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 A2.2. Fish<strong>in</strong>g gear characteristics of the Chilean longl<strong>in</strong>e fishery (from surveys <strong>and</strong> Barria et al., 2006).<br />
Gear Characteristic<br />
Artisanal Mahi Mahi<br />
Spanish System<br />
Industrial swordfish<br />
American System<br />
Ma<strong>in</strong>l<strong>in</strong>e material<br />
Ma<strong>in</strong>l<strong>in</strong>e length<br />
Multifilament<br />
4-5mm Ø<br />
1500-2000 fathoms<br />
(2.7–3.7 km)<br />
Polypropylene<br />
Multifilament<br />
6mm Ø<br />
45 nautical miles<br />
(83 km)<br />
Monofilament<br />
3.5mm Ø<br />
35-55 nautical miles<br />
(64-101 km)<br />
Ma<strong>in</strong>l<strong>in</strong>e deployment Superficial Mid-water Mid-water<br />
Distance between buoys 18-36 m (10-20 fm) 4.5 km varies<br />
Distance from buoy to ma<strong>in</strong>l<strong>in</strong>e<br />
(float l<strong>in</strong>e length)<br />
NA 10 fathoms 10 fathoms<br />
Average branch l<strong>in</strong>e length 9.1 m (5 fm) 8.2 m (4.5 fm) 16.5 m (9 fm)<br />
Branch l<strong>in</strong>e material Monofilament polypropylene Monofilament 20mm Ø<br />
Wire trace or leader on branch l<strong>in</strong>es Sometimes Yes or no Yes<br />
Number of hooks between buoys 1 110 220-250<br />
Average maximum depth of hooks when set 6-8 fathoms 70m 70m<br />
Average maximum depth of ma<strong>in</strong>l<strong>in</strong>e when set Superficial 50m 50m<br />
Ma<strong>in</strong>l<strong>in</strong>e s<strong>in</strong>k rate No <strong>in</strong>formation No <strong>in</strong>formation 90 m <strong>in</strong> 16 seconds<br />
Tim<strong>in</strong>g of set, soak, <strong>and</strong> haul Set: 7 AM (for 2-6 h)<br />
Soak: survey<strong>in</strong>g the l<strong>in</strong>e several<br />
times a day<br />
Haul: 4 to 5 PM (for 3-4 h)<br />
Set: 6-8 PM (for 4 h)<br />
Soak: 20h<br />
Haul: 8AM (for 8 h)<br />
Set: 6PM (for 4 h)<br />
Soak: 8h<br />
Haul: 8AM (for 6 h)<br />
Lightstick use No Plastic polymer chemical or battery<br />
Number of hooks per set 100-350 1500 1200-2000<br />
Hook sett<strong>in</strong>g <strong>in</strong>terval No <strong>in</strong>formation No <strong>in</strong>formation 8-16 seconds<br />
Radio beacons No Yes Yes<br />
Hook type J 0,1,2,3 (10 o offset) J17 Ancora (no offset)<br />
J18 Ancora (no offset or 10 o offset)<br />
Weight size <strong>and</strong> location NA 60 g. at connection of ma<strong>in</strong>l<strong>in</strong>e<br />
with float l<strong>in</strong>e<br />
Clip size <strong>and</strong> type NA 350S 350S<br />
J Mustad 9 (10 o offset)<br />
80 g. at connection of ma<strong>in</strong>l<strong>in</strong>e<br />
with float l<strong>in</strong>e 65-75 g. swivel at<br />
top of leader<br />
Bait type Mackerel <strong>and</strong> sard<strong>in</strong>e Squid or mackerel Squid <strong>and</strong> mackerel<br />
Number of crew 2-3 12-15 8-10<br />
Vessel Monitor<strong>in</strong>g System No No No<br />
Table A2.3. Catch per unit effort of sharks of the artisanal shark fleet, 2003-2005 (Barria et al., 2006).<br />
Yield (g/hook)<br />
2003 2004 2005<br />
Month Mako Blue Total Mako Blue Total Mako Blue Total<br />
Jan 194.3 22.7 217.0 245.6 8.5 254.1 314.6 9.5 324.1<br />
Feb 265.2 22.5 287.7 401.3 9.1 410.5 301.8 8.1 309.9<br />
Mar 382.2 47.8 430.0 236.5 17.3 253.8 269.1 55.8 325.0<br />
Apr 281.3 58.8 340.1 290.6 38.9 329.5 232.6 69.1 301.7<br />
May 154.2 28.1 182.3 249.4 35.0 284.4 261.8 85.9 347.7<br />
Jun 160.3 57.1 217.5 168.7 31.7 200.4 85.4 68.8 154.2<br />
Jul 27.5 11.7 39.3 78.9 82.6 161.4 74.2 37.0 111.3<br />
Aug 52.9 29.6 82.4 75.6 97.5 173.1 91.1 55.8 146.9<br />
Sep 141.5 50.6 192.1 119.0 62.2 181.2 45.8 119.1 164.9<br />
Oct 172.7 78.1 250.8 183.9 49.5 233.5 58.9 147.6 206.5<br />
Nov 188.6 37.5 226.2 283.5 40.8 324.3 295.5 71.9 367.5<br />
Dec 208.9 15.5 224.3 224.0 14.1 238.1 160.4 25.6 186.0<br />
Total 216.9 37.5 254.4 249.8 26.9 276.7 235.9 41.8 277.7<br />
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