FEEDING-HABITS OF YOUNG-OF-THE-YEAR GREATER AMBERJACK SERIOLA DUMERILI (RISSO, 1810) ALONG THE N/W SICILIAN COAST

A survey was carried out from July to December 1992 in the Gulf of Castellammare (N/W Sicily) in order to study the feeding habits of juveniles of the greater amberjack Seriola dumerili. Stomach content analysis showed three different phases of predation during this period, depending on the size variation of the specimens. Cluster analysis suggested prey choice differed within three size groups. Class I (individuals up to 80 mm SL) feed mainly on the zooplankton community (Copepoda and Crustacea larvae). Class II (individuals ranging from 80 to 120 mm SL) represent a transition stage in which fish continue to feed on zooplankton, but benthic and nectonic items also become important. Class I…

Distribution and diet of Marthasterias glacialis at Ustica Island MPA

Distribution and diet of Marthasterias glacialis was studied at Ustica Island MPA. We conducted observations of the asteroid along the upper infralittoral zone using random parallel transects. M. glacialis was more abundant at study sites characterized by low densities of erect algae. Most frequent prey species was a bivalve and sea urchins

Protection effect on distribution patterns of Paracentrotus lividus and Arbacia lixula in the “Plemmirio” Marine Protected Area

First estimates of density and distribution of the alien crab Percnon gibbesi (Decapoda, Percnidae) in the "Capo Gallo-Isola delle Femmine" MPA

Diet and trophic interactions of Paracentrotus lividus and Arbacia lixula in two alternative stable states of the Mediterranean rocky sublittoral community

Invasive mussels directly threat intertidal vermetid reef: some evidences from a Sicilian MPA

Biological invasions pose a great threat to natural communities. Brachidontes pharaonis is an Eritrean mussel that has accessed in the Mediterranean sea shortly after the opening of the Suez Canal. At the beginning it had a restrained distribution with small local populations along the Israeli intertidal coast. More than a hundred years later it spread westward as far as NW Sicily, colonizing some hyperaline and natural habitats. Previous studies along the Israeli coast have proved that anthropogenic habitat modi#- cations occurring on vermetid reefs may promote the colonization of this invasive mussel causing a reduction of the indigenous mussel Mytilaster minimus. This study focuses on a …

Vertical distribution of two sympatric labrid fishes in the Western Mediterranean and Eastern Atlantic rocky subtidal: local shore topography does matter

Changes in the shore topography (e.g. slope) occur at a scale of hundreds of meters in several locations in the Lusitanian and the Mediterranean Sea provinces. We tested whether differences in the bottom inclination might affect the vertical distribution patterns of two sympatric coastal labrid fishes, the rainbow wrasse Coris julis and the ornate wrasse Thalassoma pavo. Visual censuses were used to determine the distribution and abundance of these labrid species in high (‡30 ) and low (£3 ) slope rocky substrates covered by brown macroalgae and at two different depths (shallow, 4–7 m, and deep 14–20 m). Pectoral fin aspect ratio was used as an estimate of swimming performance to potentiall…

Dinamica dell’ecosistema roccioso dell’AMP “Isola di Ustica” nell’ultimo cinquantennio attraverso la conoscenza dei veterani del mare.

Integrity of predator assemblages controls the abundanceof the alien crab Percnon gibbesi

Ecosystem resistance to species invasion is considered to be related to the abundance and diversity of native species (i.e. diversity-resistance hypothesis). In particular, the integrity of predator assemblages may enhance the control of prey populations through direct and indirect interactions (e.g.: different predation strategies by different predators, facilitative interactions among predators). Depletion of predators due to overfishing is therefore expected to enhance the abundance and ultimately the spread of alien prey species. Manipulative field experiments were performed to evaluate the effects of different abundance and diversity of predator assemblages on the invasion success of t…

Le banquette di Posidonia oceanica in Sicilia occidentale: mappatura, tipizzazione e indagini sulla mesofauna associata.

Predation on sea urchin by Marthasterias glacialis (L.).

Relative role of fish vs. starfish predation in controlling sea urchin populations in Mediterranean rocky shores

In the Mediterranean, fishing bans generally allow the recovery of populations of sea urchin predators, such as the seabreams Diplodus sargus and D. vulgaris, promoting the transformation of overgrazed communities into ones dominated by erect macroalgae. However, in the marine reserve on Ustica Island (SW Italy) the opposite trend has occurred in the upper infralittoral community, and urchin barrens formed after the cessation of fishing activities. We hypothesized that (1) the natural scarcity of the 2 seabream species leads to a low predation rate on sea urchins at Ustica, and (2) predation rate varies with depth, due to differences in the predator assemblages. Tethering experiments were c…

Ruolo ecologico degli Asteroidei in due comunità dell'infralitorale superiore dell'Isola di Ustica

Gli asteroidi sono predatori che si ritrovano comunemente negli ecosistemi marini di fondo duro e mobile. Nell’Area Marina Protetta “Isola di Ustica” il divieto di raccolta del riccio edule Paracentrotus lividus nell’infralitorale superiore, ha determinato la sostituzione della comunità ad alghe fotofile erette con una comunità dominata da alghe incrostanti e ricci (barren) in gran parte dell’isola. Tre specie di asteroidi, Marthasterias glacialis, Ophidiaster ophidianus e Coscinasterias tenuispina, si ritrovano comunemente sia nell’habitat dominato dal barren che in quello dove rimangono elevate coperture ad alghe fotofile erette. Sono state studiate la distribuzione e le abitudini aliment…

Feeding behaviour of Ophidiaster ophidianus (Lmk.) (Asteroidea) in Mediterranean rocky reefs

The thermophilic Atlanto-Mediterranean purple starfish, Ophidiaster ophidianus, is a species protected under the EU’s Habitats Directive which is expanding its distribution in the northern Mediterranean areas as a consequence of global worming. The ecology of the species is largely unknown, specially for the diet. To cover this gap, the feeding habits of O. ophidianus have been studied in two different Mediterranean rocky reef areas: the southern Tyrrhenian Sea (Ustica Island, sampled in 2009) and the eastern Adriatic Sea (Molunat, sampled in 2014) by both field observations and ?13C and ?15N stable isotope analysis (SIA). SCUBA divers collected data by turning adult starfish downside-up an…

Seawater carbonate chemistry and biogenic habitat shifts under long-term ocean acidification

Experiments have shown that increasing dissolved CO2 concentrations (i.e. Ocean Acidification, OA) in marine ecosystems may act as nutrient for primary producers (e.g. fleshy algae) or a stressor for calcifying species (e.g., coralline algae, corals, molluscs). For the first time, rapid habitat dominance shifts and altered competitive replacement from a reef-forming to a non-reef-forming biogenic habitat were documented over one-year exposure to low pH/high CO2 through a transplant experiment off Vulcano Island CO2 seeps (NE Sicily, Italy). Ocean acidification decreased vermetid reefs complexity via a reduction in the reef-building species density, boosted canopy macroalgae and led to chang…

Seawater carbonate chemistry and nest guarding behaviour of a temperate wrasse

Organisms may respond to changing environmental conditions by adjusting their behaviour (i.e., behavioural plasticity). Ocean acidification (OA), resulting from anthropogenic emissions of carbon dioxide (CO2), is predicted to impair sensory function and behaviour of fish. However, reproductive behaviours, and parental care in particular, and their role in mediating responses to OA are presently overlooked. Here, we assessed whether the nesting male ocellated wrasse Symphodus ocellatus from sites with different CO2 concentrations showed different behaviours during their breeding season. We also investigated potential re-allocation of the time-budget towards different behavioural activities b…