Marine Mammal Bycatch in Gillnets

Fisheries bycatch is the principal threat to many marine mammals. In some cases, bycatch reduction devices have been shown to mitigate the bycatch of non-target species, but the scale of the problem outpaces progress in finding solutions. In particular, bycatch in coastal gillnet fisheries is one of the most immediate threats facing many marine mammal species worldwide, including the Gulf of California porpoise (or vaquita, Neophocoena sinus), dugong (Dugong dugon), and Australian sea lion (Neophoca cinerea).

In October 2011, the Consortium for Wildlife Bycatch Reduction held a workshop to assess the state of the art in gillnet bycatch mitigation techniques, develop recommendatins for best practices, and identify research priorities for the future.

The Consortium invited presentations from experts on the status of marine mammal bycatch in gillnets and mitigation techniques: acoustic deterrents, non-acoustic gear modifications, time-area closures, and gear switching.


A Theme Section of Endangered Species Research features papers that resulted from this workshop. 

Techniques for Reducing Bycatch of Marine Mammals in Gillnets

Kindt-Larsen L, Dalskov J, Stage B, Larsen F. 2013. Observing incidental harbour porpoise Phocoena phocoena bycatch by remote electronic monitoring. ESR 19: 75-83 

Niemi M, Auttila M, Viljanen M, Kunnasranta M. 2013. Movement data and their application for assessing the current distribution and conservation needs of the Saimaa ringed seal. ESR 19: 99-108 

Erbe C, McPherson C. 2013. Acoustic characterisation of bycatch mitigation pingers on shark control nets in Queensland, Australia. ESR 19: 109-121 

Dawson SM, Northridge S, Waples D, Read AJ. 2013. Review To ping or not to ping: the use of active acoustic devices in mitigating interactions between small cetaceans and gillnet fisheries. ESR: 19: 201-221 

Reeves RR, McClellan K, Werner TB. 2013. Review Marine mammal bycatch in gillnet and other entangling net fisheries 1990 to 2011. ESR 20: 71-97

Slooten E. 2013. Review Effectiveness of area-based management in reducing bycatch of the New Zealand dolphin. ESR 20: 121-130 

Larsen F, Krog C, Ritzau Eigaard O. 2013. Determining optimal pinger spacing for harbour porpoise bycatch mitigation. ESR 20: 147-152

Rojas-Bracho L, Reeves RR. 2013. Vaquitas and gillnets: Mexico's ultimate cetacean conservation challenge. ESR 21: 77-87 


Workshop Presentations:

Marine Mammal Bycatch in Gillnets

IWC 1990: Symposium and workshop on the mortality of cetaceans in passive fishing nets and traps
William Perrin

Global overview of marine mammal vulnerability to gillnet bycatch
Randall Reeves, Kate McClellan, and Tim Werner

Case study of harbor porpoise bycatch and pingers in the NW Atlantic
Andy Read

Gillnets: A descriptive overview and discussion of bycatch risk components
Andrew Revill and Tim Werner

FAO international guidelines on bycatch management and reduction of discards
Francis Chopin

Acoustic Deterrents

Experiences in implementing acoustic pingers in US and Canadian fisheries
Debra Palka

Acoustic deterrents in UK gillnet fisheries
Simon Northridge

Catch rates and the effectiveness of pingers in reducing Indo-Pacific bottlenose dolphin, Tursiops aduncus, incidental capture in the protective nets of KwaZulu-Natal, South Africa
Vic Peddemors

Acoustic characterization of bycatch mitigation pingers
Cristine Erbe

Review of the efficacy of acoustic deterrents for reducing marine mammal bycatch in the Baltic region, North Seas and East Africa
Per Berggren

Bycatch mitigation of harbour porpoise (Phocoena phocoena) in Dutch set net fisheries: a pilot to study the workability and efficiency of several pinger types
Marije Siemensma

To ping or not to ping? That is the question: A global review of the effectiveness of pingers in reducing gillnet bycatch of cetaceans
Steve Dawson 

Efficacy of pingers in North Pacific salmon and squid gillnet fisheries
Tomonari Akamatsu

Non-Acoustic Gear Modifications

Review of European trials of barium sulphate and metal oxide nets
Finn Larsen and Simon Northridge 

Field testing of experimental gillnets on the bycatch rates of Franciscana dolphins in Argentina
Alice Mackey and Pablo Bordino

The effects of hanging ratio on the catch of harbor porpoise and targeted finfish species
Henry Miliken and Gwynne Schnaittacher

Evaluating the impact of gillnet soak durations on bycatch of small cetaceans in the Northwest Atlantic, USA
Marjorie Rossman and Debra Palka

Mitigation strategies for mysticete gillnet entanglements in the Western North Atlantic
Scott Kraus and Scott Landry

Time-Area Closures

The impact of time-area closure on harbor porpoise bycatch reduction
Christopher Orphanides

How effective are protected areas in reducing Hector's dolphin bycatch?
Liz Slooten

Time-area closures for critically endangered species: A recipe for extinction or survival? The case of the vaquita
Lorenzo Rojas-Bracho

Impact and mitigation of Australian sea lion bycatch in the Commonwealth managed shark gillnet fishery off South Australia
Simon Goldsworthy 

Gear Switching

Switching gillnets with handlines: A strategy to reduce the bycatch of Franciscana dolphins (Pontoporia blainvillei) in Argentina
Pablo Bordino

Cod pots: An alternative fishing gear to gillnets?
Sara Königson 

Cod traps as an ecologically sound fishing gear in the German waters 
Christian Pusch

Mexican efforts to save Phocoena sinus from extinction through sustainable fisheries
Daniel Aguilar-Ramirez