Collaborative mitigation research for pelagic longline fisheries in South Africa

Ed Melvin and Troy Guy,Washington Sea Grant, University of Washington,

andLorraine B. Read ,

TerraStat Consulting Group

Principles of Collaborative Research

• Test fishermen’s ideas with fishermen – fishermen invested in the

outcome

• Demonstrate mitigation strategies reduce bird interactions and are

practical and safe

• Results in proof at two level:

– Fishermen know measures work – seen with their own eyes

– Managers know measures work – researchers produce solid scientific

proof with data and analysis

Research Goal – collaborative research in pelagic longline fisheries

• Develop a bird-scaring line (tori line) for pelagic longline fisheries for

application in tRFMO fisheries

• Test tori lines where bird interaction are very high and most difficult

– Southern Hemisphere

• Do research on fishing vessels typical of the high-seas Asian fleets

• Do research in a fishery with strong support from fishery managers,

fishing industry, observer program, and other partners

South African Tuna Joint Venture Fishery

• Three year research program

• Year one: pilot studies in New Zealand and South

Africa

• Year two: Test two streamer line designs and introduce

branchline weighting

• Year three: Test weighted branchlines and night

setting with two hybrid streamer lines

Unweighted branchlines sink 300 mbeyond the vessel – an area too big to protect

with bird scaring lines

300 m bait access

• Clear need to weight branchlines• Shrink and Defend: Shrink the area astern that requires defending with

streamer lines

Unprotected by bird scaring line

Hybrid Bird-Scaring Lines: The ConceptAerial extent is the section that scares birds

- must span the area birds are vulnerable to hooking

Bait Access

100 m achieved with experimental weighting in 2009

(60 g w/in 2 m of the hook)

Packing straps create drag to maintain aerial extent of 100 m

2010 Comparisons• Three mitigation measures

– W vs. UW branchlines

– Night vs. Day

– With two hybrid streamer lines

• Two vessels production fishing

• South Africa in Austral Winter

– worst case interactions with aggressive A & P

Double-Weight Branchline Sectionalternative to weighted sivels which are potentially dangerous

Coated Wire Kodo

Developed by Fishing master Yamazaki-san

1m to 1.5 m weighted section inserted 2 m above the hook

Total weight 65 to 70 gWithin 3 to 3.5 m of the hook

Multiple weights – one slidingNon-stretch weighted lines (vs mono = rubber band)

weighted section

weights

lead-core line (Kodo)

monofilament

monofilament

Hybrid Streamer Line

Aerial Extent = 100m In-Water Extent = 100m

200m100m50m 150m

Attack rate diving seabirds: weighted vs. un-weighted

0,000

5,000

10,000

15,000

20,000

25,000

25 50 75 100 125 150 200

Ave

rage

att

acks

per

10

00

ho

oks

Distance Astern (m)

Unweighted Weighted

aerial extent

Bird Mortality

Fish Catch

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

Billfis

h

es Albacore Bigeye Yellowfin Total

un-weighted weighted

generalized linear fixed effects model with observation and day as random effects

Fis

h/ 1

,00

0 h

oo

ks

Weighted Branchlines + 2 SLs

• Sink faster ~ 70 m

• fish catch little to no effect (two years now)

• seabird mortality rate reduced 8 fold;

• Attack rates reduced 4 fold

• Night mortality = o

• Relatively safe - no injuries

Relevance to tRFMOs2 Hybrid streamer lines (100 m aerial extent)

+

weighted branchlines

+

night setting

=

Best-practice mitigation in SA EEZ and other white-chinned petrel

dominated systems/ southern hemisphere

Acknowledgments

• The Japan Tuna Fisheries Co-operative Association

• South Africa Marine and Coastal Management Pelagic and High Seas

Fisheries Management Division

• Tuna South Africa

• Japan Marine and CapFish

• The David and Lucile Packard Foundation and Washington Sea Grant

• BirdLife Albatross Task Force and WWF