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An introduction to Mediterranean deep-sea biology* - page 20 / 32

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a high commercial value, while others, such as the greater forkbeard (Phycis blennoides), rockfish (Helicolenus dactylopterus) and the golden shrimp (Plesionika spp.), are less valuable and many others are completely discarded. In the deeper range the main catch families are composed of Moridae (Mora moro) and Alepocephalidae (Alepocephalus rostra- tus) of large size or Macruridae (Coelorhynchus coelorhynchus, Trachyrhynchus scabrus, Hymeno- cephalus italicus, Chalinura mediterranea, Nezumia aequalis) of medium size. High biomasses of these species are detected between 900 and 1300 m (Rucabado et al., 1991; Stefanescu et al., 1992; Morales-Nin et al., 2003; Cartes et al., 2004; Mas- sutí et al., 2004; Moranta, et al., 2004), but no fish- ery is carried out at the moment at these depths.

Central Mediterranean fisheries

Deep-water species in the central Mediterranean are mostly exploited by the Italian fleet, which is composed of typical Mediterranean boats and is almost exclusively artisanal in structure, except for some areas (e.g. the Sicilian Channel) where larger trawlers operate on a more industrial scale. Most of the vessels are recorded as multiple-gear vessels and are generally of small gross tonnage and smaller than 12 m in length (COM, 2002). Most of the trawlers are located in the Sicily Channel and in the South Adriatic Sea. However, in this latter basin deep-water fishing is less important than in the coastal one.

Italian bottom trawlers can share fishing activity throughout the year (in many cases during the same day) both on red shrimps and on shallower species, such as deep-water shrimp (Parapenaeus lon- girostris), Norway lobster and hake, according to the varying availability of these resources. For this reason, it is difficult to quantify the effective fishing effort targeting specific deep-water species. The proportion of the different species varies largely among the basins. From official national statistics (ISTAT), during the past decade the total Italian landings of “red shrimps” showed an oscillating trend between 3000 and 6000 t. However, apart from the low reliability of these data, several species are grouped within the same commercial category of “red shrimps” (A. antennatus, A. foliacea, P. martia, other pandalids, etc.).

In the central Mediterranean the main fisheries targeting red shrimps are located along the Italian Ionian Sea, where fishing occurs from coastal

26 F. SARDÀ et al.

waters to 700-750 m. Fish, crustaceans and cephalopods make up about 70, 20 and 10% of the mean catch respectively. Commercial fish and cephalopods are mostly caught on the continental shelf, while crustaceans with a high market value are mainly fished on the slope (between 200 and 400 m mostly Parapenaeus longirostris; between 400 and 700 m A. antennatus and A. foliacea). N. norvegicus is mostly caught on the continental shelf along the Apulian coasts and on the slope along the Calabria (Tursi et al., 1994, 1998). In general, high- er activity rates in the red shrimp fishing fleet occur during spring and summer for the following reasons: a) better weather conditions which also encourage small vessels to fish far from the coast on red shrimp fishing bottoms; b) increased commercial demand and average price as a result of the increase in tourists along the coast; and c) the longer duration of the daylight, making it possible to explore more areas if the target species is scarce.

During an EU study project (Sardà, 2001) con- ducted in the Gallipoli fishery, it was shown that the fishing on the red shrimps was carried out by 45.8% of the trawlers. On average, the contribution of red shrimps made up 58.6% in weight and 66.15% in economic value of the total catch (Car- lucci et al., in press).

The exploitation of both species progressively decreased until the collapse of the stocks in the late 1970s. While a recovery of A. antennatus stock was shown in 1985, which led to a restart of the fishing activity (Orsi Relini and Relini, 1988), the presence of A. foliacea in the area is currently extremely scarce and insignificant in commercial terms (Fiorentino et al., 1998). Overfishing together with environmental decay, hydrology, failure of recruitment and parasitic attack of stressed stock were considered as the possi- ble causes of the stock collapse (Orsi Relini and Reli- ni, 1985; Relini and Orsi Relini, 1987).

Nowadays, thousand of tons of these species are landed along the Mediterranean coasts of the west- ern and central basin (Relini et al., 1999; Demestre and Martín, 1993; Tudela et al., 2003; Carbonell et al., 1999; García-Rodríguez, 2003). Red shrimp fisheries are often distinct even if a degree of over- lapping exists: the main A. foliacea fisheries are located in the Strait of Sicily and in Southern Sar- dinia, whereas A. antennatus is mostly caught in the western Mediterranean and in the Ionian Sea (Fig. 4), west-east and north-south gradients (Bian- chini and Ragonese, 1994; Cau et al., 2002; Sardà et al., 2001).

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