Trophic Ecology of Atlantic bluefin tuna (Thunnus thynnus) larvae

Feeding intensity, diet composition, selectivity, energy ingestion and dietary niche breadth of larval Atlantic bluefin tuna Thunnus thynnus were studied on the eastern (Mediterranean) spawning grounds of the species. Larval T. thynnus were collected in the Balearic Archipelago (north-west Mediterranean Sea) during 2004 and 2005 using surveys specific for larval scombrids. Larvae between 2·6 and 8·7 mm standard length (LS) are diurnal feeders, and 94% of the guts collected during daylight hours were full. The mean ±s.d. number of prey per gut was 7·1 ± 5·7, with mean ±s.d. ranging from 3·0 ± 1·6 in the smallest T. thynnus larvae to 11·1 ± 5·8 in 5·0–6·0 mm LS larvae. Up to 21 prey were found in a single larval gut (5·0–6·0 mm LS) at the end of the day. Larvae progressively selected larger prey and exhibited increased carbon content concurrent with preflexion development of feeding and locomotory structures. Larvae of 5·0–6·0 mm LS exhibited positive selection of cladocerans over other prey (Chesson's index), whereas copepod nauplii dominated the diets of earlier stages. The dietary niche breadth measured increased initially but decreased at c. 5·5 mm LS. Appendicularians were found in the diet of larger larval sizes, but no piscivory was observed. Results are discussed in light of the sparse existing data for larval T. thynnus and other larval tuna species.This work is part of the BALEARES project (CTM 2009-07944 MAR). Surveys were financed by the TUNIBAL project (REN2003-01176). We wish to express our gratitude to all the staff involved in both projects for their work in making available the information and biological samples necessary to carry out this study. A.T. was supported by a FICA-ERDÉLY research grant at Mediterranean Institute for Advanced Studies (IMEDEA).Peer Reviewe

Trophic ecology of Atlantic bluefin tuna Thunnus thynnus larvae

Publicado