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

14

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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