SCRS/2014/111 Collect. Vol. Sci. Pap. ICCAT, 71(5): 2073-2078 (2015)

SWORDFISH (XIPHIAS GLADIUS L.) FISHERIES USING MESOPELAGIC

LONGLINE IN THE MEDITERRANEAN SEA BY ITALIAN FISHING FLEET

Francesco Bertolino1, Claudia Camolese1, Marco Dell’Aquila1,

Adriano Mariani1, Massimiliano Valastro1

SUMMARY

The use of the traditional and mesopelagic longline in Italy in 2012 was investigated to evalu-

ate 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 palan-

griers 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 243 – 00184 Roma, Italy (bertolinof@gmail.com; c.camolese@unumar.it; m.dellaquila@unimar.it;

mariani.a@unimar.it; bubuval@hotmail.com).

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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).

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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. 2011. 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): 1405-1470.

Di Natale, A., Mangano, A., Navarra, E., Schimmenti, G., Valastro, M. 1995. Swordfish (Xiphias gladius)

longline fishing in the Tyrrhenian Sea and in the Strait of Sicily: 1992 Report. Col. Vol. Sci. Pap. ICCAT

44(1): 249-254.

Di Natale, A. and Mangano, A. 2008. CPUE series (1985-2006) by gear type in the Tyrrhenian Sea and in the

Strait of Sicily. Col. Vol. Sci. Pap. ICCAT, 62(4): 1128-1141.

Tserpes G., Peristeraki P., Di Natale A., Mangano A., 2008. Standardization of swordfish (Xiphias gladius) catch

rates from the Greek and Italian Mediterranean longline fisheries. Col. Vol. Sci. Pap. ICCAT, 62(4): 1074-

1080.

Orsi Relini, L., Palandri, G., Garibaldi, F., Cima, C., Lanteri, L., Relini, M., 2008. 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): 1097-1106.

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Table 1. Vessels using swordfish longline observed in different Italian ports.

Administrative

region

Number of

vessels

Surface longline

only

Mesopelagic

longline only

Surface and

mesopelagic longline

N % N % N %

Sicily 167 17 10,2 150 89,8

Sardinia 59 5 8,5 54 91,5

Liguria 29 29 100

Tuscany 18 18 100

Lazio 16 16 100

Calabria 32 5 15,6 27 84,4

Puglia 31 5 16,1 26 83,9

Table 2. Characteristics of the two types of longline.

Gear characteristics Longline

mesopelagic traditional

Operating depth (m): min - max 50 – 800 15 – 60

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 2 - 3 1

Time at sea (h): min. - max. 24 - 48 5 - 10

Operating average bathimetry (m) 250 50

Stabilizing mass yes no

Presents of attractive lights no yes

Table 3. Rate distribution of the catches.

LJFL (cm) % longline

mesopelagic traditional

80-85 0,2 4,3

85-90 1,2 9,6

90-95 3,7 10,4

95-100 7,6 11,5

100-105 6,1 13,1

105-110 5,4 9,9

110-115 11,2 9,6

115-120 10,4 10,4

120-125 9,6 8,3

125-130 8,6 4,0

130-135 7,3 3,7

135-140 7,2 2,1

140-145 4,1 1,6

145-150 4,1 0,5

150-155 4,5 0,5

155-160 1,5 0,0

160-165 1,7 0,0

165-170 1,1 0,0

170-175 1,1 0,0

175-180 0,9 0,3

180-185 0,5 0,0

185-190 0,7 0,3

190-195 0,3 0,0

195-200 0,4 0,0

200-205 0,2 0,0

205-210 0,1 0,0

210-215 0,1 0,0

220-225 0,1 0,0

230-235 0,1 0,0

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Figure 1. Italian geographic distribution of the fleet using swordfish drifting longline.

Figure 2. Swordfish longline fishing area monitorated.

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Figure 3. Size Frequency distribution of catches of two types of pelagic longlines (surface and midwater).

0

2

4

6

8

10

12

14

80-85

85-90

90-95

95-100

100-105

105-110

110-115

115-120

120-125

125-130

130-135

135-140

140-145

145-150

150-155

155-160

160-165

165-170

170-175

175-180

180-185

185-190

190-195

195-200

200-205

205-210

210-215

220-225

230-235

%

LJFL (cm)

mid-water traditional

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