M. Relini

History, ecology and trends for artificial reefs of the Ligurian sea, Italy

From 1970 to the present 10 artificial reef sites have been developed in coastal waters of the Ligurian Sea, Italy. They range from Ventimiglia, in the west, to La Spezia, in the east, with the largest and best known reef complex being located in the Gulf of Genoa at Loano and consisting of 2,745 m3, about 5,200 t of material and covering a surface of 350 ha. Design and construction practices have advanced from an initial, unsuccessful effort that used automobile bodies (now banned) to current use of custom-designed concrete modules deployed systematically. Funding for reef construction has come since 1983. The earliest aim of reefs was as a physical barrier to protect habitats against illegal otter trawl fishing. Newer objectives include habitat restoration, enhancement of biodiversity and fishing catch, and research to test materials and designs for physical and ecological performance. Reefs also functions as environmental observation stations, with the invasive species Caulerpa taxifolia (Vahl) C. Agardh, being recorded on the reef at Alassio. For some Artificial Reefs (Ars), benthic organisms and fishes, settlement, biomass and development of community are recorded. In Loano AR, immersed in 1986, more than 150 algae species are recorded, more than 200 benthic animal species and 78 species (87 taxa) of fishes. Fifty-six species (61 taxa) of fishes are recorded by visual census, the others are caught only by trammel net and long line. Trammel catches at Loano are on average about 2.32 kg/100 m net. Comparisons among ARs reveal that age of the reef, location and presence of seagrass meadows are crucial for success. An indication of functional equivalence between ARs and natural rocky reefs is seen if both fish and sessile macrobenthos are compared. After 34 years of investigation a database comprising at least one hundred scientific articles based on research programs of up to 15 years, and other unpublished reports, provides information to guide future planning of reefs. On the basis of acquired experience, some management advice is suggested and the best design for the basic module in the Ligurian sea is described. The role of ARs, providing protection of coastal environment against the illegal otter trawling, nursery, microhabitat and food supply, while increasing biodiversity, biomass of benthos and fishes, and facilities for ecotourism, is outlined.

The macrofouling on offshore platforms at Ravenna

Abstract The fouling which settles on gas platform piles was studied using samples taken in 1993 from the PCWA and ANTARES platforms positioned, at 7 and 10.5 km from the shore respectively and on bottoms at 12 m and 14 m in the Adriatic Sea. For each platform a pile was chosen as representative of the macrofouling found on the whole platform. In March and September 1993 samples were obtained by scraping an area of 600 cm2 from three or four different aspects (North, East, South, West), at the same depth. Samples were taken at depths of 0.5, 5.5 and 12 m on PCWA and 0.5, 7 and 12 m on ANTARES. Photographs and video recordings taken over the whole length of the chosen pile were used for an additional description of the settlement. On both platforms the macrofouling was characterized by a dominance of mussels from sea surface to a depth of about 10 m. Near the bottom the bivalve Crassostrea gigas, barnacles, hydroids and serpulids were more important. The presence of the bryozoan Schizoporella errata (present only at ANTARES) and the zoanthid Epizoanthus arenaceus (present only at PCWA) were the main differences at this depth. The fouling, or mussel weights, of the two platforms were similar for the two seasons, even though the highest values were registered in September on PCWA (1 m) with 1561.3 g/dm2, of which 1553 g/dm2 comprised mussels. A comparison is drawn with a previous fouling experiment (which used one-year panels) carried out in 1975–76.

An offshore buoy as a small artificial island and a fish-aggregating device (FAD) in the Mediterranean

The ODAS Italia 1 oceanographic buoy is moored in the Ligurian Sea, 37 nm from Genoa, along the Genoa-Cape Corse transect (43° 48.90′ N–09° 06.80′ E), over a 1270 m deep sea bottom. The underwater portion of the buoy is 37 m long and 0.60 m in diameter, acting as a small island for colonization of fouling organisms and as a fish-aggregating device (FAD). The role of the buoy in attracting and maintaining fish assemblages was investigated by visual censuses in different seasons at depths of 0–40 m. Fish from seven families, comprising 12 species, of which three are benthic, were recorded with maximum abundance in summer. Fouling was studied from samples collected on the buoy and on immersed panels. The fouling community of the buoy consisted of 34 algae and 100 animal species, including three fish. The settlement processes of the fouling community on the panels, in particular on those exposed for over 70 months at 12 m and 33 m depth, are described based on counts of settled organisms, the covering index of each taxa and biomass assessments. On the panels, 63 species were identified. The fouling biomass, on the panel submerged for 70 months, assessed as wet weight, reached 2.8 kg/m2 at 12 m depth and 4.8 kg/m2 at 33 m depth.Observations of benthic organisms settled directly on the buoy were made between 1988 and 1989 and when the buoy was retrieved and brought back to shore on April 15, 1991 after 52 months at sea. At this time, the fouling community along the full 37 m length of the buoy was sampled, and 91 taxa, including 83 species, were identified. Several of the species present on the buoy are shallow, coastal species, some with a very short larval period. Possible ways of colonization by such species are discussed. Despite seasonal changes, the pelagic fish community was more stable over the period of 11 years of study than the benthic community settled on the buoy (that is still developing).

Feeding habits of Percnon gibbesi (H. Milne Edwards, 1853) in the Sicily Strait

The subtropical grapsid crab Percnon gibbesi (H. Milne Edwards, 1853) is one of the most recent alien decapods found in the Mediterranean, where it was discovered at Linosa (Pelagie Islands, Sicily Strait) in summer 1999. At present, the invasion of this species has been recorded in several other insular localities. We studied the feeding habits of the crab in an attempt to understand its success in the Mediterranean. The morphological characteristics of the chela, the feeding adaptations of the gastric mill and the analysis of stomach contents indicate that P. gibbesi is a strictly herbivorous species, a characteristic not shared with any other large-sized infralittoral Mediterranean crab.

Fish biodiversity in a Caulerpa taxifolia meadow in the Ligurian Sea.

Abstract The fish population of a flat marine area (near Imperia in the Ligurian Sea), depths between 4 and 8 m, colonized by the allochthonous alga Caulerpa taxifolia (Valhl) C. Agardh, was studied during a series of observations from October 1994 to October 1996. Visual censuses and catches using 200 m trammel nets were carried out. Fifty different fish species were observed, Sparidae and Labridae, with 12 and 10 species respectively, were the two most represented families. Maximum Shannon‐Weaver index obtained by censuses was 3.29 and by net catch 3.40. Abundances of Symphodus tinea and Scorpaena porcus seemed to be a characteristic of this community. A comparison with fishing data obtained in a control area without C. taxifolia, but colonized by the phanerogam Cymodocea nodosa, gave an idea of the changes produced in the fish population as a consequence of the spread of the allochthonous alga. A comparison with Mediterranean rocky environments indicated the existence of some shared qualitative charact...

Large pelagic fish, swordfish, bluefin and small tunas, in the Ligurian Sea: biological characteristics and fishery trends

This article presents a review and summary of the data on large pelagic fish, collected over the period 1990–2007, thanks to national and European Community research programmes. Swordfish are present in the Ligurian Sea at all life history stages. Time series of longline fishing catch per unit effort (CPUE) values show a good exploitation status, possibly related to the dismission of past questionable fishing technics (e.g. ‘spadare’ nets). CPUE values were also negatively related to North Atlantic oscillation: climatic factors probably had synergic effects. Bluefin is present in the Ligurian Sea with mainly schools of young fish aged 1–4 years, which feed on small pelagic fish and on the Ligurian krill Meganyctiphanes norvegica. Recent limitations on catches have severely reduced local fishing activities. Following the dismission of purse seiners, artisanal hook-based fisheries should be maintained, regardless of the length of fish caught, as a way of monitoring stock status. The two most abundant species of small tuna, Sarda sarda and Auxis rochei rochei, are present in the Ligurian Sea at all life stages. In particular, Auxis rochei rochei is a commercially neglected species which, in terms of larval occurrence, is the most abundant in the Mediterranean. Physiomorphological and genetic studies have been recently carried out in order to improve forthcoming exploitation.

Settlement on concrete blocks immersed in the Ligurian Sea (N-W Mediterranean)

Abstract Within the framework of a study on the behaviour of recycled materials in the sea, cubic concrete blocks (used as control material) were immersed at two different locations (Loano and Lavagna) in the Ligurian Sea. The study started in November 1993 and ended in December 1994. In order to gain an idea of the different settlement periods and of the subsequent evolution of the population present on the substrata, these concrete blocks were taken away for faunal analysis and replaced by new blocks every three months. Each block settlement was described, both in terms of quality (species present) and quantity (covering indices, wet weight, dry weight and ash weight). The total number of taxa found in the two localities was 53, 26 of which were common to both sites. The pattern of community development was quite similar and the one year biomass was slightly higher in Loano with 14.2 g/dm 2 of wet weight (8.3 dry weight, 6.7 ash weight) while, in Lavagna, 12.2 g/dm 2 wet weight (6.7 dry weight, 6.1 ash weight) was reached.