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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<strong>Shark</strong> <strong>Depredation</strong> <strong>and</strong> <strong>Unwanted</strong> <strong>Bycatch</strong> <strong>in</strong> <strong>Pelagic</strong> Longl<strong>in</strong>e Fisheries<br />
Table 2.1. Generalized gear characteristics that may affect shark <strong>in</strong>teraction rates for n<strong>in</strong>e pelagic longl<strong>in</strong>e fisheries.<br />
<strong>Pelagic</strong> Longl<strong>in</strong>e Fishery<br />
Gear<br />
Characteristic<br />
Australia<br />
Tuna <strong>and</strong> Billfish<br />
Chile<br />
Artisanal Mahi Mahi<br />
<strong>and</strong> <strong>Shark</strong><br />
Chile<br />
Swordfish<br />
Spanish system I American-style<br />
Fiji<br />
Tuna<br />
Fish<strong>in</strong>g season All year <strong>Shark</strong>s year-round, mahi <strong>in</strong><br />
austral summer<br />
March - December<br />
All year<br />
Ma<strong>in</strong> l<strong>in</strong>e length 60 km 2.7 – 3.6 km 83 km 65 – 102 km 65-93 km<br />
Ma<strong>in</strong> l<strong>in</strong>e deployment Shooter Manual Manual Not known<br />
Trip duration 4 days 3-4 days for mahi target<strong>in</strong>g<br />
trips<br />
9-30 days<br />
Trips per year Not available Not known<br />
Sets per trip 3 7-25<br />
Hooks per set 950 100 - 350 1500 1200 - 2000 2300-2500<br />
Wire leader (trace)<br />
used?<br />
Typical m<strong>in</strong> depth of<br />
hooks<br />
Typical max depth of<br />
hooks<br />
No (prohibited)<br />
No when target<strong>in</strong>g mahi,<br />
yes when target<strong>in</strong>g sharks<br />
Yes or use<br />
poly-propylene<br />
33 m 9 m 58 m 50-180 m<br />
77 m 54 – 72 m 70 m 300 m<br />
Distance between buoys 360 m 18-36 m 4.5 km Variable 90-700 m<br />
Yes<br />
No<br />
Float l<strong>in</strong>e length 12 m 0 m 18 m 15-16 m<br />
Branch l<strong>in</strong>e length 19 m 9.1 m 8.2 m 16.5 m 15-24 m<br />
Branch l<strong>in</strong>e material Nylon monofilament Nylon monofilament Polypropylene Nylon<br />
monofilament<br />
Not known<br />
Hooks per basket<br />
(between buoys)<br />
9 5-10 25-35<br />
Tim<strong>in</strong>g of soak Variable Day Night Day for small vessels, night<br />
for distant water vessels<br />
Lightstick frequency Variable None 1 -4 per hook None on small vessels, yes<br />
on floats for large vessels<br />
Weight size <strong>and</strong><br />
location<br />
Variable, usually none<br />
None when target<strong>in</strong>g mahi,<br />
weighted swivels when<br />
target sharks<br />
60 g at<br />
connection of<br />
ma<strong>in</strong>l<strong>in</strong>e <strong>and</strong><br />
float l<strong>in</strong>e<br />
80 g at<br />
connection of<br />
ma<strong>in</strong>l<strong>in</strong>e <strong>and</strong><br />
float l<strong>in</strong>e, <strong>and</strong><br />
65-76 g swivel at<br />
top of leader<br />
Not known<br />
Hook type<br />
J <strong>and</strong> some circle hooks of<br />
various sizes<br />
J 0,1,2,3 (10 o offset)<br />
J17 Ancora<br />
(no offset)<br />
J18 Ancora<br />
(no offset or<br />
10 o offset)<br />
J Mustad 9<br />
(10 o offset)<br />
Not known<br />
Bait type<br />
Squid, pilchards, jack<br />
mackerel,yellowtail, scad,<br />
anchovy, redbait, blue<br />
<strong>and</strong> other mackerel, tooth<br />
whiptails, <strong>and</strong> redfish.<br />
(Live bait =11%)<br />
Sard<strong>in</strong>e, mackerel <strong>and</strong><br />
fly<strong>in</strong>g fish<br />
Squid <strong>and</strong> mackerel<br />
Sard<strong>in</strong>e, pilchard<br />
10
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