Michael Tabak (Program in Ecology, Department of Zoology & Physiology, University of Wyoming, Laramie,USA) and colleagues have looked at the distribution of Brown or Norway Rats Rattus norvegicus in the Falkland Islands (Islas Malvinas)*, publishing open access in the online journal NeoBiota.  The finding that rats are likely to be able to swim farther than previously thought has implications for judging the suitability of islands cleared of rats for the reintroduction or translocation of burrowing shearwaters and petrels.

The paper’s abstract follows:

“Non-native rats (Rattus spp.) threaten native island species worldwide.  Efforts to eradicate them from islands have increased in frequency and become more ambitious in recent years. However, the long-term success of some eradication efforts has been compromised by the ability of rats, particularly Norway rats (Rattus norvegicus) which are good swimmers, to recolonize islands following eradications.  In the Falkland Islands, an archipelago in the South Atlantic Ocean, the distance of 250 m between islands (once suggested as the minimum separation distance for an effective barrier to recolonization) has shown to be in­sufficient.  Norway rats are present on about half of the 503 islands in the Falklands.  Bird diversity is lower on islands with rats and two vulnerable passerine species, Troglodytes cobbi (the only endemic Falkland Islands passerine) and Cinclodes antarcticus, have greatly reduced abundances and/or are absent on islands with rats.  We used logistic regression models to investigate the potential factors that may determine the presence of Norway rats on 158 islands in the Falkland Islands.  Our models included island area, distance to the nearest rat-infested island, island location, and the history of island use by humans as driving vari­ables.  Models best supported by data included only distance to the nearest potential source of rats and island area, but the relative magnitude of the effect of distance and area on the presence of rats varied depending on whether islands were in the eastern or western sector of the archipelago.  The human use of an island was not a significant parameter in any models.  A very large fraction (72%) of islands within 500 m of the nearest potential rat source had rats, but 97% of islands farther than 1,000 m away from potential rat sources were free of rats.”

Pycroft's Petrel: being translocated in New Zealand

Click here for a related paper on rodents in the Falkland Islands (Islas Malvinas)*.

References:

Tabak, M.A., Poncet S., Passfield, K, Carling M.D. & Martinez del Rio C 2014.  The relationship between distance and genetic similarity among invasive rat populations in the Falkland Islands.  Conservation Genetics 16: 125-135.

Tabak, M.A., Poncet, S., Passfield, K. & Martinez del Rio, C. 2015.  Modeling the distribution of Norway rats (Rattus norvegicus) on offshore islands in the Falkland Islands.  NeoBiota 24: 33-48.

John Cooper, ACAP Information Officer, 21 April 2015

*A dispute exists between the Governments of Argentina and the United Kingdom of Great Britain and Northern Ireland concerning sovereignty over the Falkland Islands (Islas Malvinas), South Georgia and the South Sandwich Islands (Islas Georgias del Sur y Islas Sandwich del Sur) and the surrounding maritime areas.

Shannon Lyday (Hawaii Pacific University, Oceanic Institute, Waimanalo, Hawaii, USA.) and colleagues write in a special issue of the Journal of Marine Systems entitled “California Current System – Predators and the Preyscape” on shearwaters (including the ACAP-candidate Pink-footed Puffinus creatopus) as indicators of fish abundance.

The paper’s abstract follows:

“Shearwaters are ideal for monitoring ocean conditions in the California Current because these predators are abundant, conspicuous, and responsive to oceanographic variability.  Herein we evaluated black-vented (Puffinus opisthomelas), Buller's (P. bulleri), flesh-footed (P. carneipes), pink-footed (P. creatopus), short-tailed (P. tenuirostris), and sooty (P. griseus) shearwaters as fishery-independent indicators of predatory or prey fish availability.  We analyzed four years (1996, 2001, 2005, 2008) of monthly (August–November) National Oceanic and Atmospheric Administration seabird surveys, and United States Geological Survey Pacific Coast Fisheries Database catch, from the California coast to 200 nm offshore.  An ordination of shearwater abundance and fish catch revealed that the shearwaters and 11 fish/squid species were significantly correlated with one or more of three principal components, which explained 86% of the variation and revealed distinct species assemblages.  We evaluated multiple linear regression models for 19 fisheries using five shearwater metrics: density, aggregation, and behavior (traveling, stationary, feeding), three oceanographic indices, and latitude.  Eight of these models had a shearwater metric as the primary predictor.  In particular, feeding black-vented shearwater abundance explained 75% of dolphinfish (Coryphaena hippurus) longline catch.  This research illustrates the utility of shearwaters as ecosystem indicators, with direct application for predicting fishery catch of commercial importance.”

Sooty Shearwater, photograph by John Graham 

Reference:

Lyday, S.E., Ballance, L.T., Field, D.B. & Hyrenbach, K.D. 2015.  Shearwaters as ecosystem indicators: towards fishery-independent metrics of fish abundance in the California Current.  Journal of Marine Systems 146: 109-120.

John Cooper, ACAP Information Officer, 20 April 2015

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