Distribution and feeding dynamics of larval red mullet (Mullus barbatus) in the NW Mediterranean: the important role of cladocera

Abstract

The feeding habits of Mullus barbatus larvae and the horizontal and vertical distribution of larvae and their dominant prey were studied in the NW Mediterranean during the summer oligotrophic period. The water column showed marked stratification with a deep chlorophyll maximum beneath the thermocline. Horizontal and vertical distribution of larvae showed good correspondence with that of cladocera, their preferential prey from 8 mm standard length. Both groups were restricted to the upper levels of the water column, above thermocline, and were very abundant in the southern area, associated with the low salinity waters from the Ebro river runoff. Prey items consumed by the smallest size classes of larvae <8 mm SL were dominated by copepod nauplii, then diet and prey selectivity shifted towards the cladoceran Evadne spp. The amount and mean size of ingested prey increased throughout development while niche breadth remained constant. This constancy in niche breadth implies that during development larvae shift to other niches, with the replacement of nauplii by cladocerans. Results suggest that M. barbatus larvae probably depend on energy derived from the microbial food web, via their feeding on cladocera, emphasizing the key trophic role of cladocera in this oligotrophic Sea. © 2015 The Author 2015. Published by Oxford University Press. All rights reserved