Note - Birdlife International /ACAP factsheets for Pelagic Longline Streamer /Bird Scaring Lines are being updated, with new versions expected in 2022.
The following advice is based on the existing factsheets, as well as content from ACAP (2021) ACAP Review of mitigation measures and Best Practice Advice for Reducing the Impact of Pelagic Longline Fisheries on Seabirds. In: ACAP - Twelth Meeting of the Advisory Committee. Online.
Properly designed and deployed BSLs deter birds from sinking baits, dramatically reducing seabird attacks and related mortalities. A bird scaring line runs from a high point at the stern to a device or mechanism that creates drag at its terminus. Brightly coloured streamers hanging from the aerial extent of the line scare birds from flying to and under the line, preventing them from reaching the baited hooks. It is important to note that the BSLs only provide protection to the baited hooks within the area protected by its aerial extent. This is why it is particularly important to use BSLs in combination with weighted branch lines (and night setting), which ensure that the baited hooks have sunk beneath the diving depth of most seabirds beyond the aerial extent of the BSLs. The presence of diving species increases the vulnerability of surface foragers (e.g., albatrosses) due to secondary interactions (i.e. albatrosses attacking baited hooks that are brought back to the surface by diving birds).
Simultaneous use of two BSLs, one on each side of the sinking longline, provides maximum protection from bird attacks under different wind conditions (Melvin et al. 2004; 2013; 2014; Sato et al. 2013). The setup for BSLs should be as follows:
- BSLs should be deployed to maximise the aerial extent, which is a function of vessel speed, height of the attachment point to the vessel, drag, and weight of bird scaring line materials.
- To achieve a minimum recommended aerial extent of 100 m, BSLs should be attached to the vessel such that they are suspended from a point a minimum of 8 m above the water at the stern.
- BSLs should contain a mix of brightly coloured long and short streamers placed at intervals of no more than 5 m. Long streamers should be attached to the line with swivels to prevent streamers from wrapping around the line. All long streamers should reach the sea-surface in calm conditions.
- Baited hooks should be deployed within the area bounded by the two BSLs. If using bait-casting machines, they should be adjusted so as to land baited hooks within the area bounded by the BSLs.
If large vessels use only one BSL, it should be deployed windward of the sinking baits. If baited hooks are set outboard of the wake, the BSL attachment point to the vessel should be positioned several meters outboard of the side of the vessel that baits are deployed.
Ease of deployment and safety
BSLs should be the lightest practical strong fine line. Lines should be attached to the vessel with a barrel swivel to minimise rotation of the line from torque created as it is dragged behind the vessel. Long streamers should be attached with a swivel to prevent them from rolling up onto the BSL. BSLs are at risk of tangling with float lines leading to lost BSLs, interruptions in vessel operations and in some cases lost fishing gear.
BSLs potentially increase the likelihood of entanglements, particularly if the attachment points on davits (tori poles) are insufficiently outboard of vessels. To achieve a minimum aerial extent BSLs should be attached to the vessel such that it is suspended from a point a minimum of 8 m above the water at the stern. Attaching towed objects to the terminus of the in-water extent of bird scaring lines to increase drag has proven problematic in pelagic longline fisheries, as float lines tend to tangle with bird scaring lines. For this reason, the addition of short streamers woven into the in-water extent of the bird scaring line or lengthening or increasing the diameter of the in-water extent, are encouraged to increased drag while minimizing tangles. Weak links (breakaways) should be incorporated into the in-water portion of the line for safety reasons and to minimize operational problems associated with lines becoming tangled.
Vessels <35 m total length should deploy BSLs with a minimum aerial extent of 75 m. To achieve this minimum aerial extent, BSLs should be attached to the vessel such that it is suspended from a point a minimum of 6 m above the water at the stern. Sufficient drag must be created to maximise aerial extent and maintain the line directly behind the vessel during crosswinds. This may be achieved using either towed devices or longer in-water sections (Goad & Debski 2017). Diving species increase vulnerability of surface foragers (albatrosses) due to secondary interactions.
To achieve a minimum recommended aerial extent of 75 m, BSLs should be attached to the vessel such that they are suspended from a point a minimum of 6 m above the water at the stern. Short streamers (>1 m) should be placed at 1 m intervals along the length of the aerial extent. Two designs have been shown to be effective:
(i) a mixed design that includes long and short streamers. Long streamers should be placed at 5 m intervals over at least the first 55 m of the BSL (Domingo et al. 2017). Streamers may be modified over the first 15 m to avoid tangling (Goad & Debski 2017); and,
(ii) a design that only includes short streamers. In all cases, BSLs should be brightly coloured and the lightest practical strong fine line. Lines should be attached to the vessel with a barrel swivel to minimise rotation of the line from torque (created as it is dragged behind the vessel).
Ease of deployment and safety
Sufficient drag must be created to maximise aerial extent and maintain the line directly behind the vessel during crosswinds. To avoid tangling, this is best achieved using a long in-water section of rope or monofilament. Alternatively, short streamers can be tied into the line to ‘bristle’ the line (creating a bottlebrush like configuration) to generate drag while minimising the chance of fouling streamer lines on float lines.
To minimise safety and operational problems it is recommended to use a weak link to allow the bird scaring line to break-away from the vessel in the event of a tangle with the main line, and, a secondary attachment between the bird scaring line and the vessel to allow the tangled bird scaring line to be subsequently attached to mainline and recovered during the haul (Goad & Debski 2017).
- Port inspections to determine the presence of davits (tori poles) to support bird scaring lines, and inspections of bird scaring lines for conformance with design requirements.
- Requires fisheries observers, video surveillance, or at-sea surveillance (e.g. patrol boats or aerial over-flights)
Developing methods that minimise entanglements of the in-water portion of BSLs with longline floats remains the highest priority for research on bird-scaring lines. Other research priorities include: (i) evaluating the effectiveness of one vs. two BSL, (ii) BSL design features including steamer lengths, configurations and materials, especially for very small vessels.
- Birdlife International. 2014. Bycatch Mitigation Fact-sheet 7a (September 2014), Pelagic Longline: Pelagic Longline: Streamer lines (vessels >35 m).
- Birdlife International. 2014. Bycatch Mitigation Fact-sheet 7b (September 2014), Pelagic Longline: Pelagic Longline: Streamer lines (vessels <35 m).
- Boggs, C.H. (2001) Deterring albatrosses from contacting baits during swordfish longline sets. In: Melvin, E.F. and J.K. Parrish (Eds). Seabird Bycatch: Trends, Roadblocks and Solutions. University of Alaska Sea Grant, Fairbanks, Alaska, AK-SG-01-01: 79-94.
- Brothers, N. (1991) Albatross mortality and associated bait loss in the Japanese longline fishery in the Southern Ocean. Biological Conservation, 55: 255-268.
- CCAMLR (2007) Schedule of Conservation Measures in Force, 2007/2008. CCAMLR, Hobart, Australia: 76-80.
- Domingo A., Jimenez, S., Abreu, M., Forsellado, R., and Pons, M. (2011) Effectiveness of tori-line use to reduce seabird bycatch in the Uruguayan pelagic longline fleet. Proyecto Albatros y Petreles - Uruguay. 15 pp.
- Gianuca, D., Peppes, F., Cesar, J., Marques, C. and Neves, T. (2011) The effect of leaded swivel position and light toriline on bird attack rates in Brazilian pelagic longline. Projeto Albatroz. 17 pp.
- Jimenez, S., Domingo, A., Abreu, M. and Brazeiro, A. (2012) Bycatch susceptibility in pelagic longline fisheries: are albatrosses affected by the diving behavious of medium-sized petrels? Aquatic Conservation: Marine and Freshwater Ecosystems. DOI: 10.1002/aqc.2242
- Lokkeborg, S. (2008) Review and assessment of mitigation measures to reduce incidental catch of seabirds in longline, trawl and gillnet fisheries. FAO Fisheries and Aquaculture Circular. No. 1040. Rome, FAO. 2008. 24p.
- Melvin, E., Guy, T. and Read, L.B. (2010) Shrink and defend: A comparison of two streamer line designs in the 2009 South Africa Tuna Fishery. Washington Sea Grant, University of Washington, USA, 29p.
- Melvin, E. F., and Walker, N. (2008) Optimizing tori line designs for pelagic tuna longline fisheries. Report of work under New Zealand Ministry of Fisheries Special Permit 355. Washington Sea Grant. http://www.wsg. washington.edu/mas/ resources/seabird_publications.html
- Melvin, E. F., Heinecken, C., and Guy, T.J. (2009) Optimizing Tori Line Designs for Pelagic Tuna Longline Fisheries: South Africa. Report of work under special permit from the Republic of South Africa Department of Environmental Affairs and Tourism, Marine and Coastal Management Pelagic and High Seas Fishery Management Division. Washington Sea Grant. http://www.wsg.washington.edu/mas/resources/seabird publications.html
- Yokota, K., H. Minami, and M. Kiyota (2008) Direct Comparison of Seabird Avoidance Effect Between two types of tori-lines in experimental longline operations. WCPFC-SC4-2008/EB-WP-7.