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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USA Hawaii-based <strong>Pelagic</strong> Longl<strong>in</strong>e Swordfish <strong>and</strong> Tuna Fisheries<br />
A8.5. Economic, Social, <strong>and</strong> Ecological Effects,<br />
Includ<strong>in</strong>g Effects on Fish<strong>in</strong>g Practices, from<br />
Regulations Govern<strong>in</strong>g <strong>Shark</strong> Interactions<br />
Of the twelve fishermen <strong>in</strong>terviewed, n<strong>in</strong>e were longl<strong>in</strong><strong>in</strong>g based from<br />
Hawaii, one was longl<strong>in</strong><strong>in</strong>g based from California, <strong>and</strong> two were not<br />
longl<strong>in</strong><strong>in</strong>g <strong>in</strong> the U.S. prior to when the rules on shark f<strong>in</strong>n<strong>in</strong>g came<br />
<strong>in</strong>to effect. Eight of the ten fishermen who were fish<strong>in</strong>g <strong>in</strong> the U.S.<br />
before the shark f<strong>in</strong>n<strong>in</strong>g regulations came <strong>in</strong>to effect used to f<strong>in</strong> sharks,<br />
while two stated that they did not f<strong>in</strong> sharks when it was legal. The eight<br />
fishers that used to f<strong>in</strong> sharks had received a total of between $400 -<br />
$3000 per trip from the sale of shark f<strong>in</strong>s (mean of $1,620 per trip, or<br />
about $8,100 per crew per year, assum<strong>in</strong>g three crew per vessel <strong>and</strong><br />
15 trips per year). Crew received the revenue from the sale of f<strong>in</strong>s.<br />
This is generally consistent with f<strong>in</strong>d<strong>in</strong>gs of McCoy <strong>and</strong> Ishihara (1999)<br />
who report that, prior to the adoption of regulations on shark f<strong>in</strong>n<strong>in</strong>g,<br />
<strong>in</strong>come from shark f<strong>in</strong>s was reta<strong>in</strong>ed by the crew except for some<br />
vessels where owners, mostly on owner-operated vessels, reta<strong>in</strong>ed a<br />
share of the revenue from shark f<strong>in</strong>s. Hamilton (1996) reports that<br />
average annual wages for Hawaii longl<strong>in</strong>e crew was $22,000 based on<br />
data from 1993-1995. McCoy <strong>and</strong> Ishihara (1999) estimate that <strong>in</strong> 1998<br />
(prior to the adoption of regulations on shark f<strong>in</strong>n<strong>in</strong>g) crew earned<br />
an average annual <strong>in</strong>come from shark f<strong>in</strong> sales of between $2,375 to<br />
$2,850, 10-11% of their estimated annual wage. On some bad trips,<br />
a crew’s revenue from shark f<strong>in</strong>s could exceed their share from the<br />
sale of the catch. In 1998 an estimated 38 t of dried shark f<strong>in</strong>s with an<br />
ex-vessel value of about $1 million was produced, of which about 95%<br />
came from blue sharks (McCoy <strong>and</strong> Ishihara, 1999). In 1998, logbook<br />
records show that of 97,080 sharks caught by the Hawaii longl<strong>in</strong>e<br />
fleet, 58,444 sharks were f<strong>in</strong>ned (53,822 blue sharks, 579 mako, 1,357<br />
thresher, <strong>and</strong> 2,686 other) (McCoy <strong>and</strong> Ishihara, 1999).<br />
Most (66%) of the <strong>in</strong>terviewed fishermen report occasionally reta<strong>in</strong><strong>in</strong>g<br />
one mako shark every two or three trips, if it is caught <strong>in</strong> the last<br />
2-3 sets of the trip <strong>and</strong> space rema<strong>in</strong>s <strong>in</strong> the hold, <strong>and</strong> that they less<br />
frequently reta<strong>in</strong> a thresher shark. Two of the twelve fishermen report<br />
that they now discard the f<strong>in</strong>s of reta<strong>in</strong>ed sharks because the vessel<br />
owner or capta<strong>in</strong> does not want to risk violat<strong>in</strong>g the shark regulations<br />
or raise negative public perceptions. For vessels that do reta<strong>in</strong> f<strong>in</strong>s,<br />
crew still receive the revenue from the sale of the f<strong>in</strong>s, but this amounts<br />
only to about $50 from the sale of one set of mako or thresher f<strong>in</strong>s<br />
every one to two trips. Revenue from shark meat is divided by the<br />
vessel the same as any other l<strong>and</strong>ed fish. One capta<strong>in</strong> reports that his<br />
crew occasionally cleans <strong>and</strong> sells a mako jaw for about $25 a jaw.<br />
S<strong>in</strong>ce the restrictions on f<strong>in</strong>n<strong>in</strong>g came <strong>in</strong>to effect, the revenue from<br />
catch<strong>in</strong>g sharks is exceeded by the cost from shark depredation <strong>and</strong><br />
loss <strong>and</strong> damage to gear.<br />
Only one fisherman reports chang<strong>in</strong>g his fish<strong>in</strong>g methods as a result of<br />
the adoption of shark f<strong>in</strong>n<strong>in</strong>g restrictions; the capta<strong>in</strong> of this longl<strong>in</strong>e<br />
tuna vessel (F/V Garden Sun) now sets his ma<strong>in</strong> l<strong>in</strong>e shooter at a<br />
faster speed to make the ma<strong>in</strong> l<strong>in</strong>e relatively more slack to <strong>in</strong>crease<br />
its sett<strong>in</strong>g depth, to target higher quality tuna, but also to reduce the<br />
shark capture rate. All others report not hav<strong>in</strong>g made any changes to<br />
their fish<strong>in</strong>g methods <strong>and</strong> gear as a result of the shark f<strong>in</strong>n<strong>in</strong>g rule.<br />
A8.6. Practices to Deal with Caught <strong>Shark</strong>s <strong>and</strong><br />
Costs from <strong>Shark</strong> <strong>Depredation</strong> <strong>and</strong> Gear Damage<br />
Almost all Hawaii longl<strong>in</strong>e tuna vessels use ca. 45 cm-long wire<br />
traces at the end of branch l<strong>in</strong>es, located between the baited hook <strong>and</strong><br />
a weighted swivel, while swordfish vessels do not use a wire trace. As<br />
a result, sharks that bite baited hooks <strong>in</strong> tuna gear tend to be reta<strong>in</strong>ed<br />
on the l<strong>in</strong>e, while about a quarter of sharks that bite baited hooks <strong>in</strong><br />
swordfish gear bite through the monofilament l<strong>in</strong>e <strong>and</strong> are not reta<strong>in</strong>ed<br />
on the l<strong>in</strong>e to be hauled to the vessel. Longl<strong>in</strong>e tuna vessels catch an<br />
average of 9.5 sharks on a typical set. Longl<strong>in</strong>e swordfish vessels catch<br />
an average of 25 sharks on a typical set.<br />
The potential exists to <strong>in</strong>crease post release survival prospects <strong>and</strong><br />
reduce fish<strong>in</strong>g mortality of caught <strong>and</strong> discarded sharks through<br />
improved h<strong>and</strong>l<strong>in</strong>g <strong>and</strong> release practices by crew. For about 66% of<br />
caught sharks, crew cut branch l<strong>in</strong>es after br<strong>in</strong>g<strong>in</strong>g the shark as close to<br />
the vessel hull as possible. For about 34% of caught sharks, when crew<br />
are not too busy process<strong>in</strong>g commercially valuable caught fish, they<br />
will br<strong>in</strong>g smaller sharks of species that are relatively easier to h<strong>and</strong>le<br />
or that are dead when hauled to the vessel <strong>and</strong> are small enough to<br />
lift up onto the rail on the bulwark <strong>and</strong> remove the hook with a small<br />
filet knife (Fig. A8.2). Crew report be<strong>in</strong>g able to occasionally yank<br />
the hook out of a caught shark that is loosely-hooked. When the<br />
crew cut the branch l<strong>in</strong>e to discard a shark, they will usually lose the<br />
term<strong>in</strong>al tackle, <strong>in</strong>clud<strong>in</strong>g the hook, wire leader, swivel, <strong>and</strong> a bit of<br />
monofilament l<strong>in</strong>e for tuna gear, <strong>and</strong> the hook, monofilament l<strong>in</strong>e, <strong>and</strong><br />
sometimes a lightstick <strong>and</strong> swivel for swordfish gear. Some crew on<br />
tuna vessels report that they occasionally are able to br<strong>in</strong>g the caught<br />
shark close enough to the vessel hull to cut the wire leader to discard<br />
a shark, thus reta<strong>in</strong><strong>in</strong>g the swivel <strong>and</strong> part of the wire. If there are fish<br />
on deck that need to be processed <strong>and</strong> preserved, crew may decide not<br />
to spend time <strong>and</strong> effort h<strong>and</strong>l<strong>in</strong>g sharks to retrieve term<strong>in</strong>al tackle<br />
<strong>and</strong> cut branch l<strong>in</strong>es conta<strong>in</strong><strong>in</strong>g sharks or dropp<strong>in</strong>g the entire branch<br />
l<strong>in</strong>e conta<strong>in</strong><strong>in</strong>g the caught shark. Two fishers report that, when they<br />
are busy process<strong>in</strong>g commercially valuable species, they will place a<br />
tarred rope with a knot at the end off the stern <strong>and</strong> will clip branch<br />
l<strong>in</strong>es conta<strong>in</strong><strong>in</strong>g sharks onto this rope so they can remove the sharks<br />
from the gear after they have completed the haul <strong>and</strong> processed the<br />
catch. At the end of the haul, about 75% of the sharks that are put on<br />
the ‘shark l<strong>in</strong>e’ have fallen off the hooks, some of the l<strong>in</strong>es break (<strong>and</strong><br />
the weighted swivels hit the stern of the vessel – this vessel has a high<br />
bulwark so these fly<strong>in</strong>g weights do not pose a risk to the crew), while<br />
the sharks rema<strong>in</strong><strong>in</strong>g on the l<strong>in</strong>e at the end of the haul are usually dead.<br />
One capta<strong>in</strong> reports kill<strong>in</strong>g all caught sharks <strong>in</strong> an effort to m<strong>in</strong>imize<br />
future shark depredation, which is a practice also reported by McCoy<br />
<strong>and</strong> Ishihara (1999), however observer data show that a very small<br />
proportion of caught sharks that are alive when hauled to the vessel are<br />
killed before discard<strong>in</strong>g (Tables A8.7 <strong>and</strong> A8.8). Several respondents<br />
reported catch<strong>in</strong>g the same shark as many as ten times <strong>in</strong> a s<strong>in</strong>gle haul.<br />
McCoy <strong>and</strong> Ishihara (1999) report that before restrictions on f<strong>in</strong>n<strong>in</strong>g<br />
were <strong>in</strong>stituted, some Hawaii longl<strong>in</strong>e fishers had used a 220-volt<br />
electrical l<strong>in</strong>e rigged to a gaff to stun sharks before l<strong>and</strong><strong>in</strong>g. None of<br />
the <strong>in</strong>terviewed fishers report us<strong>in</strong>g a dehooker device to try to remove<br />
a hook from a caught shark because they believe this would be more<br />
dangerous or time consum<strong>in</strong>g than their current practice, <strong>and</strong> that it<br />
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