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Seabird bycatch mitigation measures

View of trawl cables from the winches

Image: Peter Exley

Fisheries bycatch is the single greatest threat facing many seabird populations, but it is both unnecessary and preventable.

In fact, it not only has disastrous consequences for the birds, but also renders fishing operations less efficient.

Fortunately, there are simple and effective solutions that can prevent seabird bycatch in longline and trawl fisheries. You can find out more from our Introduction to seabird bycatch mitigation measures download (below).

There are also a series of 14 factsheets available for you to download (below) describing the range of potential mitigation measures available to reduce seabird bycatch in longline and trawl fisheries.

The sheets assess the effectiveness of each measure, highlight their limitations and strengths, and make best practice recommendations for their effective adoption. They are designed to help decision-makers choose the most appropriate measures for their longline and trawl fisheries.

1. Demersal Longline: Streamer lines

1. Demersal Longline: Streamer lines

215Kb, PDF

Streamer lines are the most commonly prescribed mitigation measures for longline fisheries and are regarded as one of the most effective known mitigation measures (a primary measure). Streamer lines are cheap, simple to use and do not require modification of the fishing gear.

Date: 8 October 2012

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2. Demersal Longline: Line weighting – external weights

2. Demersal Longline: Line weighting – external weights

183Kb, PDF

Seabirds are vulnerable to mortality during the short period between hooks leaving the vessel and sinking beyond the bird's diving range. Line weighting is an essential component of seabird bycatch mitigation strategies, being one of the more effective known mitigation measures (a primary measure).

Date: 8 October 2012

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3. Demersal Longline: Integrated weight longlines

3. Demersal Longline: Integrated weight longlines

185Kb, PDF

Line weighting is an essential component of seabird bycatch mitigation strategies, being one of the most effective known mitigation measures (a primary measure). Best practice weighting regimes should result in rapid initial line sink rates that will reduce the likelihood of seabird bycatch. Integrated weight lines with lead beads in the core were developed to address this problem.

Date: 8 October 2012

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4. Demersal Longline: Line weighting – Chilean System

4. Demersal Longline: Line weighting – Chilean System

226Kb, PDF

Seabirds are vulnerable to mortality on longline hooks during the short period between hooks leaving the vessel and sinking beyond the bird’s diving range. The Chilean System was developed primarily to combat the problem of depredation by cetaceans, however, the configuration of the gear leads to very high initial hook sink rates, which results in near zero seabird bycatch rates.

Date: 8 October 2012

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5. Demersal and Pelagic Longline: Night-setting

5. Demersal and Pelagic Longline: Night-setting

149Kb, PDF

Night-setting is one of the few mitigation measures that is equally applicable to both demersal and pelagic longline fisheries.

Date: 8 October 2012

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6. Demersal Longline: Underwater setting chute

6. Demersal Longline: Underwater setting chute

156Kb, PDF

Seabirds are at greatest risk of becoming hooked and drowned when baited hooks are at, or within a few metres of, the surface. In theory, setting hooks below the surface of the water should greatly reduce the likelihood of catching seabirds.

Date: 8 October 2012

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7a. Pelagic Longline: Streamer lines large vessels

7a. Pelagic Longline: Streamer lines large vessels

204Kb, PDF

Streamer lines are the most commonly prescribed seabird bycatch mitigation measures for longline fisheries and one of the most effective (a primary measure). Streamer lines were an innovation of Japanese tuna fishermen to prevent bait loss to birds. They are inexpensive, simple and require no modification to fishing gear.

Date: 8 October 2012

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8. Pelagic Longline: Line weighting

8. Pelagic Longline: Line weighting

249Kb, PDF

Line weighting is one of the most effective known mitigation measures (a primary measure). It is widely applicable to pelagic longline fishing, and has been demonstrated to lead to reductions in seabird bycatch. It is recommended that it be used in combination with streamer lines, night setting and other measures as required.

Date: 8 October 2012

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9. Pelagic Longline: Side-setting

9. Pelagic Longline: Side-setting

155Kb, PDF

Side-setting appears to be effective in the waters of the North Pacific where it was developed. The ability to generalise its use across other oceans, with a higher diversity of seabirds with greater diving capabilities and more demanding sea conditions, remains untested.

Date: 8 October 2012

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10. Pelagic Longline: Blue-dyed bait (squid)

10. Pelagic Longline: Blue-dyed bait (squid)

157Kb, PDF

Blue-dyed bait is a measure under development and, while there are some promising results, there is some uncertainty about its long-term effectiveness at reducing seabird bycatch and the practicality of widespread application.

Date: 8 October 2012

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11. Pelagic Longline: Bait caster and line shooter

11. Pelagic Longline: Bait caster and line shooter

148Kb, PDF

Some measures, used by fishermen to improve the economic or operational efficiency of fishing, are also considered effective measures to reduce seabird bycatch. Such measures may contribute to reducing seabird bycatch when used in combination with a suite of other measures, but lack efficacy when used in isolation.

Date: 8 October 2012

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12. Demersal and Pelagic Longline: Haul mitigation

12. Demersal and Pelagic Longline: Haul mitigation

180Kb, PDF

Seabirds are attracted to longliners during hauling to feed on discards, offal and spent bait. Birds can easily become hooked, in the bill, foot or wing, as the line returns to the surface or swallow hooks left in discards or bait. These interactions are rarely lethal at the time but the injuries sustained could have serious implications for the long-term survival of the individuals concerned.

Date: 8 October 2012

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13. Trawl Fisheries: Warp strike

13. Trawl Fisheries: Warp strike

194Kb, PDF

In recent years, dedicated seabird observers on trawl vessels have identified significant bycatch problems. These fall into two categories, net entanglement (Factsheet 14) and collisions with cables, predominantly those used to tow the net (warp strikes), but also net monitoring equipment.

Date: 8 October 2012

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14. Trawl Fisheries: net entanglement

14. Trawl Fisheries: net entanglement

144Kb, PDF

In recent years, dedicated seabird observers on trawl vessels have identified significant bycatch problems. These fall into two categories, collisions with the cables used to tow the net (Warp strike, Factsheet 13) and net entanglement.

Date: 8 October 2012

Download

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