Vegetated Habitats Trophically Support Early Development Stages of a Marine Migrant Fish in a Coastal Lagoon

Understanding the trophic ecology of early developmental stages of commercial fish species migrating between sea and coastal lagoons is crucial to effective management of nursery habitats and resulting resources. While most information on diet shift of the gilthead seabream Sparus aurata comes from studies in experimental conditions, here we investigated the trophic niche dynamics of post-larvae, juveniles and sub-adults in natural environment, hypothesising that habitat and resources use of marine and lagoonal sites will exhibit strong relationship with ontogeny of the species. Carbon and nitrogen stable isotopes showed evidence of a clear shift in the trophic niche features, trophic position and trophic pathways supporting S. aurata during growth. Main differences occurred between post-larvae and juveniles/sub-adults, perfectly matching their diet shift from zooplanktivorous to zoobenthivorous habits. The wider trophic niche of juveniles exploiting the variety of resources within the lagoon, compared to the narrower niche of marine post-larvae demonstrates the importance of the trophic role of the lagoon as nursey ground, where aquatic macrophytes (seagrasses and macroalgae) provide the main trophic support as sources of organic matter.