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Marine Ecology Progress Series

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MEPS 353:243-254 (2008)  -  DOI:

Trophic ecology of bullet tuna Auxis rochei larvae and ontogeny of feeding-related organs

Elvira Morote1,*, M. Pilar Olivar1, Patricia M. Pankhurst2, Fernando Villate3, Ibon Uriarte3

1Instituto de Ciencias del Mar (CSIC), Paseo Marítimo de la Barceloneta 37-49, 08003 Barcelona, Spain
2School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia
3Departamento de Biología Vegetal y Ecología, Universidad del País Vasco, Campus de Leioa, Barrio Sarriena s/n, 48940 Leioa, Spain

ABSTRACT: The bullet tuna Auxis rochei, Risso 1810, is a small tuna widely distributed in tropical and temperate seas. The present study reports on the first attempt to jointly monitor diet and food selection in larvae of this species and to assess the influence of the ontogenetic development of feeding-related organs on the diet. A. rochei larvae from 2 to 7 mm long are diurnal feeders and highly active predators, with high values of feeding incidence, gut fullness and number of ingested prey items. The rate of change in prey item size in relation to larval size was higher than in other species. Only small, non-motile prey items are eaten at the onset of feeding. Rapid mouth development and the early appearance of teeth allow larvae from 3 to 5 mm long to ingest a wide range of prey. However, niche breadth decreases at 5 mm, when larvae avoid small prey items in favour of larger ones with a higher carbon content. Chesson’s selectivity index indicated that small larvae (from 2 to 3 mm long) selected a variety of small prey items, mainly copepod nauplii. Larvae measuring 3 to 5 mm selectively ate cladocerans and appendicularians, and larvae with lengths ≥5 mm preferred appendicularians and fish larvae. Precocious body development (mouth, teeth, and onset of stomach and caudal fin development) and improved visual acuity (larger lens diameter and angular cone density) are factors that contribute to the feeding success of larvae of this species.

KEY WORDS: Bullet tuna larvae · Feeding ecology · Prey selection · Ontogeny · Vision · NW Mediterranean

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Cite this article as: Morote E, Olivar MP, Pankhurst PM, Villate F, Uriarte I (2008) Trophic ecology of bullet tuna Auxis rochei larvae and ontogeny of feeding-related organs. Mar Ecol Prog Ser 353:243-254.

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