A workshop held earlier this year by the American Bird Conservancy and BirdLife International in the USA discussed methods of reducing non-target bycatch in gill nets.  “The main objectives of the workshop were to identify possible gillnet bycatch reduction methods that could be effective across taxonomic groups (seabirds, sea turtles, and sea mammals) and produce specific projects and plans for testing those methods.”

Shearwaters, like this Short-tailed, are at risk to drowning in gill nets, photograph by Kirk Zufelt

The report’s Executive Summary follows:

“The focus of the workshop was on technical methods of bycatch reduction of sea turtles, seabirds, and sea mammals in gillnets.  The workshop was carried out 21-23 January 2015 with 35 participants from seven countries and 17 organizations, representing collective expertise from fishermen, academia, government employees, and conservation Non-Governmental Organizations (NGOs).  The workshop objectives were to identify proposed gillnet bycatch mitigation methods, develop plans for trialing those methods, estimate the costs of trials, and identify teams who would work to carry out the trials.  The workshop began with a series of presentations to provide background for the discussions to follow.   This included presentations on where gillnet bycatch is known to occur; on the factors that influence bycatch probability; on the sensory abilities of the bycatch species to detect various potential mitigation methods; and on the results of previous workshops on gillnet bycatch reduction. Presentations also described bycatch reduction methods now being trialed, and gave a case study of successful technical mitigation for seabirds in the US Pacific Northwest.  Workshop subgroups proposed bycatch reduction methods that can be placed into two categories:

• Active methods, including net lights and pingers in various configurations.
• Passive methods, such as high-contrast panels placed within nets, streamers, or colored nets or portions of nets.

To encourage industry support for such measures, a key aspect of all proposed methods was that they should maintain the level of target catch, to the extent possible, while reducing bycatch.  Based on the proposed mitigation methods, workshop subgroups proposed a set of trial projects. For each project or set of projects, a region was identified where the project could be carried out, ensuring:

• Adequate bycatch levels to detect the efficacy of mitigation measures.
• The necessary infrastructure and partners present to carry out trials.
• Representation across the taxa groups.
• Good prospects of financial support for the project.

Key actors and leaders were identified for each project.  The proposed projects fell into five regional groupings:

• North Pacific: With a focus on seabird bycatch (particularly alcids) in salmon driftnets, trials of net striping, pingers, high-visibility sections, and dropped headlines were proposed. A specific North Pacific salmon driftnet workshop was suggested, to examine common approaches to bycatch mitigation.
• Northwest Atlantic: The workshop proposed trials of net lights, double-weighted lead lines, colored nets, and high-visibility sections in Newfoundland gillnet fisheries, where there are already strong connections between fishermen, academics, NGOs and management authorities.  The focus here would be on seabirds, porpoises, and pinnipeds. Sea turtle-focused projects testing low-profile nets were proposed off the US east coast.
• Northeast Atlantic: The group recommended trials of net lights and high-visibility panels placed in nets on the south coast of England to look at effects on cetaceans and proposed trials of the same methods in the Baltic Sea, focusing on sea duck bycatch (ongoing work by BirdLife International (BLI) in Lithuania, potentially some new work in Latvia or Germany).
• South America: In Chile, where seabird (penguins and shearwaters in particular), sea turtle, and cetacean bycatch is of particular concern, the group proposed the continuation of a project on high-visibility net panels being led by the Albatross Task Force (ATF).  In Peru, the continuation of mitigation projects testing net lights and subsurface nets for reduction of bycatch of sea turtles, seabirds, and sea mammals, led by ProDelphinus working with various partners, was proposed. The workshop groups noted that southern Brazil is an important to place to link with existing projects and partners to improve understanding of the visual capacities of target and bycatch species. In addition, a laboratory project on seabird underwater hearing capacity was proposed, but not at a specific site.  The tests would need to be carried out at a research facility with access to captive live birds and large seawater tanks, such as the US Geological Surveys (USGS) Patuxent Wildlife Research Center (Maryland, USA) or one of the large aquariums.  The crucial next steps following the workshop are to push forward the proposed projects, seeking financing and support of various partners and stakeholder groups.  In addition, it is clearly necessary to gain a deeper understanding of how marine mammals, seabirds, and sea turtles interact with gillnets.  Although this can be difficult because of the nature of the fisheries, it will be crucial in informing the design of mitigation measures. Participants agreed that information sharing on best practice and lessons learned across projects is [are] very important, something the workshop organizers will seek to facilitate.”

With thanks to Barry Baker, Rory Crawford and David Wiedenfeld for information.

Reference:

Wiedenfeld, D.A., Crawford, R. & Pott, C.M. 2015.  Results of a Workshop on Reduction of Bycatch of Seabirds, Sea Turtles, and Sea Mammals in Gillnets.  National Conservation Training Center Shepherdstown, West Virginia, USA, 21-23 January 2015.  American Bird Conservancy & BirdLife International.  pp. 36.

John Cooper, ACAP Information Officer, 19 April 2015

A Northern Giant Petrel Macronectes halli was observed feeding from tethered bait deployed to attract Great White Sharks Carcharodon carcharias to a tourist vessel near Dyer Island off South Africa’s southern coast on 8 April.  It sustained two wounds to its left side when a Great White approached the bait.  The bird, a juvenile by its all-dark plumage, was then captured in a scoop net and taken to the African Penguin and Seabird Sanctuary’s newly opened rehabilitation centre in Gansbaai (click here).  The sanctuary is a project of the Dyer Island Conservation Trust.

Following three stitches by a vet the bird is now doing (and eating) well in temporary captivity.

UPDATE: The bird was released to sea on 15 May at a mass of 4.6 kg, having gained 1.05 kg in captivity.

The shark approaches the bait - and the giant petrel, photograph by Jeremy Miller

The wounded giant petrel in captivity, photographs courtesy of the African Penguin and Seabird Sanctuary 

Great White Sharks are infrequent predators of seabirds around Dyer Island, with only a couple of attacks reported on African Penguins Spheniscus demersus and Kelp Gulls Larus dominicanus in one study, so it seems likely the shark in this instance was going for the bait, rather than for the bird.  Two other studies have reported penguins and gulls as prey of Great White Sharks in South African waters.

Click here to watch a video of Tiger Sharks C. taurus attacking fledgling Laysan Albatrosses Phoebastria immutabilis.

With thanks to Wilfred Chivell for information.

Selected Literature:

Bass, A.J., D’aurbrey, J.D. & Kitnasamy, N. 1975.  Sharks of the east coast of southern Africa.  The families Odontaspididae. Scapanorhynchidae, Isuridae. Cetorhinidae. Alopiidae and Rhiniodontidae.  Investigational Reports of the Oceanographic Research Institute 39: 1-102.

Johnson, R. L., Venter, A., Bester, M.N. & Oosthuizen, W.H. 2006.  Seabird predation by white shark Carcharodon carcharias and Cape fur seal Arctocephalus pusillus pusillusat Dyer Island.  South African Journal of Wildlife Research 36: 23-32.

Randall, B.M., Randell, R.M. & Compagno, L.J.V. 1988.  Injuries to jackass penguins (Spheniscus demersus): evidence of shark involvement.  Journal of Zoology (London) 214: 589-599.

John Cooper, ACAP Information Officer, 18 April 2015, updated 14 July 2015

Jan van Franeker (IMARES, Wageningen-UR, AD Den Burg (Texel), Netherlands) and Kara Law have published open access in the journal Environmental Pollution on ingestion of plastic by the Arctic or Northern Fulmar Fulmarus glacialis.

The paper’s abstract follows:

“Fulmars are effective biological indicators of the abundance of floating plastic marine debris. Long-term data reveal high plastic abundance in the southern North Sea, gradually decreasing to the north at increasing distance from population centres, with lowest levels in high-arctic waters.  Since the 1980s, pre-production plastic pellets in North Sea fulmars have decreased by ~75%, while user plastics varied without a strong overall change.  Similar trends were found in net-collected floating plastic debris in the North Atlantic subtropical gyre, with a ~75% decrease in plastic pellets and no obvious trend in user plastic.  The decreases in pellets suggest that changes in litter input are rapidly visible in the environment not only close to presumed sources, but also far from land.  Floating plastic debris is rapidly “lost” from the ocean surface to other as-yet undetermined sinks in the marine environment.”

An Arctic Fulmar corpse entangled with a balloon

For three earlier papers on Arctic Fulmars ingesting plastic by Jan van Franeker click here, here and here.

Read more of Jan’s work on plastic ingestion by seabirds here.

Reference:

van Franeker, J.A. & Law, K.L. 2015.  Seabirds, gyres and global trends in plastic pollution.  Environmental Pollution 203: 89-96.

John Cooper, ACAP Information Officer, 17 April 2015

Stephen Totterman (Empire Vale, New South Wales, Australia) has published early on-line in the journal Marine Ornithology on sexing Wedge-tailed Shearwaters Puffinus pacificus.

The paper’s abstract follows:

“Identifying female and male birds can be very helpful in field studies.  However, sexual differences in size and plumage are subtle in most petrels.  Four field methods were compared for sexing breeding Wedge-tailed Shearwaters Puffinus pacificus on Muttonbird Island, New South Wales, Australia: cloaca inspection, biometrics, acoustics and playback-response. Accuracy was evaluated against molecular tests.  A biometric discriminant function combining bill depth and total head length sexed 81% of birds (79 of 98) correctly.  Males averaged 3% larger than females, with overlapping size ranges.  Sexual differences in cloacal size were not always obvious because female cloacae gradually relapse after laying and males struggling in the hand can present extruded cloacae.  Cloacal sexing was 86% correct (93 of 108 birds).  Withinpair comparisons of biometrics and cloacal size increased sex classification accuracy for twice the effort (two birds evaluated rather than one).  An acoustic discriminant function combining fundamental frequency and note length from burrow call recordings sexed 97% of birds (102 of 105) correctly.  A novel playback-response test was efficient and sexed 94% of birds (47 of 50) correctly.”

Wedge-tailed Shearwaters

Reference:

Totterman, S.L. 2015.  A comparative evaluation of four field methods for sexing Wedge-tailed Shearwaters Puffinus pacificus.  Marine Ornithology 43: 83-93.

John Cooper, ACAP Information Officer, 16 April 2015