Shark Depredation and Unwanted Bycatch in Pelagic Longline

Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries
Table A4.5. Italian fishing fleet: catches of sharks in 2004 (IREPA, 2006).
Catch (t) Revenue (mln) Price /kg
Sharks 951 4.66 4.90
Total fish 201,230 814.42 4.05
Table A4.6. Italian fleet: shark catches, revenue and price, 2004
(IREPA, 2006).
Catches (t) Revenue (mln) Price /kg
Trawlers 308 1.73 5.64
Small
scale
517 2.58 4.98
Longliners 50 0.09 1.88
Total 951 4.66 4.90
Table A4.7. Small-scale and large-scale pelagic and demersal longline
Italian fleet: catches of sharks and target species, 2004 (IREPA, 2006).
Catch (t)
Revenue
(million)
Price/kg
Sharks 50 0.09 1.88
Swordfish – Xiphias gladius 3,884 46.98 12.10
Northern bluefin tuna – Thunnus
thynnus
319 2.28 7.13
Albacore – Thunnus alalunga 1,115 4.32 3.88
Total fish 8,782 79.17 9.02
There is no Italian longline fishery that targets sharks. Traditional
fishing activities with demersal longline targeting chondrichthyans,
such as bluntnose sixgill shark (Hexanchus griseus) fishing in the
Ionian Sea and kitefin shark (Dalatias licha) fishing in the Ligurian
Sea, have long been abandoned (Vacchi & Notarbartolo di Sciara,
2000). Shark finning does not occur on Italian vessels (Orsi Relini,
2000). In any case, Council Regulation (EC) 1185/2003 provides that
removing shark fins on board, retaining and sell them is prohibited.
Sharks are captured mainly by trawlers (32.4%) and small scale
fishing practices (54.4%), or as by-catch of longliners (5.3%) (Table
A4.6) (IREPA, 2006).
Official data and statistics on shark catches and by-catches suffer
from the same, already mentioned problem: no data are available for
drifting longline only, because drifting and set gears are included in
the same class (Table A4.7), which also includes small- and large-scale
fisheries.
Moreover, official trend data on shark catches are of limited utility
and difficult to interpret because many species of small and medium
sized sharks are generically recorded as “palombo” (Mustelus spp.)
(De Metrio et al., 1982b; Vacchi & Notarbartolo di Sciara, 2000) and
so reported to international bodies (Table A4.8).
According to Vannuccini (1999), the main shark species caught by
the Italian fleet as by-catch are blue sharks (Prionace glauca),thresher
(Alopias vulpinus) and porbeagle (Lamna nasus). Di Natale (1998)
enclosed a list of shark species reported in the by-catch of the Italian
longline large pelagic fishery: Alopias vulpinus, Alopias superciliosus,
Carcharhinus brevipinna, Carcharhinus limbatus, Carcharhinus
obscurus, Carcharhinus plumbeus, Prionace glaca, Cetorhynus maximus,
Heptranchias perlo, Hexanchus griseus, Carcharodon carcharias, Isurus
oxyrinchus, Lamna nasus, Eugomphodus taurus, Odontaspis ferox,
Sphyrna zygaena, Sphyrna mokarran, Sphyrna sp., Squalus acanthias,
Squalus blainvillei, Galeorhinus galeus, Mustelus mustelus. The same
author (Di Natale, 1998) also reported that some shark species, such as
Alopias ssp., Isurus oxyrhinchus, Lamna nasus, are usually marketed,
while other species are sometimes marketed (Prionace glauca,
Carcharhinus ssp., Carcharodon carcharias, Squalus ssp., Heptranchias
perlo, Hexanchus griseus, Mustelus ssp., Sphyrna ssp.). Guglielmi et al.
(2000) reported that Prionace glauca is marketed only by some fisheries
(mainly on Adriatic Sea coast), while other species (Isurus oxyrhinchus
and Lamna nasus) are valuable and usually marketed. De Metrio et
al. (1982a), in a paper related to blue shark dynamics of fishing in the
Salento area (North Ionian Sea), reported a trade of this species, with
more then 1,000 specimen totally landed in 1979-1980.
Quantitative data about drifting longline shark by-catch are available
from a few papers. We subdivide bibliographic material according
to the seas where the studies were carried on. Unfortunately, these
papers usually do not provide separate data for small-scale and largescale
longline fisheries.
A4.5. Mediterranean Sea
Megalofonou et al. (2005) conducted a study of incidental catches
and discards of pelagic sharks from the swordfish and tuna fisheries
in the Mediterranean Sea. Data were taken onboard and at fishing
ports from 1998 to 2000 (Table A4.9). Sharks comprise about 18% of
the total catch of the Italy Mediterranean Sea large pelagic longline
fishery. Blue shark (Prionace glauca) was the main by-catch species in
all gears and areas examined. The next most abundant species were
shortfin mako (Isurus oxyrinchus), thresher shark (Alopias vulpinus),
and tope shark (Galeorhinus galeus) (Megalofonou et al., 2005).
Table A4.10 shows data related to Italian waters recorded onboard
during a study by Megalofonou et al. (2005), where the average shark
combined species CPUE of the four fishing areas was 0.744 sharks
combined species per 1000 hooks.
Guglielmi et al. (2000) present data from onboard observations
during fishing seasons 1998-1999. Sharks were caught by swordfish,
albacore and Northern bluefin tuna longline vessels in the Central
Mediterranean Sea (Table A4.11).
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