Addressing Whale Depredation in Longline Fisheries: A Global Perspective

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Whale depredation on longline fisheries is a pervasive issue affecting various types of fishing practices like pelagic and demersal longline fisheries. Different approaches to mitigate depredation include research on whale populations, fishing practice adjustments, and technological solutions. Collaboration between stakeholders, including fishing companies, scientists, and fishery managers, is essential in finding sustainable solutions. Future efforts should focus on understanding key priorities, fishery needs, and planning actions for the next two years to address this global challenge effectively.

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Whale depredation on longline fisheries A worldwide issue

Whale depredation on longline fisheries A worldwide issue Tuna and swordfish pelagic longline fisheries

Whale depredation on longline fisheries A worldwide issue Sablefish demersal longline fisheries Toothfish demersal longline fisheries

What depredates?

What are the depredation levels? traditional Trotline Trotline Traditional Trotline Traditional Traditional Traditional

What are the depredation levels? 25% sets Avg. (NMFS) 30% Catch Avg. 5% Catch Avg. 15% sets 10% Catch 15% Catch 5% Catch Avg. <3% sets

1) Presence/absence 2) Photo-identification 3) tracking/diving data 4) Biopsy sampling 5) Acoustics 6) Research on depredating whale populations Mitigating depredation Fishing practices Technological systems 1) Avoidance (communication network, displacement, seasonality, spatial patterns) 2) Operational factors (hauling speed, short lines, etc.) 3) Vessel vs. Skipper effects 4) 1) Acoustic Harrassment Devices 2) Fish protection devices 3) Gear modification (e.g. hauling speed) 4) Decoys 5) Bubbler 6) Towed array 7)

Combination of approaches Research on depredating whale populations Mitigating depredation Fishing practices Technological systems

Collaborative work Fishing companies, skippers and crew Scientists Research on depredating whale populations Mitigating depredation Fishing practices Technological systems Fishery managers Administration/go vernments

Whats next 1) What we have learnt so far and what are the key priorities? 2) What are the needs of each fishery? What are they planning to do over the next 2 years? Outcomes of the workshop - Peer reviewed paper = global review of depredation on demersal longlines and mitigation solution - CCAMLR paper - Guidelines on data collection

Research on depredating populations Absence / presence data Spatial patterns Areas of high/low depredation Link with ecological factors S. Georgia, Crozet, Kerguelen, HIMI, W Alaska Time patterns Seasonnality Falklands, S.Georgia, Crozet, Kerguelen, HIMI Trend (spread?)

Research on depredating populations Photo-identification data Number of depredating individuals Effects on population demographics Identification of Specialized vs. opportunistic individuals Within population spread of depredation, learning pathways based on social affinity Site fidelity

Research on depredating populations Satellite tracking data and diving behaviour Areas of natural presence Overlap with fishing grounds Switch to depredation, detection range Movements around vessels, swimming speed Depth of interaction (soaking? Hauling?)

Research on depredating populations Biopsy sampling Natural diet, part of the target fish species in diet? Genetics Ecological factors influencing the switch of depredation