SWORDFISH (XIPHIAS GLADIUS L.) FISHERIES USING MESOPELAGIC LONGLINE IN THE MEDITERRANEAN SEA BY ITALIAN FISHING FLEET

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1 SCRS/2014/111 Collect. Vol. Sci. Pap. ICCAT, 71(5): (2015) SWORDFISH (XIPHIAS GLADIUS L.) FISHERIES USING MESOPELAGIC LONGLINE IN THE MEDITERRANEAN SEA BY ITALIAN FISHING FLEET Francesco Bertolino 1, Claudia Camolese 1, Marco Dell Aquila 1, Adriano Mariani 1, Massimiliano Valastro 1 SUMMARY The use of the traditional and mesopelagic longline in Italy in 2012 was investigated to evaluate the effect of these gears in the swordfish fisheries. At least 800 longliners were estimated to have swordfish as the main target. A sample of 352 vessels was selected to collect information about the use of the gear and 26 vessels were selected to collect data about the sample size, (LJFL) and other relavant information about water depth of the fishing area, estimated depth of the longline during the operations, duration of set and hauls operation, total time of fishing, number of hooks. Nominal CPUE values were obtained from data collected. RÉSUMÉ On a étudié l'emploi de la palangre traditionnelle et mésopélagique en Italie en 2012 afin d'évaluer l'effet de ces engins dans les pêcheries d'espadon. On a estimé qu'environ 800 palangriers avaient pour cible principale l'espadon. Un échantillon de 352 navires a été sélectionné afin de recueillir des informations sur l'emploi de l'engin et 26 navires ont été sélectionnés pour recueillir des données sur la taille de l'échantillon (LJFL) et d'autres informations pertinentes sur la profondeur de l'eau dans la zone de pêche, la profondeur estimée de la palangre pendant les opérations, la durée des opérations et des remontées de l'engin, le temps de pêche total et le nombre d'hameçons. Les valeurs de la CPUE nominale ont été obtenues à partir des données rassemblées. RESUMEN Se investigó el uso del palangre tradicional y mesopelágico en Italia en 2012 para evaluar el efecto de estos artes en las pesquerías de pez espada. Se estimó que aproximadamente 800 palangreros se dirigen principalmente al pez espada. Se seleccionó una muestra de 352 buques para recopilar información acerca del uso del arte y 26 buques para recopilar datos acerca del tamaño de la muestra (LJFL) y otra información pertinente acerca de la profundidad del agua en la zona de pesca, la profundidad estimada del palangre durante las operaciones, las duración de las operaciones de calado y virada, el tiempo total de pesca y el número de anzuelos. Se obtuvieron valores de CPUE nominal a partir de los datos recopilados. KEYWORDS Xiphias gladius, Swordfish fisheries, Longline, Mediterranean, Tyrrhenian Sea, Size composition 1 Consorzio Unimar, Via Nazionale Roma, Italy (bertolinof@gmail.com; c.camolese@unumar.it; m.dellaquila@unimar.it; mariani.a@unimar.it; bubuval@hotmail.com). 2073

2 1. Introduction Swordfish is an important resource for the Italian fishery, usually practiced, in the past years, with driftnet and longlines, beside the harpoon fishery, traditionally carried out in the area of the Strait of Messina. Since the banning of the gillnet fishery ( spadara ) occurred in 2002 swordfish fishery is actually practiced only by pelagic longlines. Trying to regain profitability lost with the ban, some fishermen have gradually modified the traditional surface pelagic longline in a mesopelagic fishing gear, which has proven very efficient and it was gradually adopted by most of the Italian longline fleet. The development of such a system, while the one hand has probably reduced the fishing pressure on juveniles, on the other hand has increased the potential impact on adults, affecting the spawning stock. Many aspects of the fishing gear and the fisheries are not yet fully clear, especially in terms of their impact on the resource. Funded by the Italian Directorate for Fisheries of the Ministry of Agricultural and Forestry Policy, a project to examine the phenomenon was undertaken during 2012, comparing also distribution and methods of the two different fishing gears, the traditional surface longline and the mesopelagic longline, in order to allow the redaction of management measures. 2. Methods The project provided for three phases: a survey in the Italian ports in order to assess the presence of the traditional surface pelagic longline and the new mesopelagic gear, a one year long monitoring of catches in three representative sample ports, and a sampling campaign on board in the same three ports. A sample of 352 vessels was selected to collect information about the use of the gear, and a sub-sample of 26 vessels was selected to collect catch data. The size of the catches (lower jaw - fork length - LJFL) were collected during sampling, as well as technical data concerning fishing gears and other relevant information: water depth of the fishing area estimated depth of the longline during the operations set and hauls duration soaking time number of hooks. Nominal Commercial Catch per Unit Effort (CPUE) values in terms of Kg/1000 hooks were obtained from data collected. 3. Results and discussion The geographical distribution of the swordfish longline fleet is showed in Figure 1. In Italy, not less than 800 pelagic longliners are estimated to have swordfish as the main target. The vessels are mainly distributed in Tyrrhenian Sea, with the bulk of the fleet around Sicilian coasts (both Tyrrhenian and Ionian Sea), Straits of Messina, Sicilian channel and South Adriatic Sea. Regarding the three investigated areas, Figure 2 shows the fishing activities of the sampled vessels during one year (2012). Table 1 shows the use of the two gears in the selected boat sample. Even if the mesopelagic one is by far the most used the majority of vessels use both gears depending on the sea condition, season and fishing opportunity. In the Table 2 the main differences between the two fishing gears are reported. Surface longline is easier to manage and faster in the fishing activity (smaller size and shorter soaking time); it can be used by smaller boats and much closer to the coast (fishing in the surface layers) and produces its main effort only during night hours. Mesopelagic longline is often much longer, needs greater depths and distance from the coast. It fishes all the day long, exploring a huge water column. Usually more than one gear is set during the same fishing trip, therefore a greater fishing effort can be deployed. A total of 2070 individuals (LJFL between 81,8 and 235 cm, average length 121,73 cm) were sampled in three ports. In Figure 3 are reported the size frequency distribution data for catches of surface and mesopelagic gear. The mesopelagic gear catches on average bigger swordfish but also a wider size range, while surface longline catches are more limited to medium and small sizes (Table 3). 2074

3 CPUE values are 141,8 kg in the overall sampling, with partial values of 174,8 kg for mesopelagic and 78,5 kg for the surface longline. It is a very high yeld, if compared with other values about the same areas (Anon. 2011, Tserpes et al. 2008, Di Natale et al. 1995, Di Natale and Mangano 2008, Orsi Relini et al. 2008) proving the very good profitability in particular for the mesopelagic gear (values more than double of the other). 4. Conclusion Mesopelagic longline is replacing almost completely the surface gear, demonstrating a very good effectiveness on the whole range of sizes, including the big ones. Until today, even in a negative but fluctuating trend, there are not signs of dramatic decrease of the catches. Nevertheless the situation has to be taken under strict control, above all for spawning stock and juveniles. As for the spawning stock it is absolutely necessary not to increase the effort. As far as juveniles are concerned, the period of two-months closure of fishing activity (October- November) seems effective, while the problem of catches of juveniles and under-sized bycatch specimens would be completely solved by extending the prohibition during the same two months to all drifting pelagic longlines targeting other species such as albacore. References Anon Report of the 2010 ICCAT Mediterranean Swordfish Stock Assessment Meeting (Madrid, Spain June 28 to July 2, 2010). Col Vol. Sci. Pap. ICCAT 66(4): Di Natale, A., Mangano, A., Navarra, E., Schimmenti, G., Valastro, M Swordfish (Xiphias gladius) longline fishing in the Tyrrhenian Sea and in the Strait of Sicily: 1992 Report. Col. Vol. Sci. Pap. ICCAT 44(1): Di Natale, A. and Mangano, A CPUE series ( ) by gear type in the Tyrrhenian Sea and in the Strait of Sicily. Col. Vol. Sci. Pap. ICCAT, 62(4): Tserpes G., Peristeraki P., Di Natale A., Mangano A., Standardization of swordfish (Xiphias gladius) catch rates from the Greek and Italian Mediterranean longline fisheries. Col. Vol. Sci. Pap. ICCAT, 62(4): Orsi Relini, L., Palandri, G., Garibaldi, F., Cima, C., Lanteri, L., Relini, M., A time series of swordfish longline CPUE in the Northwestern Mediterranean: search for exploitation and/or climatic factors influencing fish abundance. Col. Vol. Sci. Pap. ICCAT 62(4):

4 Table 1. Vessels using swordfish longline observed in different Italian ports. Surface longline Mesopelagic Surface and Administrative Number of only longline only mesopelagic longline region vessels N % N % N % Sicily , ,8 Sardinia , ,5 Liguria Tuscany Lazio Calabria , ,4 Puglia , ,9 Table 2. Characteristics of the two types of longline. Longline Gear characteristics mesopelagic traditional Operating depth (m): min - max Gear lenght (Nm) Bigger boats: up to 30 Nm Small boats: 8-12 Nm Bigger boats: up to 30 Nm Hooks number per gear up to 1200 up to 1000 Number of gears per fishing trip Time at sea (h): min. - max Operating average bathimetry (m) Stabilizing mass yes no Presents of attractive lights no yes Table 3. Rate distribution of the catches. LJFL (cm) % longline mesopelagic traditional ,2 4, ,2 9, ,7 10, ,6 11, ,1 13, ,4 9, ,2 9, ,4 10, ,6 8, ,6 4, ,3 3, ,2 2, ,1 1, ,1 0, ,5 0, ,5 0, ,7 0, ,1 0, ,1 0, ,9 0, ,5 0, ,7 0, ,3 0, ,4 0, ,2 0, ,1 0, ,1 0, ,1 0, ,1 0,0 2076

5 Figure 1. Italian geographic distribution of the fleet using swordfish drifting longline. Figure 2. Swordfish longline fishing area monitorated. 2077

6 mid-water traditional % LJFL (cm) Figure 3. Size Frequency distribution of catches of two types of pelagic longlines (surface and midwater). 2078