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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Peru Artisanal Mahimahi And <strong>Shark</strong> Longl<strong>in</strong>e Fishery<br />
A6.13. Perceptions on Efficacy <strong>and</strong> Commercial<br />
Viability of Strategies to Reduce <strong>Shark</strong> Interactions<br />
A6.13.1. Avoid<strong>in</strong>g peak areas <strong>and</strong> times of shark abundance<br />
Almost two thirds (64%) of respondents believe that shark catch rates<br />
will be highest <strong>in</strong> certa<strong>in</strong> areas which are different from those of the<br />
target species. Half of respondents (50%) believe that it is possible to<br />
avoid peak areas <strong>and</strong> times of shark abundance. One third (33%) of<br />
respondents believe this is not possible because shark capture is more<br />
profitable <strong>and</strong> they would rather capture sharks if they encounter areas<br />
of high shark abundance. This was not the common view, however,<br />
because dur<strong>in</strong>g the summer mahi mahi are more abundant <strong>and</strong> easily<br />
available.<br />
A6.13.2. Reduc<strong>in</strong>g the detection of baited hooks by sharks,<br />
such as by refra<strong>in</strong><strong>in</strong>g from chumm<strong>in</strong>g dur<strong>in</strong>g the set <strong>and</strong><br />
not discard<strong>in</strong>g offal <strong>and</strong> spent bait dur<strong>in</strong>g the haul<br />
About half of respondents (48%) do not believe that refra<strong>in</strong><strong>in</strong>g from<br />
chumm<strong>in</strong>g dur<strong>in</strong>g the set <strong>and</strong> refra<strong>in</strong><strong>in</strong>g from discard<strong>in</strong>g offal<br />
<strong>and</strong> spent bait dur<strong>in</strong>g the haul will reduce shark depredation <strong>and</strong><br />
bycatch. Thirty-three percent of respondents believe it may help<br />
reduce <strong>in</strong>teractions with shark species. All vessels discard spent bait<br />
<strong>and</strong> offal dur<strong>in</strong>g the haul, <strong>and</strong> most respondents believe it would<br />
be impractical to reta<strong>in</strong> spent bait <strong>and</strong> offal to discard at the end of<br />
haul<strong>in</strong>g because of the lack of space on the vessels.<br />
A6.13.3. Limit<strong>in</strong>g shark access to baited hooks, such as<br />
alter<strong>in</strong>g fish<strong>in</strong>g practices to consider deployment depth of<br />
hooks <strong>and</strong> tim<strong>in</strong>g of the soak <strong>and</strong> haul to avoid problematic<br />
shark species<br />
Almost half (46%) of respondents believe that it is possible to reduce<br />
shark <strong>in</strong>teractions by sett<strong>in</strong>g baited hooks shallower or reduc<strong>in</strong>g<br />
soak<strong>in</strong>g time. Another 43% of respondents believe it is not possible<br />
because they still have shark <strong>in</strong>teractions when sett<strong>in</strong>g baited hooks<br />
shallower. Dur<strong>in</strong>g mahi mahi season, baited hooks are set as deep as<br />
6 fathoms whereas dur<strong>in</strong>g shark season hooks are set as deep as 11<br />
fathoms. None of the respondents mentioned sett<strong>in</strong>g baited hooks<br />
deeper because it would reduce their catch rate of target species.<br />
A6.13.4. Deterr<strong>in</strong>g sharks such as with chemical shark<br />
deterrents <strong>and</strong> electrical deterrents<br />
Only 17% of respondents believe that deterrents such as chemical<br />
compounds <strong>and</strong> electrical currents will be effective at reduc<strong>in</strong>g shark<br />
bycatch <strong>and</strong> depredation. Another 14% of respondents replied that<br />
they did not know of these deterrents or if they would be effective.<br />
Over half (62%) of respondents believe that us<strong>in</strong>g shark deterrents<br />
would not be feasible s<strong>in</strong>ce they want to capture them due to their<br />
high economical value. Respondents (17%) who replied that these<br />
deterrents may work mentioned that they would probably be too<br />
expensive to use. Some respondents (14%) replied that shark capture<br />
is not a problem for them, but, rather, an economic benefit.<br />
A6.13.5. Reduc<strong>in</strong>g the attractiveness of baited hooks to<br />
sharks, such as by us<strong>in</strong>g artificial baits, us<strong>in</strong>g or not us<strong>in</strong>g<br />
light sticks, or avoid<strong>in</strong>g a bait type known to result <strong>in</strong> high<br />
shark catch rates<br />
Over a quarter (29%) of respondents believe that avoid<strong>in</strong>g bait<br />
types known to result <strong>in</strong> high shark catch rates would reduce shark<br />
<strong>in</strong>teractions. About half (43%) of respondents replied that these<br />
strategies would not be effective s<strong>in</strong>ce shark <strong>in</strong>teractions occur even<br />
when not us<strong>in</strong>g bait types typically employed for shark capture. Of<br />
these, four respondents (10%) believe artificial bait would not be<br />
economically viable for mahi mahi capture s<strong>in</strong>ce bait type for this<br />
target species is captured fresh before the sett<strong>in</strong>g of the longl<strong>in</strong>e.<br />
Seven respondents (17%) replied that they do not know if these<br />
strategies would be effective. One respondent replied that he had<br />
used artificial bait but still had shark <strong>in</strong>teractions.<br />
A6.13.6. Reduc<strong>in</strong>g <strong>in</strong>jury to hooked sharks that you will<br />
discard<br />
Over a third (34%) of respondents discard live sharks below 40-60<br />
cm <strong>in</strong> length. Some respondents (7.1%) noted that small sharks that<br />
are to be discarded are easy to dehook. If the shark is hooked <strong>in</strong> the<br />
mouth this can be done manually without us<strong>in</strong>g any tools. If a shark<br />
is small but has swallowed the hook it will be killed <strong>and</strong> reta<strong>in</strong>ed.<br />
These respondents also believe that the use of dehookers could reduce<br />
<strong>in</strong>jury to hooked sharks that are to be discarded. One respondent<br />
replied that with tra<strong>in</strong><strong>in</strong>g he could use dehookers. Most respondents<br />
had not heard of or knew about dehookers. Two respondents replied<br />
that they used dehookers to recover hooks but that they did this once<br />
the sharks were on board <strong>and</strong> dead.<br />
A6.13.7. Reduc<strong>in</strong>g shark retention by avoid<strong>in</strong>g a specific size<br />
or type of hook, or by not us<strong>in</strong>g wire leaders on branch l<strong>in</strong>es<br />
Only one respondent (4.2%) replied that the size of the hook would<br />
affect the shark catch rate. Most respondents (69%) replied that shark<br />
retention is reduced by not us<strong>in</strong>g a wire leader on their branch l<strong>in</strong>es.<br />
Respondents use nylon monofilament only because they believe that<br />
us<strong>in</strong>g wire leaders would decrease their target species capture dur<strong>in</strong>g<br />
the summer. Wire leaders are used dur<strong>in</strong>g shark season to <strong>in</strong>crease<br />
shark capture.<br />
A6.13.8. Will the economic impact of sharks be reduced<br />
from us<strong>in</strong>g a wire leader on branch l<strong>in</strong>es<br />
Most respondents believe that the economic impact of sharks would<br />
be reduced by us<strong>in</strong>g a wire leader on branch l<strong>in</strong>es. Even though most<br />
of them f<strong>in</strong>d it economically beneficial to capture sharks, they will<br />
not switch to us<strong>in</strong>g a wire leader because it would reduce mahi mahi<br />
capture which is more abundant <strong>and</strong> easily available at summer time.<br />
A6.13.9. What is the most important factor that affects shark<br />
CPUE – alter<strong>in</strong>g fish<strong>in</strong>g position <strong>in</strong> relation to certa<strong>in</strong> water<br />
temperature, topographic features, or oceanographic features;<br />
chang<strong>in</strong>g the time of day or month of sett<strong>in</strong>g or haul<strong>in</strong>g; chang<strong>in</strong>g<br />
the depth of hooks, or a comb<strong>in</strong>ation of these factors?<br />
Thirty-eight percent of respondents believe that alter<strong>in</strong>g fish<strong>in</strong>g<br />
position <strong>in</strong> relation to certa<strong>in</strong> water temperatures alone will result <strong>in</strong><br />
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