TITLE:
Diet of fish populations in posidonia oceanica meadows off the Island of Ischia (Gulf of Naples, Italy):
AUTHORS:
Valerio Zupo, Dorothea Stübing
KEYWORDS:
Fish; Food Webs; Spatial Variability; Posidonia Oceanica; Seagrass; Seasonality
JOURNAL NAME:
Natural Science,
Vol.2 No.11,
November
30,
2010
ABSTRACT: The gut contents of fish in three Posidonia oceanica meadows off the island of Ischia (Bay of Naples, Italy) were investigated. A total of 926 individual fish belonging to 28 species was sampled by bottom trawl in the leaf canopy. Labridae, Pomacentridae, Scorpaenidae, and Serranidae were the best represented families (41%, 38%, 8% and 6% of the total number of individuals, respectively). Of the 94 taxa detected in the gut contents, 42 were identified to the species level. The most common food items were decapod crustaceans (15% of the gut contents, on average), copepods (13%), amphipods (14%), brown fragments of P. oceanica (6%), and ostracods (6%). The most abundant species of labridae, Symphodus ocellatus and S. rostratus, showed a broad spectrum of prey. This generalist feeding may positively influence their numerical abundance. Seasonal variations in the diets of fish, also at prey-species level, were demonstrated. The fish taxon plays essentially a macro-carnivore trophic role. In the investigated seagrass meadows the main trophic fluxes start from plant detritus, macrophyta, and microphyta (as primary producers) towards crustacean decapods, copepods, ostracods, and gammarid amphipods (as secondary producers) to fish. A low recycling rate (4%) within the fish community was observed. Larger fish predators (e.g., Sparidae), swimming over the leaf canopy, are the main exporters to adjacent coastal systems.