Fabio Badalamenti

Fish biomass increase after a four-year trawl ban in the Gulf of Castellammare (NW Sicily, Mediterranean Sea)

This paper deals with a year-round trawl ban implemented in 1990 in the Gulf of Castellammare (NW Sicily, Mediterranean Sea) over an area of about 200 km 2 , with the purpose of fish stock rebuilding. Artisanal and recreational fishing were permitted in the Gulf. To assess the effect of the ban on the abundance of demersal resources, CPUE from experimental trawl surveys carried out before the ban (spring 1987 and 1989) and 4 years after it was in place (spring 1994) were compared. Sampling design was based on three depth strata (10‐50, 51‐100, 101‐200 m); 21 and 30 hauls were made before and after the ban, respectively. Eleven target species (9 finfish and 2 cephalopods) as well as the total catch were used for comparisons. The total catch underwent an 8-fold increase in biomass after the four-year ban, and all the considered species underwent an increase, ranging from 1.2-fold for musky octopus (Eledone moschata) to 497-fold for gurnard (Lepidotrigla cavillone). The only decrease was for horned octopus (Eledone cirrhosa). A management strategy based on year-round trawling bans may prove useful, especially in areas where multispecies and multigear artisanal fisheries make up a large part of the fishing industry. The promising results obtained in the Gulf indicate an approach which might be practicable in areas where pre-existing data useful for traditional assessment and management are poor, or totally lacking, and where resources are already at risk of overexploitation. # 2000 Elsevier Science B.V. All rights reserved.

Patterns of algal recovery and small-scale effects of canopy removal as a result of human trampling on a Mediterranean rocky shallow community

The ecological importance of marine algae is widely known but in shallow coastal areas the composition and structure of algal communities may be affected by different human activities. Recovery from different trampling disturbances of two competing morphological groups (i.e. macroalgae and algal turfs) and effects of macroalgal canopy removal on the dominant associated fauna were examined using controlled trampling experiments. Six months after trampling disturbance was removed, the two morphological groups closely resembled control (untrampled) conditions, both in terms of cover and canopy (%). In particular, macroalgal recovery seemed to be very rapid: the higher the impact on the system the more rapid the recovery rate. In the short-term, the removal of macroalgal fronds (i.e. canopy) caused evident changes in invertebrate and crypto-benthic fish densities although these indirect effects were species-specific. Erect macroalgae are very sensitive to disturbance and even relatively low intensities of human use may be non-sustainable for this shallow assemblage. The present findings suggest some interesting options for the management of Mediterranean rocky shallow areas. This is crucial for coastal areas that are intended to be maintained in natural condition for conservation purposes.

Short-term effect of human trampling on the upper infralittoral macroalgae of Ustica Island MPA (western Mediterranean, Italy)

The short-term response of Mediterranean upper infralittoral macroalgal species to experimental human trampling was investigated. Disturbances of six different intensities were applied within the integral reserve of the Ustica Island marine protected area (Italy, Mediterranean Sea). The dominant macroalgal species Cystoseira brachicarpa v. balearica and Dictyota mediterranea were strongly affected by human trampling. Higher levels of disturbance significantly affected both algal percentage cover and canopy at an increasing rate. Three months after trampling, for both variables it was highlighted that the algal recovery from disturbance was incomplete, being significantly different among trampling intensities. The current study revealed that in the short-term it was not possible to identify critical levels of trampling that are sustainable for this shallow community.

The economic sustainability of artisanal fisheries: the case of the trawl ban in the Gulf of Castellammare, NW Sicily

Small-scale fisheries and the communities they support are often given the protection of designated fishing zones from which non-artisanal vessels are excluded. This paper looks at one example of this approach, the trawl ban introduced in the Gulf of Castellammare (NW Sicily), focussing on the economic sustainability of the artisanal fishery currently operating within the protected area. The consequences of lifting the trawl ban and how far this would jeopardise the sustainability of the artisanal fishery are explored via an analysis of the financial viability of trammel net vessels under alternative assumptions concerning catch rates. The paper also investigates fishermens attitudes towards the trawl ban and their predisposition either to remain in the fishery or to quit in the event of the ban being removed.

Molluscan assemblages associated with photophilic algae in the Marine Reserve of Ustica Island (Lower Tyrrhenian Sea, Italy)

Abstract Very few studies have addressed the effect of protection on macrozoobenthos in marine protected areas, and particularly for sites in the Mediterranean Sea. In the present study, the molluscan assemblages associated with photophilic algal communities of the Marine Reserve of Ustica Island, were investigated. A survey was carried out along transects from 1 to 15 m in depth, during the spring of 1996 at three different sites, subjected to different levels of reserve protection. Species richness and number of individuals reflected the level of protection, and both variables were significantly higher in the integral (most heavily protected) part of the reserve compared with the less well protected buffer areas. Species diversity values showed no correlation with the level of protection. The results reported here do not agree with previous findings on the ‘reserve effect’ involving large‐sized macrozoo‐benthic species. However, the data reported, together with a study on polychaetes from the same study sites, and visual census observations concerning the fish assemblage of the island may support the hypothesis that protection of piscivore and macrocar‐nivore species within the integral reserve suppresses populations of small‐sized microcarnivorous fish species, allowing ‘prey‐release’ of small benthic invertebrates.

Movements and residence time of spiny lobsters, Palinurus elephas released in a marine protected area: an investigation by ultrasonic telemetry

Marine reserves and restocking initiatives are sometimes used as a tool to enhance spiny lobster stocks. In such initiatives it is crucial to follow the movement of lobsters once they are released at sea in restocking experiments. This paper presents the results of the application of an ultrasonic telemetry system to the monitoring of 11 lobsters (90 ± 14 mm mean carapace length) released in the Capo Gallo-Isola delle Femmine Marine Reserve in north-western Sicily, central Mediterranean. The system comprised transmitters glued onto the lobster carapace, and manual as well as automated receivers to locate tagged animals. The data (i.e. number of detected signals) were tested to assess any difference in the diel activity of lobsters. The field study lasted 79 days in total. Lobsters remained in the study area for periods ranging from a few hours to the entire duration of the study. The longest distance travelled by a tagged lobster was 2.2 km. The number of signals varied significantly across the day, with the highest value recorded in the full-light hours (1000- 1500), but they were not sufficient to assess clearly the diel activity of the released lobsters. The interpretation of data suggests that: (1) released lobsters preferred a deeper habitat than that of the release site; and (2) the lobsters that reached a rough rocky area with available shelters settled there, while those that did not meet such a habitat soon moved out of hydrophone detecting range.

Artificial Reefs in the Gulf of Castellammare (North-West Sicily): A Case Study

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.

Artificial Reefs in North-West Sicily: Comparisons and Conclusions

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).

Artificial Reefs in Sicily: An Overview

Sicilian cave drawings from the Grotta del Genovese, Isle of Levanzo (west Sicily) ca. 12 000 B.C. show silhouettes of dolphins, tuna, groupers and bass which, together with remains offish (tuna, groupers, bass and others), limpets and oysters from Grotta dell Uzzo, north-western Sicily, indicate the importance of fish and shellfish in the diet of coastal populations of that time (Villari, 1992a, 1992b). Remains of turtles (Caretta caretta), tuna and sharks are evidence of fishing activity during this period (Villari, 1995).

A First Cellular Automata Model of Red Mullet Behaviour

Cellular Automata (CA) are a paradigm of parallel computing; they are good candidates for modelling and simulating acentric systems, i.e. dynamical systems, whose evolution depends exclusively on the local interactions of the constituent parts (Di Gregorio and Serra, 1999).