The inshore fishes of Heard and McDonald Islands, Southern Indian Ocean

Using histological and cytological criteria, it has been shown that in the ovotestis of Serranus hepatus , a synchronous hermaphrodite, the differentiation of the ovary is earlier than that of the testis. Primordial germ cells (PGC) exhibit the same ultrastructural features in the ovary and the testis. These cells migrate from the ovary to colonize the testicular anlage.     

Differential expenditure of maternal resources in Antarctic fur seals, Arctocephalus gazella, at Heard Island, southern Indian Ocean

Maternal expenditure in lactating Antarctic fur seals (Arctocephalusgazella) was studied at Heard Island in the 1987 to 1988 summer/autumn.The mean birth mass, growth rate, and mass at 60 days of sonswere significantly greater than those of daughters. Maternalforaging trips lasted on average 5.9 days, and attendance boutslasted 1.5 days. Over the course of this study, foraging tripduration increased from 5.0 to 7.0 days, and attendance durationdeclined from 2.0 to 1.5 days. Pups lost 3.2% of their bodymass/day while their mothers foraged at sea, but gained massrapidly during periods of maternal attendance. Sons gained significantlymore body mass (1.9 kg) compared with daughters (1.3 kg) duringmaternal attendance, suggesting that sons consume more milk.Sex differences in mass gain were unrelated to pup age or bodymass. During 2-day maternal attendance bouts, sons gained mostof their mass (71%) during the first day, and daughters increasedmass at almost the same rate each day. The increase in massby sons during maternal attendance was significantly positivelyrelated to both the duration of their mothers' preceding andsubsequent foraging trips. In contrast, mass gained by daughterswas positively related to the duration of their mothers' attendance.Mass at 60 days age was negatively related to birth date insons, and positively related to birth mass in daughters. Thesedata indicate that (1) greater maternal resources are expendedon sons than on daughters, (2) sons receive greater maternalresources because they are male, and not because of their greaterbirth mass and body size, (3) different factors appear to beimportant in determining high postnatal growth in sons and daughters,and (4) demand for resources by sons can influence maternalbehavior and ultimately the level of resources received.     

Population status and breeding season chronology of Heard Island fur seals

Fur seals were eliminated by sealers at Heard Island soon after its discovery in the 1850s. The first recorded breeding of Antarctic fur seals (Arctocephalus gazella) since sealing was reported in early 1963 (two pups). The most recent survey of the Heard Island fur-seal population was undertaken between November 2000 and March 2001, when 1,012 Antarctic fur-seal pups were born. This represents a fourfold increase since the last complete census in 1987/1988 (13 years), when 248 births were recorded. Pup estimates and counts available for eight breeding seasons since 1962/1963 suggest the population has been increasing at between 12 and 20% per year. Based on pup production, the breeding population is estimated to number approximately 4,100 seals. The number of fur seals on Heard Island peaked in late February/early March at 29,256 indicating that, in addition to the breeding population, a significant number of seals born elsewhere haul out on the island. Most of these are moulting sub-adult and adult males. As in 1987/1988, only one subantarctic fur-seal pup (A. tropicalis) was observed, suggesting this species is not colonising the island, as has been speculated.     

The take of fish species by seabirds and marine mammals in the Australian Fisheries Zone around Heard Island: the potential for competition with a commercial fishery

. The number of predators from Heard Island foraging in shelf waters, their prey requirements, and the proportion of their diet that was commercial and non-commercial fish were estimated. The calculated annual consumption of commercial fish species varied between 36,360 and 84,166 tonnes. The non-commercial Krefftichthys anderssoni was the preferred prey for most predators, and when its occurrence in diets was low it was replaced by crustaceans and commercial fish species. The estimated annual consumption of Champsocephalus gunnari was approximately 2 and 6 times the highest and lowest estimates respectively of the biomass of this species, obtained from three fisheries research cruises. For Dissostichus eleginoides, the maximum estimate was 28% of the highest estimate of biomass. The current fishery for D. eleginoides will most likely impact on southern elephant seals, whose population decreased by 50% between the 1950s and the 1980s, possibly as a result of overfishing around Iles Kerguelen. Received: 26 January 1998 / Accepted: 20 April 1998     

The diet of feral cats at New Island, Falkland Islands, and impact on breeding seabirds

We studied the diet of feral cats (Felis catus) on New Island, Falkland Islands, through the analysis of 373 scats collected during the austral summers of 2004/2005 and 2005/2006. The most frequent prey were three introduced mammals (house mice Mus musculus, ship rats Rattus rattus and rabbits Sylvilagus sp.) and the thin-billed prion Pachyptila belcheri (each season present on ca. 21% of the analysed scats). These represent the first systematic data on feral cat diet for the Falklands. A simple bioenergetics model suggests that cats could be eating in the region of 1,500–11,000 prions per season, representing <1% of the local adult and subadult population. Predation on other seabirds nesting on New Island (several penguin species, albatrosses and cormorants) was unimportant, with the possible exception of white-chinned petrels Procellaria aequinoctialis, which nest locally in very small numbers. For each prion eaten, cats were estimated to have killed 1.1–1.9 ship rats during the summer season, and probably more in autumn and winter. Knowing that ship rats are prion predators, it is conceivable that, on the whole, cats are having a positive impact on the prion population, a scenario predicted by general theoretical models. Thus, considering the available information, we would not recommend the implementation of any eradication programme on New Island that would target cats in isolation. Nevertheless, it would be prudent to consider some local action targeting cats and rats around the small New Island white-chinned petrel colony.     

Lactation costs in southern elephant seals at King George Island,South Shetland Islands

Labelled-water methodology was used to quantify energy costs and energy transfer efficiency in 18 mother-pup pairs of southern elephant seals (Mirounga leonina) during lactation. During the lactation period, mothers lost a mean mass of 227±47 kg. Mass loss included 22% of the protein, 60% of the fat, and 51% of the energy in the mothers body upon arrival. Total body-energy reserves at parturition explained 69% of the variation in the total lactation costs and 50% of the variation in the pups body energy at weaning. On average, pups retained 48% of the mass, 49% of protein, 53% of fat and 51% of energy lost by their mothers. Greater, fatter females showed a decrease in the efficiency of energy and fat transfer and, at the same time, an increase in the efficiency of protein transfer. This may be due to an increased use of protein as metabolic fuel, as fat demands for milk production increase. There was no evidence that greater total lactation costs influence the ability of mothers to produce a pup in the next breeding season.     

Vegetation of the McDonald Islands, sub-Antarctic

The McDonald Islands (53°03^′S, 72°36^′E) are situated in the southern Indian Ocean, approximately 43 km west of Heard Island. These sub-Antarctic islands comprise McDonald Island itself, measuring ca.1 × 2 km, and two much smaller rocky outcrops, Flat Island and Meyer Rock. Five species of vascular plant occur on the islands. Only four species of moss were found, no hepatics, and eight species of lichen, together with algal and fungal species. Phanerogamic vegetation, comprising grassland and cushion-carpet herbfield, covers about one-third of the main island. Elsewhere, vegetation is absent or restricted to cryptogamic species. The distribution and occurrence of vegetation are strongly influenced by salt deposition, exposure to wind, substrate stability and biotic influences, particularly the very large assemblages of sea birds. The species-depauperate McDonald Islands are unique and have suffered negligible human impact. A management plan has been prepared; its implementation will be assisted by the information in this paper. The islands' protection will be further enhanced by an affirmative final decision on the current proposal for World Heritage Listing of Heard and the McDonald Islands. Received: 15 November 1996 / Accepted: 24 March 1997     

Vagrant Antarctic fur seals at the Tristan da Cunha Islands

Antarctic fur seals Arctocephalus gazella mainly breed at islands south of the Antarctic Polar Front, but stragglers occasionally occur farther north, with records from Gough Island (40°S, 10°W) in the central South Atlantic Ocean in October/November 2005 and September/October 2009. We report the first record from Tristan da Cunha (37°S, 12°W) in September 2013, and another individual that was observed at Gough Island. Both individuals were lean, lethargic subadult males that were present before the onset of the breeding (pupping) season of the resident populations of subantarctic fur seals Arctocephalus tropicalis.     

Fish prey of Antarctic fur seals,Arctocephalus gazella,during the summer-autumn period at Laurie Island,South Orkney Islands

The fish component in the diet of Antarctic fur seals, Arctocephalus gazella, was investigated at Laurie Island, South Orkney Islands from mid January to April 1988. Fish otoliths occurred in 78.8% of faecal droppings. Most of the otoliths extracted from scats belonged to Myctophid fish (93.4%), mainly Electrona antarctica and Gymnoscopelus nicholsi. These two fish species thus constituted the bulk of the diet. A greater percentage of the otoliths from G. nicholsi (31.1%) in this study were considered suitable for measurement in comparison with 10.3% from scats at Heard Island in 1990 and 11.4% at Macquarie Island in 1988/89. This lesser degree of erosion would suggest that foraging areas of fur seals during this study were closer to land than during previous studies. During the period studied, the commercial fishery around the South Orkneys was not based on Myctophid fish so there was no direct competition for fish between the fur seals and fisheries.     

Introduced mammals coexist with seabirds at New Island,Falkland Islands: abundance,habitat preferences,and stable isotope analysis of diet

The largest known colony of Thin-billed prions Pachyptila belcheri has been coexisting with introduced mammals for more than 100 years. Three of the introduced mammals are potential predators of adults, eggs and chicks, namely ship rats Rattus rattus, house mice Mus musculus and feral cats Felis catus. We here determine habitat preferences over three seasons and dietary patterns of the unique set of introduced predators at New Island, Falkland Islands, with emphasis on the ship rats. Our study highlights spatial and temporal differences in the levels of interaction between predators and native seabirds. Rats and mice had a preference for areas providing cover in the form of the native tussac grass Parodiochloa flabellata or introduced gorse Ulex europaeus. Their diet differed markedly between areas, over the season and between age groups in rats. During the incubation period of the prions in November–December, ship rats had mixed diets, composed mainly of plants and mammals, while only 3% of rats had ingested birds. The proportion of ingested birds, including scavenged, increased in the prion chick-rearing period, when 60% of the rats consumed prions. We used δ¹³C and δ¹⁵N to compare the importance of marine-derived food between mammal species and individuals, and found that rats in all but one area took diet of partly marine origin, prions being the most frequently encountered marine food. Most house mice at New Island mainly had terrestrial diet. The stable isotope analysis of tissues with different turnover times indicated that individual rats and mice were consistent in their diet over weeks, but opportunistic in the short term. Some individuals (12% of rats and 7% of mice) were highly specialized in marine-derived food. According to the isotope ratios in a small sample of cat faeces, rodents and rabbits were the chief prey of cats at New Island. Although some individuals of all three predators supplement their terrestrial diet with marine-derived food, the current impact of predation by mammals on the large population of Thin-billed prions at New Island appears small due to a number of factors, including the small size of rodent populations and restriction mainly to small areas providing cover. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Ingrid Schenk: deceased     

Changes in population sizes and distribution of fur seals at Marion Island

 Population censuses of the Antarctic fur seal (Arctocephalus gazella) and the sub-Antarctic fur seal (A. tropicalis) were conducted during the 1994/1995 breeding season at Marion Island. Pup numbers, determined from direct counts and a mark-recapture experiment, were used to estimate population sizes. Pup numbers of A. tropicalis showed a mean annual change of 2.0% over the previous 6 years, culminating in an estimated total population of 49, 523 for 1994/1995. The population appears to be entering the maturity phase of population growth and may therefore have recovered from the effects of uncontrolled sealing that ended in the early twentieth century. Numbers at the major colonies on Marion Island showed little change since 1989 and these sites may have reached carrying capacity. The extension of breeding to other parts of the island continues. Over the same period, A. gazella pup numbers showed a mean annual change of 17% and the total population numbered 1,205 in 1994/1995. This species has possibly entered the rapid recolonisation phase of population growth. A few hybrid seals were found. Received: 25 October 1995/Accepted: 14 April 1996     

Seasonal change in foraging areas and dive depths of breeding king penguins at Heard Island

The seasonal variation in the foraging behaviour of king penguins (Aptenodytes patagonicus) was studied at Heard Island (53°05′S, 73°30′E) during 1992/1993. On seven occasions throughout the breeding cycle, time-depth-light recorders were deployed on breeding adults to record the dive activities and foraging. Foraging locations changed with season: in autumn and spring 1992, adults foraged between 48–52°S and 74–78°E, about 370 km NNE of Heard Island close to the Polar Front. Two penguins tracked in winter travelled 2220 km east of Heard Island (95°E) along the northern ice limit, and 1220 km south of Heard Island to approximately 65°S, respectively. In spring (October), the penguins again foraged further north than during winter. The foraging area utilised in October overlapped the area where the penguins foraged in March/April. The penguins' diving behaviour also varied seasonally: the modal depth of deep dives (>50 m) increased from about 100 m in February to 220 m in October. Mean dive depths increased from 70 ± 52 m in March 1992 to 160 ± 68 m in August 1992. Penguins dived deep (>50 m) only during daylight hours (16 h in February, 9 h in July). Mean dive durations ranged from 2.9 ± 1.1 min in March 1992 to 5.1 ± 1.2 min in August 1992. Associated with changes in foraging location and dive behaviour was a change in diet composition: during summer the penguins ingested mainly myctophid fish (>90%) while in winter the most important diet item was squid. Accepted: 19 October 1998     

Growth of female southern elephant seals Mirounga leonina at Macquarie Island

Body growth of 137 female southern elephant seals (Mirounga leonina) over 1 year of age was investigated at subantarctic Macquarie Island. An asymptotic straight line, snout–tail body length of 2.57±0.03 m was estimated to be attained at 9 years of age, using a three-parameter Gompertz equation. A significant increase of approximately 0.1 m (5%) in mean body length of females between 1 and 10 years of age was estimated to have occurred between the 1950–1960s and 1990s at Macquarie Island. This is consistent with a reduction in both the rate of population decline and the age of onset of sexual maturity. Age determination using dental cementum layers and the importance of standardised measurements in pinniped growth studies are discussed.     

Behavioural and morphometric measurements of parental investment in southern elephant seals at the Falkland Islands

Parental investment is a key variable in the study of breeding strategies and life-histories evolution. In Pinnipedia, parental investment is usually calculated from direct measurements of pup weight gain or energy transfer between the mother and the pup. These direct methods always involve handling and restraining procedures that pose practical, logistical and ethical problems. To evaluate if weighing can be substituted by indirect observational estimates of parental investment, we analysed the relationship among various behavioural measures of suckling and post-natal growth in the southern elephant seal population of Sea Lion Island (Falkland Islands). Behavioural measures were in all cases a poor predictor of true investment as estimated by weighing. We concluded that there are currently no effective alternatives to direct handling, and that the best way to reduce the potential adverse impact of investment studies is the improvement of the handling protocol, which should include an estimation of the long-term effects on the health of handled animals. Further research is needed to test the validity of non-behavioural indirect methods (e.g. 3D photogrammetry).     

Breeding energetics and food requirements of gentoo penguins (Pygoscelis papua) at Heard and Macquarie Islands

The food and energy requirements of breeding gentoo penguins ( Pygoscelis papua ) were studied at Heard and Macquaric Islands by means of isotope turnover techniques.
The food consumption rates of chicks were measured at various stages of growth, providing estimates of the total food provided by adults to rear a chick to fledging.
The energy expenditures of attending adults were also measured at different stages of chick-rearing, allowing the total energy costs associated with breeding to be established for a pair of adults and at the population level on both islands. We estimate the total annual energy budget of a 6·2 kg breeding gentoo penguin to be 1517 MJ which is equivalent to the consumption of 292 kg prey.     

The distribution and composition of vascular plant communities on Heard Island

Summary Six major higher plant communities are defined for sub-Antarctic Heard Island: tussock grassland, meadow, herbfield, pool complex, cushion-carpet, fellfield. The communities were mapped at a scale of 1:50000, using colour aerial photographs and field observations. The floristic composition of twelve vegetation transects and of thirty sample quadrats along these is used to describe the communities and identify dominant or indicator species. The vegetation is compared with that of other sub-Antarctic islands.