Shark Depredation and Unwanted Bycatch in Pelagic Longline

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Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries A7.4. Fishing Gear and Operations There are two distinct pelagic or surface longline gear configurations used in South African waters based on whether the target species is swordfish or tuna. To target swordfish the hooks are generally set shallow (seldom deeper than 40 m) by using short buoylines and branchlines and no line setter. In general lightsticks are also used. This gear configuration generally characterizes the South African domestic fleet. Those that target tuna set the hooks deep (often deeper than 200 m) by using a line setter and long buoylines and branchlines. Lightsticks are seldom used. This gear configuration is generally employed by the Japanese and Taiwanese fleets. Fig. A7.1. Fishing effort by foreign vessels (Japanese and Taiwanese) operating in South African pelagic longline fishery (1996-2002) under bilateral agreement. Fig. A7.2. Fishing effort by domestic vessels operating in South African pelagic longline fishery (2000-2005). Fig. A7.3. Fishing effort by foreign vessels operating under joint-venture agreements in South African pelagic longline fishery (2004-2005). There were on average 17 (range 1-26) vessels in the domestic fleet between 1997-2003. Thirty vessels carried an observer at least during this time period. This description of the fishery is derived from this subset of the fleet (n=615 sets on 70 trips) as well as information provided in interviews. Sampled vessels vary in size (average 31 m, range 19-56 m, std dev 7.9 m) and carry an average of 18 (range 6-31, std dev 5) crew members. Trips (n=70) are on average 14 (range 5-38, std dev 5.8) days. In general a mainline, which could be over 50 miles, is usually made of monofilament nylon. It is usually set between late afternoon and midnight (43% set in the dark, 2% in the light and 55% during twilight) and is allowed to soak until dawn (note: dark/light = start to finish in the dark/light, twilight = start in the dark or light and end in the other). The line is kept close to the surface by numerous buoys which are attached to the mainline via buoylines at an average of 194 m (range 46-370 m, std dev 108) apart and are on average 20 m (range 10-37 m, std dev 3 m) long. Additional radio or light buoys are also used to locate the line. There are between 20 and 472 (average 272, std dev 100) buoys on a line and on average five (range 3-30, std dev 3) branchlines or snoods between buoys. On average 1300 (range 1000-2500) hooks are attached to the mainline the branchlines. Branchlines are spaced evenly along the mainline at an average of 42 m (range 17-65 m, std dev 15) apart. A typical South African flagged pelagic longliner makes up their branchline to the following specifications (Table A7.1): an upper section of approximately 18 m, a swivel (usually 60-80g) and a lightstick and then a lower section of approximately 2 m ending in a baited hook. Eighty nine percent of observed vessels used squid as bait, with the remaining 11% using a combination of squid and between 8-75% fish bait (pilchard, mackerel). This is consistent with interview results. None was recorded using live bait. According to observer data 23% of vessels did not use light sticks (most likely those targeting tuna), 5% used light sticks on less than 50% of their branchlines, 3% used light sticks on 50% of their branchlines, 12% used light sticks on between 51-99% of their branchlines and 57% used light sticks on 100% of their branchlines. All those interviewed said they always use light sticks. 10% of observed vessels used a line setter. In general the line is set at an average speed of 8 knots. 114
South Africa Pelagic Longline Tuna and Swordfish Fishery Table A7.1. Description of fishing gear. Fishing Gear and Method South African Vessels Asian Vessels Trip duration 10-15 days 45 days (usually longer when observers not on board) No. of sets per trip 8-15 sets 40 sets No. of trips per year Variable Most of the year Fishing grounds Mainly on continental shelf off the West coast and northeast coast Mainly on Agulhas Bank & continental shelf on East coast Fishing season(s) All year All year Mainline material Mainly Monofilament nylon Mainly Monofilament nylon Mainline length 50 miles Mainline deployment Stern Stern Distance between buoys Distance from buoy to mainline (float line length) 200 meters 20 meters Average branch line length 20 meters (2 sections) 38 meters (3 sections) Branch line material Mainly Monofilament Multi- & Monofilament & braid with lead core Wire trace or leader on branch lines Not permitted Not permitted No. of hooks between buoys 5 Average maximum depth of hooks when set Average maximum depth of mainline when set 60-70 meters 40-50 meters Branch line sink rate 0.24m/sec (with 60g) 0.12m/sec (no weight) Timing of set 43% dark, 2% light, 55% twilight 43% dark, 2% light, 55% twilight Lightstick use Yes No Number of hooks per set 1000-1500 1000-2500 Hook setting interval 40 meters Radio beacons Yes Yes Hook type J hook J hook Weight size and location 60-80 grams swivels 2 meters above the hook None Clip size and type Snap-Jap 3.8 x 130 Bait type Mainly Squid Squid and fish (e.g. Sardine) Number of crew Average of 18 Average of 20 Vessel Monitoring System Yes Yes 115
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Shark Depredation and Unwanted Byca
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Contents Summary and Conclusions 1
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Contents Appendix 3. Fiji Pelagic L
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Contents Appendix 8. USA Hawaii Lon
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Chapter 1 Introduction and Methods
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Introduction and Methods 1.2. Metho
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Fishing Gear and Operational Charac
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Fishing Gear and Operational Charac
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Shark Catch Rates and Disposition T
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Chapter 4 National and Internationa
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National and International Measures
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Economic, Practical, Ecological and
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Economic, Practical, Ecological and
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Chapter 6 Industry Attitudes and Pr
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Industry Attitudes and Practices Lo
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Industry Attitudes and Practices Fi
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Chapter 7 Potential of Deterrents,
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Potential of Deterrents, Hotspot Av
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References Campana, S.E., L. Marks,
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References Neves dos Santos, M., Ga
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Page 99 and 100: Appendix 5 Japan Pelagic Longline F
Page 101 and 102: Japan Pelagic Longline Fisheries Fi
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Page 105 and 106: Japan Pelagic Longline Fisheries Ta
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Page 113 and 114: Japan Pelagic Longline Fisheries A5
Page 115 and 116: Appendix 6 Peru Artisanal Mahimahi
Page 117 and 118: Peru Artisanal Mahimahi And Shark L
Page 127: Appendix 7 South Africa Pelagic Lon
Page 131 and 132: South Africa Pelagic Longline Tuna
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Page 135 and 136: Appendix 8 USA Hawaii-based Pelagic
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Page 147 and 148: Appendix 9 USA Atlantic, Gulf of Me
Page 149 and 150: USA Atlantic, Gulf of Mexico and Ca
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Shark Depredation and Unwanted Bycatch in Pelagic Longline

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