Shark Depredation and Unwanted Bycatch in Pelagic Longline

Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries
A4.6. Interview Results
None of the interviewed fishermen are concerned with shark damage
to their gear. They estimate the damage caused by the sharks in a
typical set is close to zero. They reported that, at the moment, a
high amount of shark interactions simply does not occur. When it
occurs, the part of the gear that is most often lost to sharks is the
end of the branch line with hook and bait. A few branch lines (0 to
10) are lost on a typical set owing to sharks, so fishermen spend a
very little time and money replacing gear. Usually none, sometimes
only one or two target fishes per set are damaged or lost to sharks.
Fishermen say they can recognize shark damage versus other
fish, cetacean, or squid damage according to bite characteristics.
Almost every time they find a cut branch line, they say that is a
consequence of a shark catch. Shark species interacting with longline
fishing gear are mostly blue shark (Prionace glauca, 0-2 catches
per fishing trip), while porbeagle (Lamna nasus), shortfin mako
(Isurus oxyrichus) and smooth-hounds (Mustelus sp.) are rare.
In their opinion the first most frequently by-caught shark species
is the blue shark (Prionace glauca), the second is the thresher
shark (Alopias vulpinus), the third is the porbeagle (Lamna nasus).
Other occasionally caught species are the shortfin mako (Isurus
oxyrichus), the hammerheads (Sphyrna sp.) and the smooth-hounds
(Mustelus sp.). Most specimens are alive when hauled to the boat.
All mentioned species are marketable, but meat is sold at a low price
(2-5 €/kg). The thresher shark and the porbeagle are easily sold, the
blue shark has a low value (and almost all fishermen discard it), the
hammerheads in some cases are discarded because of the strong
smell. Fishermen discard not marketable sharks, usually by cutting
the branch line. The dehooker is largely unknown but, even when
this gear is shown, they say it is more simple and safer to cut the
branchline. When a shark is marketable, instead, it is hauled, killed
by beating and eviscerated. Entrails are discarded and thrown into
the water.
Finning has never occurred, and the meat is the only part of
shark to be sold. Even the long tail of the thresher shark (Alopias
vulpinus), that is usually cut for convenience, is discarded. All
interviewed fishermen do not know about shark regulations
(e.g. Council Regulation (EC) 1185/2003 forbidding finning)
and about protected shark species (e.g. basking shark Cetorhinus
maximus, CITES Appendix II). Anyway, catching sharks is not a
profitable business for fishermen at the moment (as well as in the
past). When asked, they say they would like to avoid shark capture
without lowering the catch of target species. On the other hand,
Italian fishermen are very quick in catching opportunities. If there
were substantial shark populations in the Italian waters and a local
market for shark fins, probably they would fish for sharks. By now,
the revenue from sharks is so low that it does not exceed the cost of
catching them. In fishermen’s opinion, no regulation changes could
affect this trend.
All interviewed fishermen do not use shark catch and depredation
avoidance methods, and did not try such methods in the past. When
they have a higher shark by-catch rate, they do not change the way they
fish (e.g. changing position, time, or bait). Some of them (4) said that
30 years ago they used branch line with a more strong end part (near
the hook), in order to reduce the cutting by the shark and capture it.
This type of fishing was never done for selling the meat or other parts
of a shark, but only to avoid loosing the branch line. Fishermen said
that they would kill every shark caught to reduce shark abundance,
which they believed would increase the swordfish catch rate.
Regarding opinions on the possible efficacy of avoidance methods,
some fishermen think it is possible to avoid peak areas and times of
shark abundance, and some think it is possible to reduce the detection
of baited hooks by refraining from chumming during the set and
not discarding offal and spent bait during the haul. In any case, they
have never tried these methods, and no one has ever chummed while
fishing. Some fishermen point out that the attractiveness of baited
hooks to sharks can be reduced using mackerel instead of squid bait.
In fishermen’s opinion, the most important factor that affects shark
catch is the hooks depth, followed by topographic and oceanographic
features. Interviewed fishermen are not inclined to use dehookers
to release sharks, some actually usually do not haul sharks (even
marketable ones) to avoid the risk of handling.
Captains and crew are little interested in reducing shark capture and
depredation. They have a very pragmatic attitude towards sharks,
with no consciousness of their ecological role. They know sharks are
not economically profitable, and they are persuaded that sharks are
now rare in the Italian waters (many fishermen compare actual very
low shark by-catch rates with very high rates dating back to more
than a decade ago). On the other hand, sharks cause little damage
to fishing gear and are dangerous to handle, so fishermen would like
to avoid them, if avoidance methods do not lower the catch rate of
target species.
A4.7. Shark Trade
As Vannuccini (1999) reported to FAO, Italian shark export has ever
been of little importance; for example in 2004 recorded values were
199 t and 469,000 $ (FAO, 2006). No data on the fishing gear used to
catch these sharks is available.
On the other hand Italy is one of the leading world importers of
sharks (Table A4.21). In 1998 the major supplier to Italy was Spain,
followed by Netherlands, United Kingdom, South Africa and France
(Vannuccini, 1999).
Porbeagle (Lamna nasus), smooth-hounds (Mustelus spp.), catsharks
(Scyliorhinus spp.) and piked dogfish (Squalus acanthias) are shown
in the list of the most imported species (Vannuccini, 1999).
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