Sicilian dolphinfish ( Coryphaena hippurus ) fishery *

At the end of summer and during the autumn (August-December), along the eastern and western coasts of Sicily, dolphinfish juveniles are caught by a large number of vessels using surrounding-nets to capture fish under the Fish Attracting Devices (FADs) typical of the Mediterranean. They are called “cannizzi”, or floating drifting objects (Bono et al., 1998; Morales Nin et al., 1995; Potoschi and Sturiale, 1996). In Malta, in Tunisia and in the Balearic islands this activity is practised in the same period and with similar procedures and equipment (Galea, 1961; Lozano Cabo, 1961; Massutí and Morales Nin, 1991; Zaouali, 1997). There is no documented information for other Mediterranean areas. The adult dolphinfish (age 1+) is also by-catch in albacore and swordfish fisheries (De Metrio et al., 1997). The aim of this work is to contribute to the knowledge of the fleet, the equipment and the fishing techniques, and also to estimate the fishing yields in the 1996 fishing season in Sicily and its islands.


INTRODUCTION
At the end of summer and during the autumn (August-December), along the eastern and western coasts of Sicily, dolphinfish juveniles are caught by a large number of vessels using surrounding-nets to capture fish under the Fish Attracting Devices (FADs) typical of the Mediterranean.They are called "cannizzi", or floating drifting objects (Bono et al., 1998;Morales Nin et al., 1995;Potoschi and Sturiale, 1996).In Malta, in Tunisia and in the Balearic islands this activity is practised in the same period and with similar procedures and equipment (Galea, 1961;Lozano Cabo, 1961;Massutí and Morales Nin, 1991;Zaouali, 1997).There is no documented information for other Mediterranean areas.The adult dolphinfish (age 1+) is also by-catch in albacore and swordfish fisheries (De Metrio et al., 1997).The aim of this work is to contribute to the knowledge of the fleet, the equipment and the fishing techniques, and also to estimate the fishing yields in the 1996 fishing season in Sicily and its islands.

MATERIAL AND METHODS
At the beginning of the 1996 fishing season, a frame survey was carried out through a census in all ports of Sicily, Egadi Islands, Pelagie Islands and Eolie Islands.Thus, all the fishing boats which fish dolphinfish by means of "cannizzi" and purse-seine were identified.All captains of the boats were interviewed for information on the structural features of the boats, nets and FADs; in addition, information was obtained on the number and the geographical position of all the FADs placed in 1996.On the basis of this information the study area, consisting of the fishing areas of the aforementioned boats, was divided into the following strata (Fig. 1 In each of these strata at least one sample port (in bold type) was randomly selected, with the probability of selection proportional to the number of fishing boats of the port (Cochran, 1977;Bazigos et al., 1984;Andreoli et al., 1995).In some sample ports of strata A, B, C, E and F the catch-effort data were acquired on a time and space sampling basis by interviewing fishermen at landing.In practice interviews were conducted from the start to the end of the fishing season three times a week (Monday, Wednesday and Friday) on landing, with as many fishermen as possible.In stratum D (Lampedusa and Linosa) and in the sample ports of S. Agata Militello (stratum E) and Siracusa (stratum F) a time and space census system was adopted which enabled the catches of all the boats on all fishing days to be recorded.

Fleet characteristics
Table 1 shows the number of boats per port and their characteristics for west (Strata: A,B,C,D) and east (Strata: E,F) Sicily.A substantial difference can be seen between the two fleets.This difference is mainly in the overall length and the gross tonnage.The boats of west Sicily have an average overall length of 9.85 m and a gross tonnage of 5.76 t, while those of east Sicily have an average length of 11.41 m and an average gross tonnage of 10.42 t.The low average size of the boats of west Sicily is due to some small boats which fish near the coast.The fleet of east Sicily is represented by larger boats that only perform this type of fishing for a limited period of the year.In other periods they engage in fishing activities in which the length, tonnage and engine power have considerable importance, such as longline and drifting-net fishing for swordfish, and purse-seining for small pelagics.In west Sicily the smaller fishing boats are engaged in fishing dolphinfish from September to December.During the other months they fish using "trammel-net", bottom long-lines or gill-nets and drift-gill-nets for small and medium-sized pelagics.The larger fishing boats are generally engaged from the end of fishing dolphinfish to March in fishing with hand lines or bottom long-lines, and from March to August in fishing sword fish with long-lines or small and mediumsized pelagics with purse-seine.

FADs and FAD deployment
Figure 1 shows the geographical arrangement of the "cannizzi" per port.Lines were drawn on the basis of knowledge of the coordinates of the two outer FADs, the total number of FADs and the average distance between the FADs.Each line represents the fishing area by single fisherman.
The FADs were very similar in shape for the two areas, and are similar to the "kannizzati" used in Malta (Fig. 2a).There are differences in the composition of the ballast and floats between different areas.The FADs are constructed with a number of empty plastic bottles tied together to form a single float, which is tied in turn to 2 palm branches.The anchor line exits from this floating unit.At about 1.5 metres in depth, 4 more palm branches are tied to this anchor line about 1.5 metres apart from each other.The entire FAD is anchored to an anchor typ-SICILIAN DOLPHINFISH FISHERY 441 ically made of one or more large stones or anchor blocks (Fig. 2c-d).
In the Pelagie Islands, the float consists of slabs of polystyrene placed in a jute sack.Four palm branches are tied to this float, and the entirety, with no submerged palms, is anchored as described above.Drifting FADs are occasionally used (Fig. 2e).
In Stratum A, the boats placed approximately 110 FADs in a corridor of sea extending between 0.  In Stratum E the fleet uses anchored FADs as the fishing method, except in Termini Imerese and Porticello where the boats use drifting FADs.In the case of these latter fleets, the area fished is much larger than the area occupied by anchored FADs.In the zone between Capo Milazzo and Capo d'Orlando, the area where the FADs are distributed is bounded in the north by the Eolie Islands, which also represent the limit of FAD positions for the Tyrrhenian area (Fig. 3a).In this Stratum, the total number of FADs used by each boat ranges between 40 and 80, and the anchorage depth is no more than 600 metres.In Stratum F, the Ionian coast of Sicily, the sea is deeper, so positioning FADs is more difficult because of the amount of wire needed to secure them to the sea bottom and the weight of the ballast required.There are 60 to 100 FADs per boat, and the distance between them is approximately 800 metres; the anchorage depth can be up to 1500 metres (Potoschi, 1995) (Fig. 3b).

Fishing net and fishery operations
The typical net used in Sicily, known as "lampugara" or "caponara", has a length of 180 m, a height of 45 m, one float every 0.14 m and 900 weights weighing 90 kg in all (Fig. 4).Among vessels the dimensions of the net, though not corresponding proportionally to the dimensions of the vessel, increase as gross tonnage increases.The fishing operation started in August in stratum F and in September in other areas.

Catches
During the 1996 fishing season, the catch data of dolphinfish were acquired per month and stratum in the ports (Table 2).The values included in the table show that out of a total of 377,432 tons caught in Sicily 28.44% was caught in Stratum E,38.14% in Stratum F,1.36% in Stratum A,15.76% in Stratum B,5.68% in Stratum C and 10.61% in Stratum D. The latter value increased due to the catches made by boats of Termini Imerese and Porticello, which fish by sighting the shoals which gather under the drifting floating devices.This increment is estimated to be 22,291 tons, equal to 5.9% of the catches made using "cannizzi".The monthly distribution of the catches gave the highest value in October, where the 158,018 tons represent 41.86% of the total catches for the 1996 fishing season.

CONCLUSIONS
In the Sicilian seas the dolphinfish has been fished for many years, but the fishing areas were limited and the fleet engaged in this activity was small.In recent years there has been an increase in the boats with a consequent expansion in the areas  for positioning the "FADs", which from the southern Ionian sea has extended to the northern part, the southern Tyrrhenian and west Sicily.
The catch systems used have not undergone substantial technological changes compared to the equipment of the past.
Over recent years the conviction has prevailed among fishermen that by increasing the decoy factor (number of "cannizzi") leads to a proportionally increase in catches.This may be considered when historical series of catch and effort are available, but at present, referring to the catches of more recent fishing seasons (Potoschi, 1996), a seasonal variable emerges which is linked without doubt to environmental factors related to ethological and biological aspects of the species, whose presence in Mediterranean waters shows scheduled periods of disappearance.
5 km and 11.0 km from the coast.The FADs are spaced 300 m apart and are examined periodically, weather permitting.In Stratum B each boat placed about 50 FADs.The area where the FADs from San Vito lo Capo fleet are deployed extends through an arc of 442 A. POTOSCHI et al.

TABLE 1 .
-Structure of the dolphinfish fishing fleet by port and by sample stratum on the west and east of Sicily for 1996.

TABLE 2 .
-Catches (kg) of dolphinfish per month and stratum during the 1996 fishing season.