Most of the Ross Sea has been designated a marine protected area (MPA), proposed ‘to protect ecosystem structure and function’. To assess effectiveness, the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) selected Adélie (Pygoscelis adeliae) and emperor (Aptenodytes forsteri) penguins, Weddell seals (Leptonychotes weddellii) and Antarctic toothfish (Dissostichus mawsoni) as ecosystem change ‘indicator species’. Stable for decades, penguin and seal populations increased during 1998–2018 to surpass historical levels, indicating that change in ecosystem structure and function is underway. We review historical impacts to population trends, decadal datasets of ocean climate and fishing pressure on toothfish. Statistical modelling for Adélie penguins and Weddell seals indicates that variability in climate factors and cumulative extraction of adult toothfish may explain these trends. These mesopredators, and adult toothfish, all prey heavily on Antarctic silverfish (Pleuragramma antarcticum). Toothfish removal may be altering intraguild predation dynamics, leading to competitive release of silverfish and contributing to penguin and seal population changes. Despite decades of ocean/weather change, increases in indicator species numbers around Ross Island only began once the toothfish fishery commenced. The rational-use, ecosystem-based viewpoint promoted by CCAMLR regarding toothfish management needs re-evaluation, including in the context of the Ross Sea Region MPA.

This article describes the natural history of a large colony of emperor penguins Aptenodytes for steri, its size, dispersal pattern of chicks, and associations with other bird and mammal species. A mid-season count of 19,364 chicks indicated that about 20–25,000 breeding pairs had been present in June and July. The colony was fragmented into several sub-groups which showed different mean sizes of chicks and survival to fledging. Other species observed included leopard seals Hydrurga leptonyx, the only major predators, which preyed heavily on both adults and fledging chicks. Fledgelings left the colony over a period of about 10 days; departure was an active process in which the chicks walked to the ice edge and dispersed in groups, swimming consistently southward. At this time they were still in about 60% down and weighed about 10 kg, having lost some 30% of the heaviest mass achieved during parental feeding.

During the austral summer of 1963–64 an investigation was started near “Mc-Murdo” on the diving habits of the Weddell Seal (Leptonychotes weddelli). The Weddell Seal was selected for this investigation because of some unique characteristics of its behaviour and because of the environment in which it occurs at McMurdo Sound, Antarctica. For eight to ten months of each year the sea ice provides a solid cover except for tidal cracks along the coast, pressure cracks between old and new ice, and scattered holes cut for oceanographic work. This gives the seals rather specific areas where they may surface in order to breathe. When they visit these breathing holes, instruments may be attached to them with a high probability that they will revisit the same hole and allow the investigator to remove the instrument. With this knowledge of the Weddell Seal' diving behaviour, it was my intention not only to gain some idea of the maximum diving epths and submergence times, but also to obtain information on such things as rates of descent and ascent, cruising depths and submarine orientation patterns. To determine these various parameters two types of instrument were needed, a depth-time device for recording dive profiles and a smaller, more easily attached unit that could be used to measure maximum depth of dives of a large number of seals.

The arrival in January 2001 in the south-west Ross Sea of two giant icebergs, C16 and B15A, subsequently had dramatic affects on two emperor penguin colonies. B15A collided with the north-west tongue of the Ross Ice Shelf at Cape Crozier, Ross Island, in the following months and destroyed the penguins' nesting habitat. The colony totally failed in 2001, and years after, with the icebergs still in place, exhibited reduced production that ranged from 0 to 40% of the 1201 chicks produced in 2000. At Beaufort Island, 70 km NW of Crozier, chick production declined to 6% of the 2000 count by 2004. Collisions with the Ross Ice Shelf at Cape Crozier caused incubating adults to be crushed, trapped in ravines, or to abandon the colony and, since 2001, to occupy poorer habitat. The icebergs separated Beaufort Island from the Ross Sea Polynya, formerly an easy route to feeding and wintering areas. This episode has provided a glimpse of events which have probably occurred infrequently since the West Antarctic Ice Sheet began to retreat 12 000 years ago. The results allow assessment of recovery rates for one colony decimated by both adult and chick mortality, and the other colony by adult abandonment and chick mortality.

During a cruise to the Ross Ice Shelf we counted all penguins and marine mammals seen whilst underway. Our objective was to determine the abundance and distribution of these animals along our cruise line. From 14 May until 11 June the sun was below the horizon. Our observations were from the 18 m high bridge. Most watches were in the dark, aided by the bridge spotlights. A total of 79 emperor penguins, 920 Adélie penguins, and 27 marine mammals were counted. We conclude that the Ross Sea, in which wildlife flourishes during the summer, is depauperate in winter. The low numbers of marine mammals may be due partially to their tendency to remain below the surface most of the time. However, Adélie penguins, a visual hunter which rests on sea ice at night, appear to prefer pack ice edges where there is a few hours of daylight and civil twilight for pursuit of prey. Non-breeding emperor penguins also rest on sea ice at night. All but four were observed north of the Ross Sea. Unlike more northerly colonies where females lay their egg and disperse in May female departure in the Ross Sea appears to be later and, we were unable to determine their winter foraging area.

Within the Western Ross Sea, there are six emperor penguin colonies of widely different size that occur exclusively on sea ice. In 1990 a survey of all six sites, two by close overflights and four from the ground, showed that the breeding habitats were highly variable. The most important physical characteristics of these habitats appear to be stable fast ice, nearby open water, access to fresh snow, and shelter from the wind.

Management of whale shark Rhincodon typus populations is hampered by a lack of information on the range travelled by individual whale sharks. This applies particularly in South-east Asia where the whale shark is increasingly used in commercial trade and for ecotourism. In this study an investigation of the movements of individual whale sharks from the greater Sulu Sea region was initiated using satellite telemetry. The movements of six sharks were monitored from 7 to 128 days. Two sharks travelled distances of 4567 and 8025 km. Both sharks moved through multiple political jurisdictions, confirming the need to manage the populations on a multilateral or regional level.