Diet of fish populations in posidonia oceanica meadows off the Island of Ischia (Gulf of Naples, Italy):

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

Fish mitigate trophic depletion in marine cave ecosystems

“…Consistently with the few previous studies available 34 , 49 , 54 , 56 , we found that cave dwelling A. imberbis mainly feeds upon crustaceans, especially the amphipods. Mediterranean marine caves are characterized by the occurrence of abundant swarms of mysids 13 , 31 , 32 .…”

“…imberbis specimens caught by fishermen, with no information about the habitat type where they had been collected. Zupo and Stübing 54 caught A . imberbis in P. oceanica meadows, so in a different habitat from caves.…”

“…From this perspective, collecting information about the dietary patterns and nycthemeral movements of A. imberbis inhabiting Mediterranean marine caves is pivotal to better understanding its role and the way marine cave ecosystems function 22 . Information on the diet of cardinal fish is extremely scanty 49 , 54 , particularly on A. imberbis living in marine caves 34 .

Figure 1 School of Apogon imberbis at the entrance of a marine cave.

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Effects of fish predation on Posidonia oceanica amphipod assemblages

“…Gammarid density is also affected by predation, particularly that of I. minuta, which is a prey item of P. oceanica fishes (Labropoulou and Plaitis 1995). Despite their motility, their habit of hiding between seagrass blades (Virnstein et al 1984) and/or their use of strategies such as burrowing and infaunal tube-dwelling, gammarids are one of the most abundant food items for P. oceanica fishes (Zupo and Stübing 2010). At the HFD site, the relative availability of gammarid prey was much higher (89 %) than that of caprellid prey (11 %).…”

Occurrence of the connemarra clingfish, Lepadogaster candolii Risso, 1810 (Gobiesocidae) in the Aegean Sea (Izmir Bay, Turkey)

“…In the Mediterranean Sea, the fist record of L. candolii was a 50.4 mm male specimen captured off Bari, Italy, during an Adriatic deepsea expedition in 1894 (Ahnelt and Elvira, ). Although L. candolii is occasionally captured throughout the littoral zone along the Mediterranean, actual documentation from Bari, Italy (Ahnelt and Elvira, ); Lampedusa Island, Italy (Mazzoldi and De Girolamo, ); Ibiza Island, Spain (Patzner, ); Cyprus, Banyuls, Genova, Messina and the upper parts of Adriatic (Hofrichter and Patzner, ); Velebit Channel, Croatia (Novosel et al., ); Koper Bay, Gulf of Trieste, Slovenia (Turk et al., ); Central Black Sea, Turkey (Bat et al., ); Syrian coast (Saad, ); Gulf of Gabes, Tunisia (Bradai et al., ); Livorno, Italy (Piazzi et al., ); Ischia Island, Italy (Zupo and Stübing, ); Medes Island, Spain (Weitzmann and Mercader, ) and off Kastamonu, western Black Sea, Turkey (Dalgıç and Ceylan, ), indicates that L. candolii is more common in the central and western parts of the Mediterranean.…”