Shark Depredation and Unwanted Bycatch in Pelagic Longline
Shark Depredation and Unwanted Bycatch in Pelagic Longline
Shark Depredation and Unwanted Bycatch in Pelagic Longline
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Japan <strong>Pelagic</strong> Longl<strong>in</strong>e Fisheries<br />
take a practical approach to shark h<strong>and</strong>l<strong>in</strong>g, therefore they will release<br />
sharks by cutt<strong>in</strong>g the l<strong>in</strong>e: a) when the shark is small <strong>and</strong> they wish<br />
to save time; b) when it is approach<strong>in</strong>g sunset <strong>and</strong> the haul is still<br />
not f<strong>in</strong>ished; or c) when fish<strong>in</strong>g for tuna <strong>and</strong> the shark is any species<br />
other than thresher (the seasonal fisherman). When sharks are hauled,<br />
the electrical “shocker” is used to send a 100-300V electrical current<br />
through a r<strong>in</strong>g with a small open<strong>in</strong>g <strong>in</strong> it (Fig. A5.10). This r<strong>in</strong>g is<br />
slid onto the branch l<strong>in</strong>e through the open<strong>in</strong>g <strong>and</strong> dropped from the<br />
gunwhale down the l<strong>in</strong>e <strong>in</strong>to the water until it contacts the shark. It<br />
is reportedly not dangerous to operate because the electric current is<br />
low <strong>and</strong> is effective only <strong>in</strong> water. Prior to its availability the crew used<br />
to have to try to immobilize the shark us<strong>in</strong>g the leader <strong>and</strong> fishermen<br />
compla<strong>in</strong>ed that this was both dangerous <strong>and</strong> time consum<strong>in</strong>g.<br />
Reta<strong>in</strong>ed sharks are headed <strong>and</strong> gutted, <strong>and</strong> f<strong>in</strong>s are reta<strong>in</strong>ed on the<br />
carcass for cutt<strong>in</strong>g <strong>in</strong> the port. Embryonic sharks are discarded <strong>and</strong><br />
sometimes swim away.<br />
Among the larger engan vessels, one targets sharks <strong>in</strong> the summer<br />
for the Kesennuma market, <strong>and</strong> several target tuna out of Kii-<br />
Katsuura or a variety of other ports <strong>in</strong> western Japan from Ok<strong>in</strong>awa<br />
to Kesennuma.<br />
Fig. A5.9. <strong>Shark</strong> meat <strong>and</strong> f<strong>in</strong> to be used for tareboshi <strong>and</strong> hukahire<br />
products at a small factory <strong>in</strong> Kii-Katsuura. (Photos courtesy of T. Miyamoto.)<br />
Fig. A5.10. The r<strong>in</strong>g <strong>and</strong> electrical cord of the “shocker” device used by<br />
engan fishermen based <strong>in</strong> Kii-Katsuura to immobilize sharks. (Photos courtesy<br />
of T. Miyamoto.)<br />
• The Kesennuma-based fisherman is target<strong>in</strong>g salmon sharks<br />
(Lamna ditropis) but often catches blue or shortf<strong>in</strong> mako sharks.<br />
He reports catch<strong>in</strong>g as many as 200-300 salmon sharks <strong>in</strong> a<br />
s<strong>in</strong>gle set. This species is apparently docile to h<strong>and</strong>le <strong>and</strong> it is<br />
thrown <strong>in</strong>to the hold, sprayed with cold water <strong>and</strong> settles down<br />
quickly. All process<strong>in</strong>g, <strong>in</strong>clud<strong>in</strong>g cutt<strong>in</strong>g of the valuable heart,<br />
is done <strong>in</strong> Kesennuma.<br />
• The more wide-rang<strong>in</strong>g fishermen (n= 2) had differ<strong>in</strong>g perspectives<br />
on the value of shark meat but both utilized shark f<strong>in</strong>s.<br />
t One fisherman realized that the dem<strong>and</strong> for shark meat was<br />
exp<strong>and</strong><strong>in</strong>g <strong>and</strong> had found markets for such meat <strong>in</strong> Kii-<br />
Katsuura, Choshi (Chiba Prefecture) <strong>and</strong> Shiogama (Miyagi<br />
Prefecture), as well as Kesennuma. For this reason, he reta<strong>in</strong>s<br />
any hooked shark <strong>in</strong> whole form (usually about 20 per set)<br />
by haul<strong>in</strong>g it onboard, us<strong>in</strong>g shears clamped on the shark’s<br />
head to immobilize it <strong>and</strong> head <strong>and</strong> gut it. F<strong>in</strong>s are left on the<br />
carcass. Profits from shark products are split evenly between<br />
company <strong>and</strong> crew but for other species profits are kept by the<br />
company. This respondent claimed that all large sharks would<br />
bite through the nylon monofilament leader <strong>and</strong> escape, but<br />
other sharks with the exception of threshers (due to danger<br />
from the long caudal f<strong>in</strong>) would be hauled.<br />
t Another wide-rang<strong>in</strong>g fisherman target<strong>in</strong>g tuna stuns all<br />
sharks with an electrical “shocker” before br<strong>in</strong>g<strong>in</strong>g them<br />
onboard, cuts the vertebrae as a safety precaution, f<strong>in</strong>s the<br />
shark, <strong>and</strong> discards the carcass. He stated that all sharks will<br />
be h<strong>and</strong>led <strong>in</strong> this manner regardless of size, though he noted<br />
most sharks he catches are <strong>in</strong> the range of 10-50 kg. Profits<br />
from shark f<strong>in</strong>s will be split evenly among the crew without<br />
the company tak<strong>in</strong>g a share unless the catch is very high<br />
(e.g. 70 kg of f<strong>in</strong>s worth 40,000-50,000 yen (350-450 USD)) <strong>in</strong><br />
which case the capta<strong>in</strong> will also take a share.<br />
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