Abstract:
The massive number of seabirds (penguins and procellariiformes) and marine mammals
(cetaceans and pinnipeds) – referred to here as top predators – is one of the most
iconic components of the Antarctic and Southern Ocean. They play an important role
as highly mobile consumers, structuring and connecting pelagic marine food webs
and are widely studied relative to other taxa. Many birds and mammals establish
dense breeding colonies or use haul-out sites, making them relatively easy to study.
Cetaceans, however, spend their lives at sea and thus aspects of their life cycle are
more complicated to monitor and study. Nevertheless, they all feed at sea and their
reproductive success depends on the food availability in the marine environment, hence
they are considered useful indicators of the state of the marine resources. In general,
top predators have large body sizes that allow for instrumentation with miniature datarecording or transmitting devices to monitor their activities at sea. Development of
scientific techniques to study reproduction and foraging of top predators has led to
substantial scientific literature on their population trends, key biological parameters,
migratory patterns, foraging and feeding ecology, and linkages with atmospheric or
oceanographic dynamics, for a number of species and regions. We briefly summarize
the vast literature on Southern Ocean top predators, focusing on the most recent
syntheses. We also provide an overview on the key current and emerging pressures
faced by these animals as a result of both natural and human causes. We recognize
the overarching impact that environmental changes driven by climate change have on
the ecology of these species. We also evaluate direct and indirect interactions between
marine predators and other factors such as disease, pollution, land disturbance and
the increasing pressure from global fisheries in the Southern Ocean. Where possible
we consider the data availability for assessing the status and trends for each of these
components, their capacity for resilience or recovery, effectiveness of management
responses, risk likelihood of key impacts and future outlook.
