Collaborative mitigation research for pelagic longline fisheries in South Africa
Ed Melvin and Troy Guy, Washington Sea Grant, University of Washington,
and Lorraine 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 m beyond the vessel – an area too big to protect with bird scaring lines
Unprotected by bird scaring line
300 m bait access • Clear need to weight branchlines • Shrink and Defend: Shrink the area astern that requires defending with streamer lines
Hybrid Bird-Scaring Lines: The Concept Aerial 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 Section alternative to weighted sivels which are potentially dangerous
Developed by Fishing master Yamazaki-san Coated Wire
Kodo
1m to 1.5 m weighted section inserted 2 m above the hook Total weight 65 to 70 g Within 3 to 3.5 m of the hook Multiple weights – one sliding Non-stretch weighted lines (vs mono = rubber band)
monofilament lead-core line (Kodo)
weighted section
weights
monofilament
Hybrid Streamer Line
Aerial Extent = 100m 50m
In-Water Extent = 100m 100m
150m
200m
Attack rate diving seabirds: weighted vs. un-weighted
25,000
aerial extent Average attacks per 1000 hooks
20,000 Unweighted
Weighted
15,000
10,000
5,000
0,000 25
50
75
100
Distance Astern (m)
125
150
200
Bird Mortality
Fish Catch
Fish/ 1,000 hooks
16.00 h 14.00
un-weighted
12.00
weighted
10.00 8.00 6.00 4.00 2.00 0.00 Billfis es
Albacore
Bigeye
Yellowfin
Total
generalized linear fixed effects model with observation and day as random effects
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 tRFMOs 2 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