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Mesopelagic fish (meso-fish) are central species within the Southern Ocean (SO). However, their ecosystem role and adaptive capacity to climate change are rarely integrated into marine protected area (MPAs) assessments. This is a pity given their importance as crucial prey and predators in food webs, coupled with the impacts of climate change. Here, we estimate the habitat distribution of nine meso-fish using an ensemble model approach (MAXENT, random forest, and boosted regression tree). Four climate model simulations were used to project their distribution under two representative concentration pathways (RCP4.5 and RCP8.5) for short-term (2006–2055) and long-term (2050–2099) periods. In addition, we assess the ecological representativeness of established and proposed MPAs under climate change scenarios using meso-fish as indicator species. Our models show that all species shift poleward in the future. Lanternfishes (family Myctophidae) are predicted to migrate poleward more than other families (Paralepididae, Nototheniidae, Bathylagidae, and Gonostomatidae). In comparison, lanternfishes were projected to increase habitat area in the eastern SO but lose area in the western SO; the opposite was projected for species in other families. Important areas (IAs) of meso-fish are mainly distributed near the Antarctic Peninsula and East Antarctica. Proposed MPAs cover 23% of IAs at present and 38% of IAs in the future (RCP8.5, long-term future). Many IAs of meso-fish still need to be included in MPA proposals, such as the Prydz Bay and the seas around the Antarctic Peninsula. Our results provide a framework for designing new MPAs incorporating climate change adaptation strategies for MPA management.

Southern Ocean ecosystems are under pressure from resource exploitation and climate change1,2. Mitigation requires the identification and protection of Areas of Ecological Significance (AESs), which have so far not been determined at the ocean-basin scale. Here, using assemblage-level tracking of marine predators, we identify AESs for this globally important region and assess current threats and protection levels. Integration of more than 4,000 tracks from 17 bird and mammal species reveals AESs around sub-Antarctic islands in the Atlantic and Indian Oceans and over the Antarctic continental shelf. Fishing pressure is disproportionately concentrated inside AESs, and climate change over the next century is predicted to impose pressure on these areas, particularly around the Antarctic continent. At present, 7.1% of the ocean south of 40°S is under formal protection, including 29% of the total AESs. The establishment and regular revision of networks of protection that encompass AESs are needed to provide long-term mitigation of growing pressures on Southern Ocean ecosystems.

The Southern Ocean is a critical component of the global climate system and an important ecoregion that contains a diverse range of interdependent flora and fauna. It also hosts numerous fronts: sharp boundaries between waters with different characteristics. As they strongly influence exchanges between the ocean, atmosphere and cryosphere, fronts are of fundamental importance to the climate system. However, rapid advances in physical oceanography over the past 20 years have challenged previous definitions of fronts and their response to anthropogenic climate change. Here we review the implications of this recent research for the study of climate, ecology and biology in the Southern Ocean. We include a frontal definition ‘user’s guide’ to clarify the current debate and aid in future research.

A study of Southern Elephant seals who inhabit Australia's most southern point, Macquarie Island is profiled. The researchers studied the behavior of the seals, including their ability to swim great distances in search of food.

The long‐held view that the East Antarctic margin is isolated from warm offshore waters has been challenged by recent observations showing incursions of warm modified Circumpolar Deep Water (mCDW) reaching several East Antarctic ice shelves. However, large areas of the East Antarctic continental shelf remain poorly observed, making it challenging to determine if the supply of oceanic heat to the ice shelves is changing. Here, we use temperature and salinity profiles to the west of the Shackleton Ice Shelf (SIS; ≈100°E) spanning 60 years to assess the variability of the water masses in the context of a changing climate. We document warming and freshening of shelf waters. Prior to 1996, cold mCDW water (θ< −1.6°C) was found below the surface mixed layer and cold Dense Shelf Water (DSW) with a salinity of >34.5 dominated the water column. After 2010, warm mCDW (≥−1.0°C) was widespread over the continental shelf and DSW with salinity over 34.5 was no longer present. The mixing ratio of glacial meltwater indicates that warm mCDW observed in 2011 caused basal melting of the SIS, possibly reducing the salinity of DSW. Increased access of warm waters to the continental shelf may have also occurred on the eastern side of the ice shelf, where glaciological evidence shows the grounding line has retreated. These observations suggest a shift occurred prior to 2011 that has increased the ocean heat supply to the continental shelf and to the SIS, increasing basal melt and reducing DSW formation. Recently, relatively warm waters that are normally found offshore are coming onto the Antarctic continental shelves, threatening the stability of East Antarctic ice shelves. The process, known as an “intrusion,” is mostly reported in West Antarctica. Yet, recent studies have documented similar warm water intrusions in East Antarctica. East Antarctica contains more ice mass than West Antarctica and thus, its potential contributions to sea level rise are also higher. It is not known if these intrusions have always happened, or if they started at a particular point in time. Much less is known about what mechanisms make them happen. This study shows warm water intrusions reach the Shackleton Ice Shelf from 2011 onwards. The intrusions melt the ice shelf from below and the freshwater resulting from this melt goes into the ocean and freshens it. It also increases the stratification of the water column, making it harder for polynyas, massive open ocean areas that form next to the Antarctic margins during the Austral winter, to produce an important dense water variety that supplies the bottom layer of the world ocean's circulation. Ocean observations spanning 60 years document a shift in shelf water properties west of the Shackleton Ice Shelf (SIS)Pre‐1996, modified Circumpolar Deep Water (mCDW) warmer than −1.6°C was not observed; post‐2010, warm mCDW (≥−1°C) was widespread to the west of the SISThe observed mCDW intrusions cause basal melt of the SIS, freshening Dense Shelf Water and hindering its production Ocean observations spanning 60 years document a shift in shelf water properties west of the Shackleton Ice Shelf (SIS) Pre‐1996, modified Circumpolar Deep Water (mCDW) warmer than −1.6°C was not observed; post‐2010, warm mCDW (≥−1°C) was widespread to the west of the SIS The observed mCDW intrusions cause basal melt of the SIS, freshening Dense Shelf Water and hindering its production

ABSTRACTPlastic marine debris is increasingly recognised as one of the greatest threats to global oceans, and the humans who depend on them. This study documents plastic ingestion in 24 species caught or sold for human consumption in the South Pacific. Fish were collected from local fishermen and markets in remote locations, including French Polynesia, Lord Howe Island and Henderson Island (Pitcairn group). Gastrointestinal tracts of 126 fish were visually examined and plastic was found in 7.9% of individual fish and 25% of species. The plastics were mostly microplastics (fragments, nurdles and rope). There was no significant difference in plastic ingestion in relation to feeding style, length, region or species. This is concerning as plastic appears to be widespread across species, lifestyles and habitats. This is the first report of plastic in South Pacific fish, raising concerns about the transfer of pollutants in a region that is largely oceanic and heavily dependent on seafood. The remote locations of the study also provide evidence of the widespread nature of this issue.

Coastal polynyas are key formation regions for dense shelf water (DSW) that ultimately contributes to the ventilation of the ocean abyss. However, not all polynyas form DSW. We examine how the physiographic setting, water‐mass distribution and transformation, water column stratification, and sea‐ice production regulate DSW formation in four East Antarctic coastal polynyas. We use a salt budget to estimate the relative contribution of sea‐ice production and lateral advection to the monthly change in salinity in each polynya. DSW forms in Mackenzie polynya due to a combination of physical features (shallow water depth and a broad continental shelf) and high sea‐ice production. Sea‐ice formation begins early (March) in Mackenzie polynya, counteracting fresh advection and establishing a salty mixed layer in autumn that preconditions the water column for deep convection in winter. Sea‐ice production is moderate in the other three polynyas, but saline DSW is not formed (a fresh variety is formed in the Barrier polynya). In the Shackleton polynya, brine rejection during winter is insufficient to overcome the very fresh autumn mixed layer. In Vincennes Bay, a strong inflow of modified Circumpolar Deep Water stratifies the water column, hindering deep convection and DSW formation. Our study highlights that DSW formation in a given polynya depends on a complex combination of factors, some of which may be strongly altered under a changing climate, with potentially important consequences for the ventilation of the deep ocean, the global meridional overturning circulation, and the transport of ocean heat to Antarctic ice shelves. Coastal polynyas are regions of open water surrounded by sea ice. As sea ice forms, it is pushed offshore by strong winds blowing from the Antarctic continent, keeping the polynya ice‐free. Salt is released into the water below as sea ice forms, increasing the salinity and density of the water column. In some polynyas, this water is dense enough to sink from the continental shelf to supply a network of bottom ocean currents that influences global climate. In other polynyas, the water in winter never gets dense enough to reach the ocean abyss. Using data collected by instrumented elephant seals, we investigated the main factors controlling dense water formation in four East Antarctic polynyas. We found that dense water production is related to the strength of sea‐ice formation, as expected, but also depends on the salinity at the start of winter. The geographical and physical characteristics of the polynyas and regional circulation also modulate the final water density. Our findings provide insight into how dense water formation in East Antarctic polynyas might respond to future changes in climate and thereby influence the transport of ocean heat to the Antarctic continent and the melt of ice shelves. We determined the physical factors enhancing (or hindering) dense shelf water (DSW) formation in four East Antarctic polynyas during a well sampled yearRelatively high salinity in early winter and high sea‐ice formation favor DSW formation in Mackenzie PolynyaThe properties and volume of DSW formed in a coastal polynya depend on its preconditioning as well as on sea‐ice formation We determined the physical factors enhancing (or hindering) dense shelf water (DSW) formation in four East Antarctic polynyas during a well sampled year Relatively high salinity in early winter and high sea‐ice formation favor DSW formation in Mackenzie Polynya The properties and volume of DSW formed in a coastal polynya depend on its preconditioning as well as on sea‐ice formation

Over the last decade, several hundred seals have been equipped with conductivity‐temperature‐depth sensors in the Southern Ocean for both biological and physical oceanographic studies. A calibrated collection of seal‐derived hydrographic data is now available, consisting of more than 165,000 profiles. The value of these hydrographic data within the existing Southern Ocean observing system is demonstrated herein by conducting two state estimation experiments, differing only in the use or not of seal data to constrain the system. Including seal‐derived data substantially modifies the estimated surface mixed‐layer properties and circulation patterns within and south of the Antarctic Circumpolar Current. Agreement with independent satellite observations of sea ice concentration is improved, especially along the East Antarctic shelf. Instrumented animals efficiently reduce a critical observational gap, and their contribution to monitoring polar climate variability will continue to grow as data accuracy and spatial coverage increase. A quality‐controlled collection of seal‐derived hydrographic data is presentedThe global value of seal data is assessed using a state estimation techniqueSeal data improve ocean circulation estimates in sea ice‐covered regions

The formation of Antarctic Bottom Water—the cold, dense water that occupies the abyssal layer of the global ocean—is a key process in global ocean circulation. This water mass is formed as dense shelf water sinks to depth. Three regions around Antarctica where this process takes place have been previously documented. The presence of another source has been identified in hydrographic and tracer data, although the site of formation is not well constrained. Here we document the formation of dense shelf water in the Cape Darnley polynya (65°–69°?E) and its subsequent transformation into bottom water using data from moorings and instrumented elephant seals (Mirounga leonina). Unlike the previously identified sources of Antarctic Bottom Water, which require the presence of an ice shelf or a large storage volume, bottom water production at the Cape Darnley polynya is driven primarily by the flux of salt released by sea-ice formation. We estimate that about 0.3–0.7×106m3s-1of dense shelf water produced by the Cape Darnley polynya is transformed into Antarctic Bottom Water. The transformation of this water mass, which we term Cape Darnley Bottom Water, accounts for 6–13% of the circumpolar total.

ABSTRACT Incidental seabird mortality associated with bycatch during longline commercial fishing is a conservation concern. An initial step to estimating likelihood of seabird bycatch and conceiving conservation strategies is determining amount of overlap between foraging birds and commercial fishing effort, identifying oceanographic features associated with foraging birds, and quantifying dive characteristics. We tracked 24 adult flesh-footed shearwaters (Puffinus carneipes) breeding on Lord Howe Island located east of Australia during incubation and early and late chick-rearing periods from 6 January to 17 April 2005. At-sea foraging distribution of flesh-footed shearwaters was primarily confined within the jurisdictional Australian Fishing Zone. Foraging was strongly associated with sea-surface temperature >24°C. Spatial and temporal overlap of longline fishing with foraging shearwaters varied throughout the breeding season, but was greatest (63% overlap) during early chick-rearing. Mean maximum distance reached from the breeding colony during a foraging event was 804 km (SD = 280) from Lord Howe Island. Foraging behavior was strongly diurnal, with 91% of dives occurring during daylight, and most dives (77%) were <5 m. Given that longline fishing and flesh-footed shearwaters overlap substantially, the Australian Fisheries Management Authority should consider implementing additional regulations to further reduce bycatch. Conservation strategies such as setting longlines at nights may reduce flesh-footed shearwater bycatch.

Reports findings of a research that investigated reasons behind the decrease in the populations of southern elephant seals. Implications of the decline for the rest of the Southern Ocean ecosystem; Discussion on potential factors that effected the decline in population; Information on a model for population regulation in the southern elephant seal.

This study investigated species recognition based on bark calls and full threat calls (FTCs) in three fur seal species, Antarctic Arctocephalus gazella, subantarctic A. tropicalis and New Zealand A. forsteri, that breed sympatrically and hybridize at subantarctic Macquarie Island. Bark calls, which are produced by males in male–female interactions, were more species-specific than their full threat calls, suggesting that bark calls could be used in species recognition and female mate choice. Further, the bark calls of A. tropicalis were more species-specific than those of A. gazella and A. forsteri, suggesting that divergence of calls between species is a consequence of phylogenetic distance, or has resulted from sexual selection through female mate choice. We believe the latter is more probable as we did not observe similar divergence in the FTCs of males. As such, the highly divergent bark calls of A. tropicalis may have resulted from sexual selection that has promoted pre-mating isolation via the process of reinforcement.

Pre-weaning growth rates, body composition, milk consumption and mass gain efficiency were measured in Australian fur seal Arctocephalus pusillus doriferus pups born in two consecutive breeding periods. Australian fur seals have the highest birth mass of any fur seal species (male 8.3 kg; female 7.2 kg). While their absolute pre-weaning growth rate (male 62 g·day−1; female 53 g·day−1) is similar to that of other temperate latitude fur seals, they have the longest birth-mass doubling time of any otariid species (134–136 days). Daily milk consumption increased from 400 g·day−1 (5 MJ·day−1) after birth to 675 g·day−1 (13.7 MJ·day−1) at age 210 day. However, mean mass-specific milk consumption (41 g·kg−1) is substantially lower than in other otariid species (58–70 g·kg−1) and, combined with a low mass gain efficiency (0.12 g·g−1), contributes to the low mass-specific growth rates observed. There were no significant differences in either absolute or mass-specific milk consumption between the sexes. Significant differences, however, were found between the sexes in the body composition of pups with females generally having larger body lipid stores than males for any given mass. Peak milk yield by Australian fur seal females is estimated at 0.60 MJkg−0.75, substantially less than in Antarctic fur seals. The low level of maternal energy transfer in Australian fur seals may reflect the relatively low marine productivity of their foraging areas.

The total body water (TBW) and body condition of 86 female southern elephant seals was estimated from tritiated water (HTO) dilution space analysis. HTO blood samples were analysed using two distillation methods (direct serum counts and evaporative freeze capture) that yielded significantly different estimates. Evaporative freeze capture is recommended for use because it is faster, cheaper, and provides a more precise TBW estimate of dilution space. Estimates of TBW were then compared with those derived from bioelectrical impedance analysis (BIA) and morphometric models. There were significant, positive relationships between TBW and BIA variables, but the level of accuracy was inadequate for BIA to be more useful than the other methods trialled. Morphometric models accurately estimated TBW (kg). Models developed from surface area (SA) (TBW = [SA * 82.58] – 86.94) and from a combination of mass (M), length (L), and girth (G) (TBW = [(M * 0.72) + (L * 5.49) + (G * 134.94) + 164.36)] provided the most accurate TBW estimates. In contrast, condition indices did not give accurate or reliable estimates of relative body condition.

The dive duration of 16 underyearling (6–12 months old) southern elephant seals Mirounga leonina during their second trip to sea was investigated using geolocating time–depth recorders. Underyearling seals had a lesser diving ability, with respect to duration and depth, than adult southern elephant seals. Individual underyearlings dived for average durations of up to 20.3 min and depths up to 416 m compared to durations and depths of 36.9 min and 589 m, respectively for adults. Dive duration was positively related to their body mass at departure, indicating that smaller seals were limited to shorter dive durations, perhaps as a result of their lesser aerobic capacity. All seals often exceeded their theoretical aerobic dive limit (average of 22.1 ± 18.1%). The number of dives exceeding the theoretical aerobic dive limit was not related to mass, suggesting that factors other than mass, such as foraging location or prey availability, may have been responsible for differences in diving effort. Foraging ability, indicated by the ability of the seals to follow vertically moving prey, was positively related to seal mass, indicating that small mass restricted foraging ability. The shorter dive durations of the smaller seals inferred that they had shallower dive depths in which to search for prey, thus restricting foraging ability. Although foraging ability was restricted by size, foraging success was found to be inversely related to mass, the smaller seals gaining a higher proportion of blubber than larger seals during their foraging trips. Thus, despite smaller seals being restricted to shallower depths and shorter durations, their foraging success was not affected.

Abstract. Observations were made of seabird and zooplankton distribution in the waters adjacent to south-easternTasmania to examine correspondence at coarse scales (tens of kilometres). The distribution of seabirds was related mainly to changes in the water depth (and distance from land) over the length of the transect, whereas the distribution of zooplankton related to temporal changes. Significantly different associations of seabird species occurred in Storm Bay (mainly species breeding within the bay), and over the shelf-edge (with many non-breeding species dominant). Zooplankton diversity varied during the study, being greatest at the beginning (May) and end (September) of the study. Little correspondence was found between the distribution of seabirds and zooplankton at the community level, but there were significant relationships for several species, such as diving petrels and gannets. The lack of an overall correspondence between seabirds and zooplankton may have been due to the patchiness of seabird and zooplankton distribution, limits to the requirements of seabirds to find maximum prey densities (instead only needing to find ‘enough’), the lack of certainty about whether seabirds were foraging when observed, and behavioural interactions among seabirds.

Adult male and female platypuses were radio-tracked in summer and winter at Lake Lea, north-western Tasmania. They appeared to exhibit greater diurnality, particularly during winter months, a greater degree of overland movement and more frequent use of non-earth refuge sites than do animals inhabiting mainland water bodies. Individuals foraged continuously for up to 16 h, with longer foraging bouts observed during the winter tracking period. Foraging range varied between 2 and 58 ha, with no significant differences observed between the sexes or seasons. All platypuses foraged predominantly in the lake; however, a number of animals were observed moving overland to and from waterbodies and burrows. Burrows were located on lake, creek and pool edges. A high percentage of burrows (25%) were located within dense sedge tussocks and scrub vegetation. Both the terrestrial activity and more opportunistic burrow-site selection may be related to reduced predation pressure in Tasmania.

We provide a detailed description of the spatial distribution, seasonality and transformation of the main water masses within MacKenzie Polynya (MP) in Prydz Bay, East Antarctica, using data from instrumented southern elephant seals. Dense Shelf Water (DSW) formation in MP shows large spatial variability that is related to the (a) local bathymetry, (b) water column preconditioning from the presence/absence of different water masses, and (c) proximity to the Amery Ice Shelf meltwater outflow. MP exhibits sustained sea ice production and brine rejection (thus, salinity increase) from April to October. However, new DSW is only formed from June onward, when the mixed layer deepens and convection is strong enough to break the stratification set by Antarctic Surface Water above and Ice Shelf Water below. We found no evidence of DSW export from MP to Darnley polynya, as previously suggested. Rather, our observations suggest some DSW formed in Darnley Polynya may drain toward the western Prydz Bay. Then, DSW is exported offshore from Prydz Bay through the Prydz Channel. The interplay between sea ice formation, meltwater input, and sea floor topography is likely to explain why some coastal polynyas form more DSW than others, as well as the temporal variability in DSW formation within a particular polynya. Coastal polynyas are regions of open water surrounded by sea ice. They form when strong winds from the Antarctic continent push newly formed sea ice away from the coast, as rapidly as it forms. Polynyas are therefore important sea ice factories. When sea ice forms, salt is released into the water below, increasing its salinity and density. The densest water in the World Ocean can be traced back to a few coastal polynyas along the Antarctic continent. This dense water formed in polynyas supplies the deep limb of a network of ocean currents that influences climate on global scales. Despite their importance, coastal polynyas remain poorly understood as they are difficult to reach and observe. Using data collected by instrumented elephant seals, we investigated seasonal changes in the MacKenzie Polynya in Prydz Bay, East Antarctica. Our study shows that dense water production is regulated by a complex interplay between three factors: strength of sea ice formation, the input of meltwater from ice shelves, and steering of the flow by sea floor topography. These new observations collected by seals contribute to a better understanding of dense water formation and the vulnerability of the global overturning circulation to future change. High resolution sampling of seasonal water‐mass evolution in MacKenzie Polynya reveals processes regulating dense shelf water productionDense water formation is concentrated in the relatively shallow western polynya where topography blocks inflow of Ice Shelf WaterThe interplay between sea ice formation, meltwater input and topography regulates the amount of Dense Shelf Water formed in coastal polynyas High resolution sampling of seasonal water‐mass evolution in MacKenzie Polynya reveals processes regulating dense shelf water production Dense water formation is concentrated in the relatively shallow western polynya where topography blocks inflow of Ice Shelf Water The interplay between sea ice formation, meltwater input and topography regulates the amount of Dense Shelf Water formed in coastal polynyas

Abstract: Cadmium and mercury concentrations were measured in the tissues of 64 individual albatrosses [23 wandering albatrosses (Diomedea exulans), 9 royal albatrosses (Diomedea epomophora) and 32 shy albatrosses (Thalassarche cauta)] which were killed as by-catch in longline fishing activities between 1991 and 1994. Mercury concentrations were also determined for 33 shy albatross eggs (excluding shells). The birds were all sexed and assigned to one of two age classes (immature and adult). The three species exhibited differences both in overall concentrations of cadmium and mercury, and also in the pattern of accumulation of metals with age and sex. Wandering albatrosses exhibited the highest mercury concentrations with a mean concentration in adult liver samples of 920.0 ± 794.1 μg g−1 dry weight. Shy albatrosses had the lowest mercury concentrations with mean concentrations in adult livers of 36.3 ± 21.4 mg g−1 dry weight. The highest mercury concentration was 1800 μg g−1 for an adult female wandering albatross. Cadmium concentrations were less variable, with adult royal albatrosses having the highest average concentrations (180.0 ± 165.0 in adult kidneys) and adult shy albatrosses the lowest (40.1 ± 20.0 in adult kidney). The highest individual cadmium concentration was 287 μg g−1 for a juvenile wandering albatross. There was no evidence of increased accumulation of cadmium with age in any of the species, but wandering albatrosses showed higher mercury concentrations in adults than juveniles. Female wandering albatrosses also had significantly higher mercury concentrations than males. The mercury contents of the shy albatross eggs were very low, with a maximum concentration of 5.4 μg g−1. The results of this study are consistent with the findings of previous work on albatrosses and support the notion that the life-history strategy of these species (i.e. long-lived with low reproductive output) may be an important determinant in the concentrations of some metals found in their tissues.

Thirteen female southern elephant seals moulting at Macquarie Island lost an average of 4.46±0.80 kg/day (10.01±1.20g/kg/day). There was no significant difference between this rate of body mass loss and that reported for moulting female southern elephant seals from South Georgia. Moulting female southern elephant seals however exhibited larger mass specific mass loss than either female northern elephant seals or male southern elephant seals, indicating a higher metabolic cost of moult in these animals.

Heart rate, swimming speed, and diving behaviour were recorded simultaneously for an adult female southern elephant seal during her postbreeding period at sea with a Wildlife Computers heart‐rate time depth recorder and a velocity time depth recorder. The errors associated with data storage versus real‐time data collection of these data were analysed and indicated that for events of short duration (i.e., less than 10 min or 20 sampling intervals) serious biases occur. A simple model for estimating oxygen consumption based on the estimated oxygen stores of the seal and the assumption that most, if not all, dives were aerobic produced a mean diving metabolic rate of 3.64 mL O2 kg−1, which is only 47% of the field metabolic rate estimated from allometric models. Mechanisms for reducing oxygen consumption while diving include cardiac adjustments, indicated by reductions in heart rate on all dives, and the maintenance of swimming speed at near the minimum cost of transport for most of the submerged time. Heart rate during diving was below the resting heart rate while ashore in all dives, and there was a negative relationship between the duration of a dive and the mean heart rate during that dive for dives longer than 13 min. Mean heart rates declined from 40 beats min−1 for dives of 13 min to 14 beats min−1 for dives of 37 min. Mean swimming speed per dive was 2.1 m s−1, but this also varied with dive duration. There were slight but significant increases in mean swimming speeds with increasing dive depth and duration. Both ascent and descent speeds were also higher on longer dives.

Antarctic krill (krill) are important within Southern Ocean ecosystems and support an expanding fishery. Toward understanding krill's response to environmental change, it is necessary to identify regions that support high krill larval production (spawning habitat). We develop a mechanistic model combining thermal and food requirements for krill egg production, with predation pressure post‐spawning, to predict regions of high‐quality spawning habitat. We optimize our model regionally and generate circumpolar predictions of spawning habitat quality. Our results indicate the southwest Atlantic accounts for almost half of all predicted high‐quality spawning habitat. Small‐scale management units (SSMUs) around the Antarctic Peninsula had high coverage of high‐quality spawning habitat. In contrast, the remaining SSMUs (except around South Georgia) were poorly covered, suggestive of population sinks reliant on input from external sources upstream. This implies strong potential for downstream impacts of fishing in key spawning areas, with implications for management of SSMUs and the krill fishery. Antarctic krill (krill) are a key prey item for many Southern Ocean marine predators and also support an expanding commercial fishery. However, there is a need to identify areas of the Southern Ocean that are best for both the production of eggs, and subsequent survival until free‐swimming larvae. We create a model for spawning habitat which considers the temperature and food conditions that adult female krill need to successfully produce eggs, as well as the density of predators feeding on spawned eggs. We optimize our model using existing regional‐scale data of krill eggs and larvae and use this to predict where good spawning habitat may exist around the whole Southern Ocean. Our model found that nearly half of the best spawning habitat occurs in the southwest Atlantic. Within this area, small‐scale krill fishing management areas around the Antarctic Peninsula contain good‐quality spawning habitat. Krill fished here are likely to be locally produced. But, other small‐scale management areas contain little good‐quality spawning habitat (except around South Georgia) and probably rely on krill being imported by ocean currents. This is important for understanding how fishing may impact both local ecosystems and those that are downstream. Mechanistic model for Antarctic krill spawning habitat uses thermal and food constraints on egg production, and predation on egg survivalOptimizing from regional data we generate circumpolar predictions to show half of quality spawning habitat is in the southwest AtlanticSpatial management units for the krill fishery do not all represent optimal spawning habitat, suggesting some areas rely on recruit import Mechanistic model for Antarctic krill spawning habitat uses thermal and food constraints on egg production, and predation on egg survival Optimizing from regional data we generate circumpolar predictions to show half of quality spawning habitat is in the southwest Atlantic Spatial management units for the krill fishery do not all represent optimal spawning habitat, suggesting some areas rely on recruit import

When to commence breeding is a crucial life-history decision that may be the most important determinant of an individual's lifetime reproductive output and can have major consequences on population dynamics. The age at which individuals first reproduce is an important factor influencing the intensity of potential costs (e.g. reduced survival) involved in the first breeding event. However, quantifying age-related variation in the cost of first reproduction in wild animals remains challenging because of the difficulty in reliably recording the first breeding event. Here, using a multi-event capture–recapture model that accounts for both imperfect detection and uncertainty in the breeding status on an 18-year dataset involving 6637 individuals, we estimated age and state-specific survival of female elephant seals (Mirounga leonina) in the declining Macquarie Island population. We detected a clear cost of first reproduction on survival. This cost was higher for both younger first-time breeders and older first-time breeders compared with females recruiting at age four, the overall mean age at first reproduction. Neither earlier primiparity nor delaying primiparity appear to confer any evolutionary advantage, rather the optimal strategy seems to be to start breeding at a single age, 4 years.

Diet is a fundamental aspect of animal ecology. Cetacean prey species are generally identified by examining stomach contents of stranded individuals. Critical uncertainty in these studies is whether samples from stranded animals are representative of the diet of free-ranging animals. Over two summers, we collected faecal and gastric samples from healthy free-ranging individuals of an extensively studied bottlenose dolphin population. These samples were analysed by molecular prey detection and these data compared with stomach contents data derived from stranded dolphins from the same population collected over 22 years. There was a remarkable consistency in the prey species composition and relative amounts between the two datasets. The conclusions of past stomach contents studies regarding dolphin habitat associations, prey selection and proposed foraging mechanisms are supported by molecular data from live animals and the combined dataset. This is the first explicit test of the validity of stomach contents analysis for accurate population-scale diet determination of an inshore cetacean.

New Zealand fur seals (Arctocephalus forsteri) are common in the Australian-New Zealand region, but vital demographic data are lacking. Accurate determination of the age of individuals is critical to the study of age-specific life-history parameters. A cross-sectional sample of female and male New Zealand fur seals was caught and animals were individually marked on Kangaroo Island, South Australia, between 2000 and 2003. Seals were aged through examination of a postcanine tooth, which was removed from each animal. Annual formation of cementum layers was confirmed and accuracy in age estimation was determined by examination of teeth removed from individuals of known age. Indirect methods of assessing reproductive maturity based on characteristics of mammary teats indicated that females 1st gave birth between 4 and 8 years of age, with an average age at reproductive maturity (ARM) of 5 years. No females were observed to breed beyond 22 years. Age of 1st territory tenure in males ranged from 8 to 10 years. Variation in ARM between individuals appears to be related in part to body size and condition. Classification of mammary teat status in combination with techniques for aging live animals provided a means of assessing ARM in the absence of extensive longitudinal data.

Reports on the 2002 Australasian Science Prize awarded to University of Tasmania Senior Lecturer Mark Hindell for his research on southern elephant seals swimming in the Antarctic waters. Cause of the decline in the number of the seals; Capability of the seals when in search for live food; Background on the scientific career of Hindell.

Numbers of male, female, and juvenile southern elephant seals (Mirounga leonina) hauled out on the isthmus of Macquarie Island were monitored for 14 months. Most haul-out patterns could be described by a normal distribution function. The value of using these normal distribution equations as predictive models was assessed. Equations describing the number of breeding females and the number of pups produced were found to be the most precise. Haulouts from other years at Macquarie Island, and from other populations were compared by means of parameters calculated by the function. It was concluded that there has been little change in the order or duration of haul-outs at Macquarie Island since the 1950s, and that there is remarkable synchrony in the timing of the haul-out of breeding females in all major southern elephant seal populations.

A longitudinal study of growth of southern elephant seals, Mirounga leonina, during their first foraging trip was undertaken at Macquarie Island. On average, body mass increased by 75% while foraging at sea, with individuals growing at 0.34 ± 0.12 (s.d.) kg day-1 (n = 64), and spending 182 ± 51 days (n = 64) at sea. Relatively smaller changes in body length were recorded during the same period, suggesting that growth was composed primarily of adjustments to body composition, rather than increases in gross body size. This may be in response to the functional demands of pelagic life. Body size established early in life (birth mass and departure mass) positively influenced body mass upon return from the first foraging trip. Growth rate, however, was negatively related to departure mass for females, and this is hypothesised to be related to sex differences in body composition, as well as intrasex differences in foraging skills, diving ability and food- conversion efficiency. Despite this, there was no detectable age-specific sexual dimorphism in the first year of life. Animals that were at sea longer tended to return in better body condition. Interspecific comparison suggests that southern elephant seals grow more than do northern elephant seals, Mirounga angustirostris, and this difference may be related to prey abundance and distribution.

The growth, maternal attendance and sucking behaviour of 11 New Zealand fur seal pups, Arctocephalus forsteri, on Maatsuyker Island, Tasmania, were studied during the first six months of lactation. Early growth rates (0–50 days) ranged from 78 to 138 g day-1 and were amongst the highest recorded for any fur seal. Male pups from Maatsuyker Island in 1993 grew at double the rate reported from Kangaroo Island in 1989 and 1990. Growth of pups was influenced by the attendance behaviour of mothers. Mothers that spent relatively long periods at sea had pups that grew more slowly. The proportion of time spent sucking by pups decreased during the attendance period of mothers. Distinct interannual variability was also determined for body masses of pups weighed in March in five successive years, 1990–94, with mean body mass differing by up to 20% between years.