Montague Island Research Articles

Repeated Coseismic Uplift of Coastal Lagoons Above the Patton Bay Splay Fault System, Montague Island, Alaska, USA

AbstractCoseismic slip on the Patton Bay splay fault system during the 1964 Mw 9.2 Great Alaska Earthquake contributed to local tsunami generation and vertically uplifted shorelines as much as 11 m on Montague Island in Prince William Sound (PWS). Sudden uplift of 3.7–4.3 m caused coastal lagoons along the island's northwestern coast to gradually drain. The resulting change in depositional environment from marine lagoon to freshwater muskeg created a sharp, laterally continuous stratigraphic contact between silt and overlying peat. Here, we characterize the geomorphology, sedimentology, and diatom ecology across the 1964 earthquake contact and three similar prehistoric contacts within the stratigraphy of the Hidden Lagoons locality. We find that the contacts signal instances of abrupt coastal uplift that, within error, overlap the timing of independently constrained megathrust earthquakes in PWS—1964 Common Era, 760–870 yr BP, 2500–2700 yr BP, and 4120–4500 yr BP. Changes in fossil diatom assemblages across the inferred prehistoric earthquake contacts reflect ecological shifts consistent with repeated draining of a lagoon system caused by >3 m of coseismic uplift. Our observations provide evidence for four instances of combined megathrust‐splay fault ruptures that have occurred in the past ∼4,200 years in PWS. The possibility that 1964‐style combined megathrust‐splay fault ruptures may have repeated in the past warrants their consideration in future seismic and tsunami hazards assessments.

Marine reserve use by a migratory coastal shark, Carcharias taurus

Networks of small no-take marine protected areas (MPAs) are a popular approach to protect mobile marine species at key sites along their migration routes. Understanding how individuals vary in their use of these sites is needed to ensure MPA networks are optimised to offer maximum protection benefits. Using diver-led surveys, coded acoustic tags and a continental-scale collaborative network of acoustic receivers, we investigated variation in the use of three Australian MPAs by aggregating grey nurse sharks, Carcharias taurus. The Wolf Rock MPA was used year-round by C. taurus and as a gestation site, with females spending up to 254 d at the site with 2.2–3.7 year absences between residencies. In contrast, Flat Rock and Cherubs Cave-Henderson Rock MPAs were used as a transitory aggregation site with males and females occurring at the site for 30 min–59 d intervals between June–January, only. Migratory movements ranged up to 1500 km along the coastline, intersected 18 MPAs and/or recognised C. taurus aggregation sites, and connected temperate waters at Montague Island (36.25° S) with that of the southern Great Barrier Reef (23.40° S). Our study demonstrates how local receiver arrays and national collaborative acoustic telemetry networks are powerful tools to reveal use, fidelity and connectivity of MPA networks by marine migratory species. As the east Australian C. taurus population is critically endangered and at particular risk of anthropogenic threats, ongoing monitoring of the species' movement behaviour and complementary management outside protected area boundaries is warranted to assist its protection.

Using Geolocator Data to Address Changes in Migration Patterns for Black Turnstone

AbstractBlack Turnstone is an obligate Pacific coast shorebird that is included as a “Species of High Concern” in both the U.S. and Alaska Shorebird Conservation Plans. Specific migration routes for this species are not well understood, which makes its recent disappearance at a major spring stopover site, northern Montague Island in Prince William Sound, Alaska, difficult to interpret. We tracked 23 Black Turnstones between breeding and wintering areas and examined migration timing, duration, and routes used. We identified two high-use regions during migration: 1) Cook Inlet/Shelikof Strait, Alaska, and 2) the Haida Gwaii Archipelago in British Columbia/Alexander Archipelago in southeastern Alaska. This second region was also an important wintering area. We found that northbound migration was longer than southbound (the reverse of what is often observed in shorebirds) and that staging behavior was primarily seen during northbound migration. No birds were tracked to northern Montague Island, and only a few individuals stopped anywhere in Prince William Sound. Alterations in patterns of spring herring spawn in Prince William Sound may be affecting the routes and stopovers used by Black Turnstones, and birds may be wintering farther north in recent decades due to warmer winter conditions. Additionally, the increasing availability and popularity of citizen science efforts like eBird has created a mechanism for disseminating observations from less accessible parts of the Black Turnstone range, a fact which may confound our understanding of whether migration routes for this species have changed over the last 30 years.

The diet of greater crested terns off southeast Australia varies with breeding stage and sea surface temperature

Monitoring seabird diet can provide insights into marine ecosystems that are logistically difficult or costly to observe with traditional fisheries survey methods. Using digital photography, we described the diet of greater crested terns (Thalasseus bergii) breeding on Montague Island (36°15′ S, 150°13′ E), a colony located in an oceanographically dynamic region of southeast Australia. We investigated how the type and size of prey brought back to the colony changed in relation to both breeding stage and variation in local environmental conditions. 2469 prey items were identified to species or family level over 35 consecutive days of photo-sampling in 2018. Australian anchovy (Engraulis australis), a surface-schooling clupeid fish, was the most abundant prey returned to the colony during all breeding stages (84.5%). The proportion of anchovy increased from 77.0% when birds were provisioning their adult partners during incubation, to 92.4% when they were provisioning chicks, suggesting selective foraging behaviour on this energy-rich species to facilitate rapid chick growth. Anchovy size was significantly larger during incubation (91.1 ± 14.9 mm), smaller during early chick provisioning (71.8 ± 11.0 mm), and increased slightly during mid provisioning (79.6 ± 11.9 mm), indicating adaptive prey selection that is matched to the physical requirements of different breeding stages. The proportion of anchovy prey was also influenced by sea surface temperature (SST), with anchovy becoming more dominant with increasing local SSTs, up to ~ 17.5 °C. This study gives new insight into the types of prey that are seasonally available to predators in this region. The strong specialisation by greater crested terns for one energy-rich species of schooling fish (anchovy) suggests that variation in the size and composition of their prey may serve as an indicator of change in the pelagic ecosystem off southeast Australia.

High prevalence of Salmonella and IMP-4-producing Enterobacteriaceae in the silver gull on Five Islands, Australia.

ObjectivesThe objective of this study was to investigate the silver gull as an indicator of environmental contamination by salmonellae and carbapenemase-producing Enterobacteriaceae (CPE) in south-east Australia.MethodsA total of 504 cloacal samples were collected from gull chicks at three nesting colonies in New South Wales, Australia [White Bay (n = 144), Five Islands (n = 200) and Montague Island (n = 160)] and were examined for salmonellae and CPE. Isolates were tested for carbapenemase genes and susceptibility to 14 antibiotics. Clonality was determined by PFGE and MLST. Genetic context and conjugative transfer of the carbapenemase gene were determined.ResultsA total of 120 CPE of 10 species, mainly Escherichia coli (n = 85), carrying the gene blaIMP-4, blaIMP-38 or blaIMP-26 were obtained from 80 (40%) gulls from Five Islands. Thirty percent of birds from this colony were colonized by salmonellae. Most isolates contained the gene within a class 1 integron showing a blaIMP-4-qacG-aacA4-catB3 array. The blaIMP gene was carried by conjugative plasmids of variable sizes (80–400 kb) and diverse replicons, including HI2-N (n = 30), HI2 (11), A/C (17), A/C-Y (2), L/M (5), I1 (1) and non-typeable (6). Despite the overall high genetic variability, common clones and plasmid types were shared by different birds and bacterial isolates, respectively.ConclusionsOur data demonstrate a large-scale transmission of carbapenemase-producing bacteria into wildlife, likely as a result of the feeding habits of the birds at a local waste depot. The isolates from gulls showed significant similarities with clinical isolates from Australia, suggesting the human origin of the isolates. The sources of CPE for gulls on Five Islands should be explored and proper measures applied to stop the transmission into the environment.

Focused rock uplift above the subduction décollement at Montague and Hinchinbrook Islands, Prince William Sound, Alaska

Megathrust splay fault systems in accretionary prisms have been identified as conduits for long-term plate motion and significant coseismic slip during subduction earthquakes. These fault systems are important because of their role in generating tsunamis, but rarely are emergent above sea level where their long-term (million year) history can be studied. We present 32 apatite (U-Th)/He (AHe) and 27 apatite fission-track (AFT) ages from rocks along an emergent megathrust splay fault system in the Prince William Sound region of Alaska above the shallowly subducting Yakutat microplate. The data show focused exhumation along the Patton Bay megathrust splay fault system since 3–2 Ma. Most AHe ages are younger than 5 Ma; some are as young as 1.1 Ma. AHe ages are youngest at the southwest end of Montague Island, where maximum fault displacement occurred on the Hanning Bay and Patton Bay faults and the highest shoreline uplift occurred during the 1964 earthquake. AFT ages range from ca. 20 to 5 Ma. Age changes across the Montague Strait fault, north of Montague Island, suggest that this fault may be a major structural boundary that acts as backstop to deformation and may be the westward mechanical continuation of the Bagley fault system backstop in the Saint Elias orogen. The regional pattern of ages and corresponding cooling and exhumation rates indicate that the Montague and Hinchinbrook Island splay faults, though separated by only a few kilometers, accommodate kilometer-scale exhumation above a shallowly subducting plate at million year time scales. This long-term pattern of exhumation also reflects short-term seismogenic uplift patterns formed during the 1964 earthquake. The increase in rock uplift and exhumation rate ca. 3–2 Ma is coincident with increased glacial erosion that, in combination with the fault-bounded, narrow width of the islands, has limited topographic development. Increased exhumation starting ca. 3–2 Ma is interpreted to be due to rock uplift caused by increased underplating of sediments derived from the Saint Elias orogen, which was being rapidly eroded at that time.

First photographic records of the giant manta ray Manta birostris off eastern Australia.

We present the first photographic evidence of the presence of the giant manta ray Manta birostris in east Australian waters. Two individuals were photographed off Montague Island in New South Wales and off the north east coast of Tasmania, during summer 2012 and 2014, respectively. These sightings confirm previous unverified reports on the species occurrence and extend the known distribution range of M. birostris to 40°S. We discuss these findings in the context of the species’ migratory behaviour, the regional oceanography along the south east Australian coastline and local productivity events.

Fur seal activity moderates the effects of an Australian marine sanctuary on temperate reef fish

Offshore islands are often preferentially selected for marine sanctuaries (no take areas) over inshore reefs on populated coasts because they support relatively unique marine communities and critical habitat for protected marine wildlife and are often less accessible to people. To evaluate whether marine sanctuaries around an offshore island with a large fur seal colony performed differently to inshore areas, we compared fish assemblages at 36 reef sites within marine sanctuaries and fished areas around an offshore Island and within inshore areas of the Batemans Marine Park in temperate southeastern Australia. In each site, we quantified fish assemblage structure using 3–4 replicate baited remote underwater video deployments. We also evaluated the role of fur seal activity, sea surface temperature and wave exposure in structuring fish assemblages on reefs inside and outside marine sanctuaries. Of these variables, only fur seal activity on shallow island reefs (∼10m deep) was significantly related to fish assemblage structure with a negative relationship to fish richness and abundance. The fish assemblages in marine sanctuaries differed significantly from fished areas on deep reefs around Montague Island (30–40m deep) and on shallow inshore reefs (∼10m deep), with 119% and 45% more fish and 49% and 19% more species of fishes in marine sanctuaries in the two areas, respectively. There were also significantly more kyphosids, labrids, southern maori wrasse (Ophthalmolepis lineolatus) and silver sweep (Scorpis lineolata) in marine sanctuaries than in fished areas on deep reefs around Montague Island. Although there was, on average, 34% more fish on shallow reefs inside than outside marine sanctuaries around Montague Island, there were no significant differences in fish assemblages when the influence of fur seal activity was taken into account. Given that fur seals numbers are increasing and they eat reef fishes, marine sanctuaries on shallow reefs adjacent to seal colonies may not achieve some of the positive benefits associated with increased fish biomass (e.g. increased kelp cover) to same level as sanctuaries more distantly located. We suggest, therefore, that careful consideration of long-term conservation goals (e.g. conservation of fur seals or local enhancement of fish diversity) is needed before preferentially locating marine sanctuaries adjacent to fur seal colonies.

Focused exhumation along megathrust splay faults in Prince William Sound, Alaska

Megathrust splay faults are a common feature of accretionary prisms and can be important for generating tsunamis during some subduction zone earthquakes. Here we provide new evidence from Alaska that megathrust splay faults have been conduits for focused exhumation in the last 5 Ma. In most of central Prince William Sound, published and new low-temperature thermochronology data indicate little to no permanent rock uplift over tens of thousands of earthquake cycles. However, in southern Prince William Sound on Montague Island, apatite (U–Th)/He ages are as young as 1.1 Ma indicating focused and rapid rock uplift. Montague Island lies in the hanging wall of the Patton Bay megathrust splay fault system, which ruptured during the 1964 M9.2 earthquake and produced ∼9 m of vertical uplift. Recent geochronology and thermochronology studies show rapid exhumation within the last 5 Ma in a pattern similar to the coseismic uplift in the 1964 earthquake, demonstrating that splay fault slip is a long term (3–5 my) phenomena. The region of slower exhumation correlates with rocks that are older and metamorphosed and constitute a mechanically strong backstop. The region of rapid exhumation consists of much younger and weakly metamorphosed rocks, which we infer are mechanically weak. The region of rapid exhumation is separated from the region of slow exhumation by the newly identified Montague Strait Fault. New sparker high-resolution bathymetry, seismic reflection profiles, and a 2012 Mw4.8 earthquake show this feature as a 75-km-long high-angle active normal fault. There are numerous smaller active normal(?) faults in the region between the Montague Strait Fault and the splay faults. We interpret this hanging wall extension as developing between the rapidly uplifting sliver of younger and weaker rocks on Montague Island from the essentially fixed region to the north. Deep seismic reflection profiles show the splay faults root into the subduction megathrust where there is probable underplating. Thus the exhumation and extension in the hanging wall are likely driven by underplating along the megathrust décollement, thickening in the overriding plate and a change in rheology at the Montague Strait Fault to form a structural backstop. A comparison with other megathrust splay faults around the world shows they have significant variability in their characteristics, and the conditions for their formation are not particularly unique.

Megathrust splay faults at the focus of the Prince William Sound asperity, Alaska

AbstractHigh‐resolution sparker and crustal‐scale air gun seismic reflection data, coupled with repeat bathymetric surveys, document a region of repeated coseismic uplift on the portion of the Alaska subduction zone that ruptured in 1964. This area defines the western limit of Prince William Sound. Differencing of vintage and modern bathymetric surveys shows that the region of greatest uplift related to the 1964 Great Alaska earthquake was focused along a series of subparallel faults beneath Prince William Sound and the adjacent Gulf of Alaska shelf. Bathymetric differencing indicates that 12 m of coseismic uplift occurred along two faults that reached the seafloor as submarine terraces on the Cape Cleare bank southwest of Montague Island. Sparker seismic reflection data provide cumulative Holocene slip estimates as high as 9 mm/yr along a series of splay thrust faults within both the inner wedge and transition zone of the accretionary prism. Crustal seismic data show that these megathrust splay faults root separately into the subduction zone décollement. Splay fault divergence from this megathrust correlates with changes in midcrustal seismic velocity and magnetic susceptibility values, best explained by duplexing of the subducted Yakutat terrane rocks above Pacific plate rocks along the trailing edge of the Yakutat terrane. Although each splay fault is capable of independent motion, we conclude that the identified splay faults rupture in a similar pattern during successive megathrust earthquakes and that the region of greatest seismic coupling has remained consistent throughout the Holocene.

Geomorphology of a Recurring Tidal Sandbar in the estuary of the Colorado River, Mexico: Implications for restoration

An obstructive tidal sandbar forms in the estuary of the Colorado River, Mexico, during periods of low fluvial discharge. The sandbar typically develops at a bedload convergence zone centered approximately 30km landward from Montague Island near the river's mouth. The estuary provides important spawning habitat for the endangered totoaba (Totoaba macdonaldi) and commercially exploited Gulf corvina (Cynoscion othonopterus), as well as habitat for larval shrimp, all of which are impacted by reduced freshwater/sea water mixing when the sandbar is present.Sequential satellite images, aerial photographs, overflights, and ground observations were used to document the geomorphology of the tidal sandbar and its formation, removal, and subsequent reappearance in response to long-term variations in fluvial flow following completion of Glen Canyon Dam in 1964. Evidence for the formation of the sandbar during low-discharge periods prior to anthropogenic manipulation of the river's flow was also examined.Water data sensors were installed upstream from the current sandbar to monitor the frequency of tidal overflow and document the effect of tides on salinity. Topographic surveys of the sandbar were completed both before and after the 2010 Mw 7.2 El Mayor-Cucapah Earthquake which caused subsidence of lands immediately east of the sandbar's crest.Utilizing topographic data and knowledge of the sandbar's geomorphologic and sedimentary history, we designed and installed a system of dredged pilot channels to improve connectivity between the upper and lower estuary by facilitating tidal and fluvial flow across the barrier. The effectiveness of the pilot channels is currently under evaluation. If the pilot channels fail to establish the desired level of connectivity, installation and maintenance of a more substantial dredged channel may be necessary to meet restoration objectives.

Valuing the wealth of restorative activity and using it as a source of inspiration

This issue of EMR contains an unusually high number of articles relating to fauna and habitat management, including both research and on-ground projects. This issue’s two features, for example – one on improving fire regimes in the Kimberley, Western Australia (Legge et al., this issue), and the other on removing cats from Christmas Island (Hilmer et al.) – both represent cutting edge initiatives to improve habitats for native species, particularly threatened species. These are impressive initiatives that go beyond current best practice, breaking new ground to inspire others elsewhere to adapt the initiatives for their own areas. Also among the longer and shorter research reports in this issue are articles on the eradication of the House Mouse from Montague Island, WA (Cory et al. this issue); trials to improve reptile environments in the agricultural landscape by removing tree regrowth around rocky outcrops (Pike et al. this issue), and assessment of the longevity of habitat log piles (Grigg, this issue). All these seek to trial (or add insight into) possible solutions to current environmental challenges. While there are many papers on fauna and habitat topics in this issue, vegetation matters are not neglected. Longer articles include a timely review of the range of values of the networks of travelling stock routes and reserves in NSW and Queensland (Lentini et al. this issue) and a method of assessing the relative conservation values of wetlands in the Murray-Darling Basin to maximise the conservation management effectiveness of environmental water use (Peake et al. this issue). Shorter reports continue on the theme of vegetation assessment (Briggs et al., Kelly et al. and Lentini et al. this issue), and there are also a number of notes relating to revegetation techniques (So et al., Ruthroff et al. and Grose this issue), all of which are highly relevant to improving on-ground restoration outcomes. Indeed, the breadth of articles shows that there is a wealth of restoration management activity going on in Australia involving both plant and animal habitats and that managers are recognising the need to draw upon research expertise to enhance success. Researchers are also drawing increasingly on the special insights of managers. This two-way process is no better reflected than in this issue’s guest editorial by David Freudenberger and team from the practitioner organisation Greening Australia, who outline their initiative to become involved in the Ecological Society of Australia’s (ESA) 2010 conference. Among other things this involved the team pitching their own presentations to appeal to researchers interested in applied science and seeking to involve in symposia, researchers whose work would appeal to managers. The point of their article is to encourage other practitioner groups to become involved in this and other such conferences, to ‘collaborate with the great talent of ecological researchers in Australia’. While we cannot be blind to the increasing alienation and decline of natural environments across the globe, we need to be encouraged by the wealth of environmental repair work going on across the country and the rest of the world. If this number of projects can be represented in just one small issue of EMR, it stands to reason that there are many more projects out there in various stages of gestation, development and completion. As ecologists, policy makers and practitioners, we are doing our bit, but thankfully there are also many projects being undertaken in the related field of sustainability science and practice that have potential to address some of the causes of ecosystem decline, projects which can further inspire cross-disciplinary initiatives. (Please note that EMR is open to consider papers on any such work.) Readers may have missed the project summaries in the last issue and may be wondering whether EMR has lost an important element? The answer is no – EMR is developing a web-based project summaries facility, which will be similar in scope to our traditional paper project summaries but they will be much more readable, permanently archived and fully searchable and illustrated with coloured photos and maps etc. Many summaries are being uploaded onto the new website as I write, and when it is up and running, we will promote its launch through the ESA and EMR’s affiliate practitioner organisations. We hope that readers, once inspired by the summaries they read, will give some thought to whether one or more of their own projects, however small or incomplete, might suit a summary. In the meantime, please email your ideas for project summaries to me at emreditor@ecolsoc.org.au.

Eradication of the House Mouse (Mus musculus) from Montague Island, New South Wales, Australia

Summary Of all the introduced mammalian pests, rodents are the most common invaders of islands and have triggered numerous extinctions around the globe. They have a short gestation period and large litter size, giving them the ability to colonise new areas rapidly. The same biological traits make them difficult to eradicate. Although the biodiversity benefits of removing exotic rodents from islands are increasingly being recognised, there are few published analyses of eradication attempts that critically evaluate eradication tools. This study examined the response of House Mouse (Mus musculus) populations to an eradication operation on Montague Island, Australia. While the specific impacts of mice have not been studied on this particular island, elsewhere they have been shown to have negative impacts on a range of species including plants, invertebrates, lizards and seabirds. On Montague Island, mouse abundance across different habitats was examined using mark–recapture data collected before and after the deployment of brodifacoum baits. Data obtained before baiting showed significantly lower numbers of mice in sites dominated by exotic grass compared with those dominated by native vegetation. Mouse numbers overall were declining during winter and the population was not breeding, making this an optimal time to undertake the eradication. Trapping immediately after the initial bait drop failed to capture any survivors, and no individuals have been detected during the 3 years since the deployment of baits. This study demonstrated that both small and large baits (0.6 and 2 g pellets) were effective in eradicating the House Mouse from Montague Island. While present, mice were probably slowing the re-establishment of native vegetation by grazing seedlings and consuming seeds. With this pest now gone, the process of natural regeneration is expected to accelerate. The eradication of the House Mouse from Montague is likely to have other positive effects on the island’s biodiversity. The operation itself contributed to enhancing local capacity to eradicate exotic rodents from larger or more complex islands.

Improving Oil Spill Environmental Sensitivity Maps with ShoreZone Imagery, Examples from Prince William Sound

Example 1: Northern Port Chalmers, Montague Island Environmental Sensitivity Index (ESI) mapping proposes to provide accurate representation of an area’s shoreline categorized as to shoreline type on a scale of 1 to 10 determined by sensitivity to spilled oil. Originally, field work utilized the hand-drawing of categories onto USGS topographic maps while seated in an aircraft flying the coastline. ESI categorization could only be verified by photographs taken at the time and by intermittent ground truthing. ESI maps could not be verified by others, especially if remote coastline was involved. Today large sections of the Alaskan coastline have been flown by the ShoreZone program which has captured high-resolution still photographs (able to resolve shoreline features of ~0.3 m and less) and lower resolution continuous video imaging taken from a lowand slow-flying helicopter. Both video and still photographs are readily available at (http://alaskafisheries.noaa.gov/habitat/shorezone/szintro.htm) enabling a desk-side review of any specific location at any time. A voice-over recorded during the survey is also available, but not online. Prince William Sound (PWS) has been ESI-categorized several times, most recently in 1999 (2007 digital rerelease). I compared several parts of the current PWS ESI shoreline with ShoreZone imagery using the ESI maps in ESRI ArcMap and supported by GoogleEarth. Multiple examples find that the current ESI maps commonly do not take into account features less than ~100 m in length (thereby omitting many pocket gravel beaches and rock platforms), may overlook features (e.g. large tidal flats as in the Port Chalmers and Lower Passage areas), have the wrong location for divisional boundaries between shoreline types, are inconsistent within a shoreline type category (particularly sheltered rubble slopes (8D)) and, while getting the overall features generally correct, are commonly in error at many specific locations. A thorough review of current ESI shoreline maps using the readily available ShoreZone images will improve both the accuracy and resolution of these maps, not only in Prince William Sound but in other areas where ShoreZone images are available.

Marmota Caligata (Rodentia: Sciuridae)

Abstract Marmota caligata (Eschscholtz, 1829), a large ground squirrel commonly called the hoary marmot, is 1 of 15 species of extant marmots. It is distributed in western North America from Alaska and Canada south to Washington and Montana and is found at elevations ranging from sea level to 2,500 m. M. caligata prefers alpine and subalpine boulder piles and talus slopes surrounded by meadows. The species is listed as “Least Concern” by the International Union for Conservation of Nature and Natural Resources, although populations of Montague Island and Glacier Bay are of conservation concern by the State of Alaska.

Report on Montagu Island (United Kingdom)

Report on Montagu Island (United Kingdom)

Long-range migration of a chinstrap penguin from Bouvetøya to Montagu Island, South Sandwich Islands

AbstractWe describe a long-range migration of a pre-moulting adult chinstrap penguin from Bouvetøya, a small relatively recently established colony, to the South Sandwich Islands, where large, established colonies of this species reside. The trip lasted around three weeks, covered ∼3600 km, and the time of arrival was consistent with the annual moult. The bird did not travel along the shortest path or along a constant bearing, but instead followed what appeared to be a series of two or three rhumb lines of constant bearing. Small southward and northward deviations from the general path were consistent with local water currents. Travel speeds were high during daylight but decreased at night, suggesting that resting or opportunistic feeding occurred preferentially at night. While long-range winter migrations of chinstraps to feeding areas in the vicinity of distant colonies have been previously described, this is the first observation of such a trip during the period between breeding and moulting, and the first record of an individual actually arriving at one of these distant colonies. This has implications for understanding population structure and management of this important Southern Ocean predator.

A viscoelastic and afterslip postseismic deformation model for the 1964 Alaska earthquake

We developed a 3‐D viscoelastic model, in concert with an afterslip model, to describe the postseismic deformation following the 1964 Alaska earthquake. Our model incorporates a realistic geometry including an elastic slab with very low dip angle. These geometric factors are important and require a reanalysis of the 1964 coseismic model. Our coseismic model differs from previous models in that the Montague Island splay fault extends farther along the Kenai Peninsula coast, and as a result, slip on the megathrust in that region is smaller. We computed postseismic deformation models using a range of mantle viscosities with Maxwell relaxation time τ of 1 to 50 years, with a best estimate of 20 years. The viscoelastic model explains most of the trenchward motion observed in the present velocity field but has little impact on cumulative 1965 to present uplifts. After removing the viscoelastic response, the largest residual cumulative uplifts were located downdip from areas of largest coseismic slip area, and we explain them using an afterslip model, constrained in space by the observed cumulative postseismic uplifts and in time by tide gauge records. No single mechanism can explain both the 30 years of cumulative uplift and the present velocities, but a combination of viscoelastic relaxation, afterslip, interseismic elastic deformation, and motion of southern Alaska relative to North America explains the first‐order features of the observations. Forty years after the earthquake, the present‐day velocities contain a significant component of postseismic deformation, so very long lived postseismic deformation plays an important role in the subduction zone earthquake cycle for great earthquakes.

Do Tour Boats Affect Fur Seals at Montague Island, New South Wales?

Interactions between fur seals (Arctocephalus pusillus doriferus and A. forsteri) and tour boats at Montague Island were investigated between November 1997 and November 1998. The fur seals were in four haul-out sites, which are referred to here as colonies. The study was instigated by the management requirement of the National Parks and Wildlife Service of New South Wales to determine effects of disturbance from tour boats on the fur seal colonies. At each of 84 inspections, distance between the boat and the colony was measured and seal behavior (or response) was recorded 11 times at 15-second intervals as the boat moved toward the seals. This period of 2.5 minutes was approximately the time tour boats stayed at a colony. Behavior of the fur seals ashore was recorded in four categories of increasing disturbance from "Resting" to "Many moving." From analyses using multinomial models, the probability of observing a given response by the fur seals and the pattern of the responses as a function of distance from the colony were both influenced by the colony under observation. In general, fur seals' responses were significantly correlated with distance between the study boat and the colony, and with the size of the colony (i.e., number of fur seals visible ashore). In all cases, the probability of the colony remaining in the "Resting" category decreased as the distance between the colony and the study boat decreased. Similarly the probability of the colony showing the maximum response ("Many moving") increased as the distance decreased. The probability of New Zealand fur seals "Resting" was higher than for Australian fur seals. Tour boats approaching the colonies had a relatively small effect on the fur seals; few or none of them ran to the sea. Based on results from this study, we recommended that the minimum approach distance of tour boats to the fur seal colonies at Montague Island should be 40 m; other recommendations involved how tour boats approach the fur seal colonies. The former has been gazetted as a government regulation and the other recommendations have been incorporated into the license conditions for the tour boats operators.

Volcanic features and the hydrological setting of Southern Thule, South Sandwich Islands

AbstractThis paper provides new observations of volcanic features and hydrological characteristics in and around Southern Thule, the southernmost group of islands in the South Sandwich Islands, including the first high-resolution bathymetric image of the Douglas Strait caldera. The South Sandwich Islands are the summits of several very large subduction-related volcanoes constructed at the eastern boundary of the Scotia Sea. Observations of the islands are scarce owing to their remote location and they are only rarely visited, yet the area is an active volcanic arc that is rapidly changing as a result of eruptions, including one (on Montagu Island) that has been ongoing for six years and is creating new land. The three islands that make up Southern Thule are morphologically different, and they illustrate different stages in the construction and evolution of islands in the South Sandwich group. We present the results of an acoustic and hydrographic survey that resulted in the first high-resolution, multibeam ‘swath’ image of the submarine Douglas Strait caldera. The results confirm the presence of a large sediment mound (c. 1000 m3 in volume) on the floor of the Douglas Strait caldera related to a flank collapse of Thule Island. The image also shows an extensive arcuate fault structure, interpreted as evidence that the caldera is nested, and its geomorphological freshness suggests that it is a very young feature that formed conceivably in the last few decades or centuries. The bathymetric image also reveals at least three cone- or mound-like structures within the caldera that may relate to renewed post-caldera volcanism (as pyroclastic cones and/or pillow mounds). Recently formed cones and faults associated with caldera rims are often associated with hydrothermal activity. However, temperature and salinity data collected within the caldera do not yet show any evidence of hydrothermal venting. The ocean surrounding Southern Thule has a prominent surface layer of low salinity water that is probably caused by a high meltwater flux derived from ice caps on the islands. This flux may have been enhanced by the recent warming trend observed in the Antarctic Peninsula, although volcano-related geothermal melting in the ice-filled Thule Island caldera may also contribute to the meltwater flux.