630
Resumen:
The foraging ecology of the school shark Galeorhinus galeuswas studied in Anegada
Bay, Argentina, during the seasonal occurrence of this species in Argentinean waters (October to
April) from 1998 to 2001. Of the 408 individuals examined, 168 (41.2%) had food remains in their
stomachs. The proportion of individuals with food remains was negatively correlated with total
length. In general, the diet was composed mainly of teleosts (98.5% IRI [index of relative impor-
tance]), with invertebrates and chondrichthyans as minor prey. The diet varied ontogenetically and
seasonally. Juveniles and adults differed in their consumption of invertebrates, with juveniles prey-
ing more on benthic invertebrates, mainly the octopus Octopus tehuelchus, and adults on squid.
From December to February, adults preyed mainly on benthic teleosts (almost exclusively the
Atlantic midshipman Porichthys porosissimus), while from March to April the consumption of squid
increased. A comparison of numbers of prey in stomachs with abundance of prey in the environment
in March and April showed that, in these months, juveniles selected invertebrates and demersal
teleosts and avoided pelagic teleosts and chondricthyan prey, and adults selected squid and avoided
pelagic teleosts. This indicates that, during this period, G. galeusis not an opportunistic predator. The
mean size of prey increased with increasing shark length, but even large sharks consumed small
prey. All shark sizes consumed prey fragments that were significantly larger than other prey con-
sumed whole. This indicates that G. galeusis able to overcome gape limitation by mutilating prey,
and that the ontogenetic diet shift was not due to a change in the ability to seize prey.