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Mollusc assemblages of three concrete artificial reefs (ARs) in the Gulf of Castellammare were compared with those of two nearby natural reefs (NRs). The reefs were located in areas characterized by different degrees of water transparency, with average annual Secchi disk visibility ranging from clear (>20 m) to turbid waters (

Most carbonate rocky shores of NW Sicily are marked by a coalescence of shells of the gastropod Dendropoma in a construction that is variably developed as a response to wave impact. Here, we review all the available information on these constructions and find that the fossil reefs are reliable sea-level indicators. The thickness of the reef samples never exceeds 30–40 cm below sea-level, whereas all 14 C dates fall within a range of few centuries. Some small fragments ejected by violent sea storms date back to 2500 years cal BP. No samples older than 6200 years cal BP have been detected so far. The present distribution of Mediterranean vermetid platforms should result from a northward migration related to the long term effect of the Holocene sea surface temperature (SST) warming. Some consideration on the morphology of the reefs and the comparison with the available data point out that Dendropoma reefs are excellent biological indicators of sea-level fluctuations especially when detected and sampled in tectonically stable areas as those in NW Sicily.

Recent ecological studies have shown a strong relation between temperature, echinoids and their grazing effects on macro-algal communities. In this study, we speculate that climate warming may result in an increasingly favourable environment for the reproduction and development of the sea urchin Arbacia lixula. The relationship between increased A. lixula density and the extent of barren grounds in the Mediterranean Sea is also discussed.

Seagrass colonise new areas via the dispersion of seeds or vegetative fragments. Independent of the manner of colonization, habitat requirements need to be met for the successful establishment of seagrasses. Here we report on the colonization process of Posidonia oceanica in a highly disturbed area: a gas pipeline trench at Capo Feto (SW Sicily, Italy). A trench dredged through a P. oceanica bed was back-filled with rubble added from dump barges leading to the formation of a series of rubble mounds on the seabed. Over time, these mounds became colonised with P. oceanica. In order to understand the pattern of P. oceanica colonization, shoot density was quantified over 3 years (2001-2003) on different mound locations (crests, sides, valleys). Seagrass coalescence was observed only in valleys between mounds where shoot density averaged 133 +/- 50 shoots m(-2), while values for sides and crests were significantly lower (30.5 +/- 14 and 5.8 +/- 2.6 shoots m(-2), respectively). Although sediment accumulated on both crests and valleys, a significantly thicker sediment layer was recorded in the valleys (9.8 +/- 0.4 cm) than on crests (1.1 +/- 0.2). Plaster dissolution rate (an indicator of the hydrodynamic regime) tended to decrease from crests to valleys but even in the valleys, the currents were still higher than in the adjacent vegetated control location. This pattern was constant over time and depths. This is the first study to report on P. oceanica vegetative recruitment on artificial rubble after a disturbance event. It appears that the valleys between the rubble mounds are suitable for seagrass recruitment as sediment deposited between the rubble provides the necessary resources for plant settlement and growth. Once the seagrass patches are established, they may start a positive feedback of attenuation of currents, sediment accumulation and seagrass patch expansion.

The most notable features of the biotic colonization and fishing yield of artificial reefs are a straightforward response to local environmental conditions. When applying this assumption to the artificial reefs of north-west Sicily, the features that distinguish the reefs from each other are largely consistent with the major hydrographic characteristics of the Gulf of Castellammare, the Bay of Carini and the Gulf of Palermo. The differences in environmental conditions in the three biotopes have made it possible to compare the colonization of artificial reefs in unpolluted oligotrophic water (Bay of Carini), eutrophic water (Gulf of Palermo) and water with heavy siltation rates (Alcamo Marina artificial reef area in the Gulf of Castellammare).

Most of the plans for fish stock replenishment recently undertaken in Sicily have focused on the Gulf of Castellammare. Reasons for choosing this biotope for a restocking plan include the size of the Gulf (300 km2), the importance and traditional role of its fisheries and the existence of information describing the local marine environment. The Gulf of Castellammare is the widest bay in Sicily and fishing has always played a major role in the local economy. Today income from fishing complements that from tourism.

Floating fish aggregating devices (FADs) have long been used to attract fish in NW Sicily since antiquity. Recently, a number of changes have been made to the type of material employed to construct FADs, with the aim of increasing their effectiveness. In this paper we compare the catches made at eight experimental floating FADs (polypropylene ropes frayed at the ends) with those obtained at eight traditional FADs in the Gulf of Castellammare. A total of 672 samples were collected during summer and autumn in 1995 and 1996 at the 16 FADs using a surrounding net. Visual observations of fishes associated with the FADs were also conducted to obtain qualitative information about the spatial distribution of species. A total of 1632 specimens weighing 144 kg and belonging to eight species were caught during the survey. Seriola dumerili, Caranx crysos, C. rhonchus and Coryphaena hippurus were the most frequent and abundant species accounting for 96% of the total catch. Average fish abundance and weight, characterised by high variance, were significantly higher at the sites with experimental FADs than at the sites with traditional FADs. S. dumerili was the only species with higher catches around the experimental FADs. Some spatial and temporal variations in fish abundance and size were also detected. Younger individuals of S. dumerili were observed to show high affinity for the experimental FAD tufts., No disponible