Improving tori line performance in small- vessel longline fisheries - … 6.3.3 WCPFC... · 1...
Transcript of Improving tori line performance in small- vessel longline fisheries - … 6.3.3 WCPFC... · 1...
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Improving tori line performance in small-
vessel longline fisheries
WCPFC-SC12-2016/EB-WP-09
Johanna Pierre1, Dave Goad2, Igor Debski3,
and Kirstie Knowles3
1JPEC Ltd, 2Vita Maris Ltd, 3Department of Conservation
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Tori lines
• One of the most thoroughly tested
seabird bycatch reduction methods
• Proven to be effective (in
combination with line weighting and
night setting) in reducing seabird
bycatch in both trawl and longline
fisheries.
• Requirement of CMM 2015-03.
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Best Practice for vessels <35m
Examples of optimal streamer lines for pelagic longline fisheries (designs
taken from (a) Gianuca et al., 2011 and (b) Domingo et al., 2011).
Source: Birdlife International and ACAP Bycatch Mitigation factsheet 7b
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Considerations for small vessels
tori lines
• Aerial extent:
- setting speeds
- height of attachment point
- drag
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Optimal aerial extent of tori line
Bait Access Weighted
Branch lines
Bait Access
Unweighted
Branch lines
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Considerations for small vessels
tori lines
• Aerial extent:
- setting speeds
- height of attachment point
- drag
• Tangling – in water and during
storage
• Crew safety
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Study objective
• To develop improved tori lines that
are specifically optimized for safe
and effective use on small vessels.
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At sea testing
• Worked with vessel
operators to identify issues
& possible solutions
• Trials at seas on 4 different
fishing vessels
Vessel trails (3 vessels):
- 7 designs on Vessel A
- 8 designs on Vessel B
- 7 designs on Vessel C
• Principle measure of
effectiveness = aerial
extent
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Results at sea
Preliminary drag testing:
• Most designs tested did not generate sufficient
drag for 70m aerial extent
• Low speeds worst
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Revised designs
Figure 7. Tori line 8 showing the large road cone comprising the
in-water section and the splash it created at 4 knots. The rope
used to measure aerial extent (marked with floats at 5-m
intervals) is visible on the left.
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Revised designs
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Storage and attachment
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Recommended baseline for tori
line designs
• Backbone: 3mm diameter Dyneema, with 70m+
aerial extent section
• Streamers: single long lightweight streamers
(5mm) placed at 3.5m intervals (starting at 5m
to avoid tangling with fishing gear)
• Pole: 52mm fibretube pole to deploy tori line at
6m+ height.
• Weak links for safety and operational reasons
e.g. attaching tori line to pole.
• In water section: monofilament least prone to
tangling (adding small cones to create more
drag if required)
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Key new materials
• Thin plastic tubing
(5mm) = ideal
lightweight material
• Small and large
manufactured plastic
cones – provided easily
modified drag
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Summary
• Best practice tori line designs with
streamers are viable on small
vessels.
• There are endless design options
that meet best practice guidelines.
• Further research is warranted,
including at-sea trials under a range
of weather conditions.
• We are very keen to work with
member scientists on comparative
studies.
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Recommendations
• note the tori line options reported here,
developed especially for small longline
vessels, and recognise that they may be
useful for vessel operators to implement
practical and effective tori lines to meet
current required specifications.
• consider these tori line designs during the
review or development of any updated tori
line specifications, as will be required for
the review of specifications set out in CMM
2015-03.
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Acknowledgements
• Skippers and crew of the test vessels
• Fisheries Inshore NZ
• Deep Water Group
• KilwellSports Ltd
• Supply Services Ltd
• Beauline International Ltd
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Questions?
Photo: Phillip Griffin