title: Optimization of foraging and diet by the piscivorous Othos dentex (Serranidae).
abstract: The aim of this study was to determine the dietary characteristics and mouth morphology of Othos dentex and to use these data, together with in situ observations of feeding behaviour, to elucidate how foraging and diet are optimized by this piscivorous serranid. Seasonal spear and line fishing over reefs in south-western Australia yielded 426 O. dentex (total length, LT, 183-605 mm), among which the stomachs of 95 contained food. The food in the stomachs of 76 fish was sufficiently undigested to be seen to contain, almost invariably, a single fish prey, which was typically identifiable to family and often to species. The prey of O. dentex, which were measured (LT), represented 10 families, of which the Labridae and Pempheridae constituted nearly two-thirds of the prey volume. Two-way crossed analysis of similarities of volumetric data for stomach contents showed that the dietary compositions of the different length classes of O. dentex in the various seasons were significantly related to length class of prey, but not to prey family, length class within the various prey families or season. Furthermore, an inverse (Q-mode) analysis, including one-way analysis of similarities, showed that the patterns in the prey consumed by the different length classes of O. dentex in the various seasons were related more strongly to length class than prey family. The former trend is exemplified in a shade plot, by a marked diagonality of the length classes of prey with increasing predator size. The ingestion of typically a single teleost prey, whose body size increases as that of O. dentex increases, reduces the frequency required for seeking prey, thus saving energy and reducing the potential for intraspecific competition for food. The ability of O. dentex to ingest large prey is facilitated by its possession of a very large gape, prominent recurved teeth, dorsal and independently-moveable eyes, cryptic colouration and effective ambush behaviour. Othos dentex has thus evolved very cost-effective mechanisms for optimizing its foraging and diet.
authors.affiliation: Centre for Fish and Fisheries Research, Murdoch University, Murdoch, WA, 6150, Australia.
authors.forename: B
authors.initials: B
authors.lastname: French
authors.affiliation: School of Environmental and Life Sciences, University of Newcastle, P. O. Box 127, Ourimbah, NSW, 2258, Australia.
authors.forename: M E
authors.initials: ME
authors.lastname: Platell
authors.affiliation: Plymouth Marine Laboratory, Prospect Place, West Hoe, Plymouth, PL1 3DH, U.K.
authors.forename: K R
authors.initials: KR
authors.lastname: Clarke
authors.affiliation: Centre for Fish and Fisheries Research, Murdoch University, Murdoch, WA, 6150, Australia.
authors.forename: I C
authors.initials: IC
authors.lastname: Potter
mesh_terms: D000818:Animals; D049628:Body Size; D004032:Diet / Q000662:veterinary*; D005247:Feeding Behavior / Q000502:physiology*; D041981:Gastrointestinal Tract; D010473:Perciformes / Q000502:physiology*; D011235:Predatory Behavior / Q000502:physiology*; D012621:Seasons; D013021:South Australia; D014070:Tooth / Q000033:anatomy & histology; D014904:Western Australia
keywords: ambush predator; dietary composition; mouth gape; multivariate analyses; predator size; prey size