hauling mitigation for small longline vessels - doc.govt.nz
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Hauling mitigation for small longline vessels
Presentation to Conservation Services Programme Technical Working Group 27 May 2021
D. Goad* and T. Peatman†
Contract reference 18302 MIT2018-02
* Vita Maris † Independent Fisheries Consultant
1
Background
• To date most focus has been on mitigating dead (set) captures
• 33% BLL and 16% SLL captures alive
• Tend to fly off, historically not perceived by fishers as serious
• Fate unknown, ‘counted’ as 0.5 in the risk assessment
• H&S risk to crew, and loss of time
• Easier task than setting mitigation = smaller area, beside the boat
2
Objective
To develop effective and practical options to mitigate the capture of seabirds on haul in small vessel demersal and pelagic longline fisheries.
3
Methods
• Design / fit devices
• Sea trips to trial devices and collect data
• Comparing mitigation and no mitigation treatments using real time
observations and Go Pro video
• Also collected a longer-term dataset from BLL EM footage
• Captures are rare – need to use a proxy for risk
(birds in or moving into a risky area)
4
Methods – At sea data collection
4 m
1 m
Vessel T (pelagic longline)
Vessel C (pelagic longline)
Vessel J (demersal longline)
4 m
3 m
Bait 1 %salted
(y/n)
Swell
height (m)Bait 2 %salted
(y/n)
Behaviour counts
Species
< 100 m in the air
< 100 m on the water
0 - 3 m from discard point
Comments
Wind directionWind speed
Observation number Treatment Start Stop
Abundance counts
Swell direction
Submerged dives
Start time End time
Contacts with baited hook
Contacts with line / snood
Birds behind device
Birds forward of device
Hooks hauled
Baits returned
Discarded baits
Discarded fish
Discarded offal
Visibility score
< 1.5 m from line
1.5 - 3 m from line
5
Methods – Data analysis
• Data exploration – box-whisker plots by observation period
• Bayesian MCMC models for real time data sets and EM dataset
• Real time - Rate of seabirds entering the area forward of the mitigation,
defined as numbers per hook per bird within 100 m for pelagic longlines,
and numbers per minute per bird within 100 m for demersal longlines.
• Observations with no seabirds within 100 m of the vessel were excluded
from the modelled dataset. This removed all (pelagic longline) fishing
events where gear was hauled at night time.
• EM - Rate of seabirds moving into the area forward of the mitigation
device per minute.6
Results - Devices
• Surface longline
• Demersal longline
7
Results – Demersal longline different data sources
8
Moving into area
forward of mitigation
from astern
Abundance <100 m
in the air (black)
and water (grey)
MitigationControl
Moving into area
forward of mitigation
from ahead
Moving into area
forward of mitigation
from side
Maximum count
in area aft
of mitigation
Maximum count
in area forward
of mitigation
12
6
0
60
30
0
12
6
0
12
6
0
12
6
0
12
6
0
12
6
0
12
6
0
12
6
0
12
6
0
12
6
0
12
6
0
28 1 2 432170 14
Wind strength (knots)
Time (observation period) Time (observation period)
Time (observation period)
Wind direction frequency
(n observations)
Wind direction
relative to vessel.
Hauling on starboard side
Real time counts Counts from Go Pro footage Counts from EM footage
Results – Demersal longline model real time data
-1.5 -1.0 -0.5 0
Linear predictor
Treatment (mitigation)P
opula
tion e
ffects
6
5
4
3
0 5 10 15
Wind strength (knots)
Lin
ear
pre
dic
tor
9
Results – Demersal longline EM footage
10
Results – Demersal longline EM data
11
Control
Mitigation
0
5
10
15
0
5
10
15
Count of birds moving into forward area, from astern
Count of birds moving into forward area, from ahead
20
25
30
By treatment block (number of minutes / observations)66 57 40 65 36 94 135 236 217 234 24 86 149 10 150 12 226173 102 145 14455 60 61 74 238 224219 70 272 6 39 132 183
Results – Demersal longline model EM data
-1.5 -1.0 -0.5 0
Linear predictor
Treatment (mitigation)
Effects
12
Results - Demersal longline float
Control
During hauling of intermediate float
Maximum count of birds
in area forward of device
Maximum count of birds
in area aft of device
Count of birds moving
into forward area,
from astern
Count of birds moving
into forward area,
from ahead
0
10
20
0
10
20
40
0
10
20
30
0
10
20
13
Results - Demersal longline float
-3-4 -1-2 0
Linear predictor
No mitigation : Control area
Mitigation : Control area
No mitigation : Float area
Mitigation : Float area
Mitig
ation
:A
rea c
om
bin
ation
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Results – Bird behaviour
1
1
11
2
2
2
3
3
3
3
Wind Wind Wind WindWind
2
1
3
2
1
2 2
3 3
WindWind
11
A B C D E
F G H
15
Results – Pelagic longline real time vs Go Pro video
Control Mitigation
Haul 1 Haul 2 Haul 3 Haul 4 Haul 1 Haul 2 Haul 3 Haul 4
0
50
100
150
200
250
0
50
100
150
200
250
Count of birds moving into both areas in the air and those landing on the water
Real time Video
34n 25 36 27 11 11 15 21 4 17 12 16 13 5 34 25 36 27 11 11 15 21 4 17 12 16 13 5
16
Results – Pelagic longline - summer
Haul 1
0
34 25 36 27 11 11 15 21 4 17 12 16 13 5
28 2 4 62170 14
20
40
60
80
0
Abundance
Count
of
birds m
ovin
g into
are
a
50
large birds
small birds
100
Control
Mitigation
Wind strength (knots) Wind direction frequency (n observations)Wind direction
relative to vessel.
Hauling on port side
n baskets
100
120
140
Haul 2 Haul 3 Haul 4
17
Results – Pelagic longline - winter
28 2 4 62170
Haul
66n 6 6 6 6 4 4 4 4 43 6 6 6 6 6 6 6 6 5 6 6 7 6 5 6 6 6 82
Abundance
Counts
0
0
10
20
30
2
4
6
8
10
1 2 3 4 5 6
14
Wind strength (knots) Wind direction frequency (n observations)Wind direction
relative to vessel.
Hauling on straboard side 18
Results – Pelagic longline
-6 -4 -2 0
Linear predictor
Treatment (mitigation)
Target (STN)
Popula
tion e
ffects
50 60 70 10080 90
Proportion squid bait
0 25 50 10075
Proportion small birds
8
7
6
5Lin
ear
pre
dic
tor
8
10
6
4
Lin
ear
pre
dic
tor
19
Conclusions
• Results and feedback from skippers show that the simple, cheap, and hassle-
free designs presented here are acceptable to fishers and reduce, but not
eliminate, risk to birds during hauling.
• Encourage uptake across the fleet
• On some demersal longliners it may be possible to use a towed float
• The nature of pelagic longline gear provides a much larger area in which birds
can access hooks. It is hard to mitigate birds diving in front of the vessel.
• The use of video footage, including EM derived footage, was adequate for
assessing the efficacy of mitigation. Quantifying mitigation use and capturing
this data when routinely reviewing EM data should be encouraged.
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Acknowledgements
• Owners, skippers, and crew of the vessels involved for their
openness, time and patience, good company, good food,
professionalism, and can-do attitudes.
• Lyndsey, Igor, and Trude at DOC for help and support
throughout the project, and review of the report.
• David Middleton, Snapit, and Teem Fish for arranging
access to, and help with using, the EM footage
• This project was funded by the Department of
Conservation’s Conservation Services Programme
principally through a levy on the quota holders of relevant
commercial fisheries.
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