Shark Depredation and Unwanted Bycatch in Pelagic Longline

Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries
A5.5.2. Kinkai fleet handling and disposition
The kinkai fleet displayed the widest range of targeting strategies,
including different gear and fishing ground variations by season, and
thus showed the greatest diversity in shark handling and disposition.
Despite this variation, fishermen could generally be divided into
two groups with regard to their interactions with sharks: a) bycatch
fisheries outside of Kesennuma, which fin sharks and discard the
carcass; b) bycatch or shark targeting fisheries in Kesennuma which
utilize both fins and meat.
The one fishermen from a bycatch fishery located outside of
Kesennuma who was interviewed usually fins sharks and discards
the carcass. He reported using both wire and monofilament leaders,
sometimes in the same set or even the same basket. The lack of a local
market was cited as the reason for not utilizing shark meat. Sharks
are handled by gaffing and then cutting off the head and fins. The
only sharks which are sometimes retained whole are the thresher
sharks which were claimed to have lower urea content than other
sharks. Other sharks including shortfin mako sharks are reportedly
finned and discarded. Extremely large sharks may be cut off the line
to avoid endangering the crew. This fishermen explained that he
provides an incentive to his crew, which are mostly Filipino, to fin
sharks by offering each of them a bonus of 5,000-10,000 yen (roughly
50 -100 USD) per cruise if they fin hauled sharks.
Interviews were also conducted with representatives of fisheries
utilizing the whole shark mainly based in or around Kesennuma
(n=13), where there is a stable market for shark products. These
vessels are usually targeting billfish with shallow sets 6 or tuna, such
as bigeye, with deep sets, but some vessels also explicitly targeted
sharks during some times of the year. Shallow set operations for
billfish are believed to catch more sharks, and especially when
billfish numbers are expected to be low, wire leaders are often used
to maximize retention of hooked sharks. One respondent claimed
that catching 10 blue sharks would be equivalent in value to catching
1 billfish. The price for blue shark meat in Kesennuma at the time of
the interview (April 2006) was $1.70 to $2.10 US per kg. A variety of
practices were employed to handle the estimated 80-90% of sharks
which are still alive when brought to the boat. These included:
• Gaff the shark, pull the shark with the wire leader so that it is
pinned against a large object and using 3-4 crew to immobilize
it, cut the vertebrae 7 ;
• Hit the shark with a long handled wooden mallet to immobilize
it before cutting;
• Drag the shark by means of the leader into a clamping device bolted
to the deck (flat on one side, convex on the other, dimensions of
50 cm length, 44 cm width, 16.5 cm height with a 1.1m closing
handle pole (Fig. A5.8)); close the clamp and kill the shark with
a steel pike.
Fig. A5.8. Clamping device designed and used by one kinkai fisherman
based in Kesennuma for immobilizing sharks. (Photo courtesy of T. Miyamoto.)
When cutting the head, as much as possible of the vertebrae near the
dorsal surface is retained but the gills, located at the same anterior
distance from the snout on the ventral surface, are removed. This is
achieved by means of an S-shaped cut through the vertical axis of the
shark. After removing the head, the shark is gutted but the fins are
left intact. According to interviews with Kesennuma-based fishermen,
there is no shark that is too big to be landed and all sharks which
do not bite off the hook and escape will be brought on deck. A few
respondents said they would release small sharks if they are still alive
after hauling.
A5.5.3. Engan fleet handling and disposition
With some minor exceptions, shark handling and disposition
practices in the engan fleet were similar to those in the kinkai fleet.
Among the interview participants, several of the fishermen out of
Kii-Katsuura (n=4) used an electric “shocker” device to stun sharks
in the water before they are brought on deck. This device changes
handling practices but did not seem to influence overall shark
disposition (i.e. whether or not the carcass is retained). Another
major difference was found in engan fishermen in Kii-Katsuura:
while the market for shark products was deemed too small to warrant
shark carcass retention by the Kii-Katsuura based kinkai fisherman
(see above), the Kii-Katsuura engan fishermen usually retain shark
carcasses. 8 There is a small shark products factory in Kii-Katsuura which
processes shark meat, including blue and thresher shark meat, into
semi-dried filets (tareboshi), processes a small number of fins, and sells
the remaining fins to a dealer in Kobe for export to China (Fig. A5.9).
On the smallest of the engan vessels, captains fish alone, i.e. without
crew. Three of the four respondents in this category use nylon
monofilament leaders to target tuna and billfish. The other respondent
usually targets tuna with monofilament leaders but during the
summer months he targets sharks using wire for the last 1 m of the
branch line. 9 Due to crew limitations, these fishermen were forced to
6
One respondent mentioned that the Kesennuma style of fishing for billfish is similar to that used in the Hawaii longline fishery.
7
While some respondents claimed this could be achieved by one crew member “riding the shark” while the others assisted, this was considered too dangerous by other
respondents due to the possibility of rolling
8
Note that the large shark products market in Kesennuma encourages both kinkai and engan fishermen there to retain shark carcasses but the small size of the market in Kii-
Katsuura will support only the engan shark catches.
9
This fishermen claimed he was one of only two fishermen targeting sharks out of Kii-Katsuura in the summer months. Because of the high prices paid for thresher ($250 US
per fish) and shortfin mako ($50 US per fish) he is targeting these species but the majority of his catch (20-30 sharks per day) is blue shark. His catch of fins and meat is sold
to the small factory in Kii-Katsuura. Aside from this factory there are four other fin dealers in Kii-Katsuura with strong connections to the China market.
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