Download Seabirds in the Marine Environment

ICES Journal of Marine Science, 54: 505–506. 1997
Seabirds in the Marine Environment
Introduction
Mark L. Tasker and James B. Reid
Seabirds have long attracted the attention of humans; in
ancient times they formed both a source of food and a
rich mythological tradition. The development of the
study of seabirds has followed the development of other
aspects of marine biology and ornithology. Much early
work involved studies at colonies and, indeed, some
seabird populations have probably the longest history of
detailed monitoring at their colonies of any marine
organisms. Systematic studies of the distribution of
seabirds at sea began in the 1920s and 1930s, notably
by Poul Jespersen and Vero Wynne-Edwards. While
these studies were mostly distributional in nature, they
did note changes in seabird communities with marine
parameters such as distance to land and water depth.
Seabirds are also part of the marine ecosystem,
usually as predators towards the top of the food chain,
but also as scavengers. As such, they can both influence
the food chain and be influenced by it. Most studies of
seabird diet and feeding have occurred at or near the
colonies, but increasingly studies have been carried out
at sea. Seabirds are influenced by human activities in the
marine environment, from being killed by oil pollution
to feeding on the waste discharged from fishing vessels.
Human influences on seabirds have been particularly
heavily studied in recent years.
Despite this interest in seabirds, our overall knowledge of seabirds and their ecology remains patchy. Their
relationship with the marine environment has proved
particularly difficult to study, owing mostly to practical
and logistical problems. It is comparatively difficult and
costly to go to sea. Seabirds may use very fine-scale cues
in exploiting the environment, often much finer or more
ephemeral than those that can be detected with our
instruments. Despite these problems, marine and pelagic
habitats and their influence on seabird dispersion and
behaviour are being studied increasingly. For example,
Ken Briggs and his co-workers carried out an integrated
study off California in the 1970s and early 1980s.
With this background, ICES decided to organize a
symposium on Seabirds in the Marine Environment,
co-sponsored by the Joint Nature Conservation Committee (JNCC) and the Seabird Group. ICES were
interested in all aspects of the marine ecology of seabirds, including potential interactions with fisheries.
Seabirds have been included within the ambit of ICES
activities only recently, with the establishment of the
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Study Group on Seabird–Fish Interactions in 1994 (now
the Seabird Ecology Working Group). JNCC is one of
the statutory UK bodies responsible for nature conservation. Both JNCC and its predecessor body have
supported extensive research on seabirds, focused on the
information required for their conservation. Of direct
relevance to this symposium, they have supported the
studies of the Seabirds at Sea Team since the late 1970s.
The Seabird Group is a voluntary charitable organization, based in the UK, with interests in both the study
and conservation of seabirds.
The symposium was held at Glasgow University,
convened by Mark Tasker (UK) and assisted by a
steering committee of Kees Camphuysen (Netherlands),
Bob Furness (UK), George Hunt (USA) and Jim Reid
(UK). There were five main themes, reflected in the
papers that follow. These were: (a) the nature of seabird
dispersion; (b) the identification and description of the
physical and biological processes that govern patterns of
dispersion; (c) foraging and feeding ecology of seabirds;
(d) energetic factors influencing seabirds; and (e) the
impact of fishing and fisheries on seabird populations.
Some papers did not fit easily into this framework,
while most had relevance to more than one theme. A
total of 22 papers and 30 posters were presented at the
symposium, and 22 of these appear as contributions to
this volume.
The two papers that are published here on the first
theme both derive from long-running at-sea survey and
research programmes, Ollason et al. link work carried
out in the North Sea to models of the physiology of
feeding, while Hüttmann and Lock present data from off
the eastern Canadian coast.
Papers on the patterns underlying seabird dispersion
were more numerous. These studies have been carried
out in a number of ways and at a number of different
scales. Wanless et al. examine the fine-scale distribution
of shags feeding off eastern Scotland using information
from a variety of sources including telemetry and studies
at sea. Away from colonies, Ribic et al. examine the
detailed influences of variations in hydrography in the
northern Gulf of Mexico. Similar influences are
described by Begg and Reid in the Irish Sea. At a larger
scale still, Garthe studied a variety of influences on the
distribution of seabirds in the south-eastern North Sea,
Wright and Begg explore the influence of sandeels on
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M. L. Tasker and J. B. Reid
guillemot distribution in the north-western North Sea,
and Ribic and Ainley investigate the relationships of
seabirds with aspects of their physical habitat in the
equatorial Pacific. The influence of marine habitat features on colony location of least auklets was examined
by Hunt (as well as the influence of physical features on
at-sea distribution). Montevecchi and Myers look at
the influence of decadal and longer-term changes in
oceanography and diet on the breeding distributions of
seabirds in the north-west Atlantic.
Harris and Wanless examine kittiwake diet and breeding success in a colony and describe the relationship of
these parameters with the quality of their sandeel food.
Knowledge of foods taken away from colonies is considerably more limited, so the studies by Lilliendahl and
Solmundsson in Icelandic waters are unusual. Seabirds
may link into the marine ecosystem at a number of
trophic levels. Munilla shows that swimming crabs are
an important part of the diet of yellow-legged gulls off
Galicia. Energetics of feeding and breeding are an
important factor in determining the diet and feeding
distribution of seabirds, and Grémillet demonstrates
that cormorants increased their foraging effort to
compensate for increasing demands of broods (and,
potentially, reduction in prey availability near colonies).
Hamer et al. also used colony-based observations to
describe the effects of differences in the feeding environment around colonies off northern and western Scotland
on the energetics of fulmar growth.
The effects of fisheries were examined in four papers
published here. Fulmars are major consumers of offal in
parts of the North Sea, but Camphuysen and Garthe
found that their occurrence at sea was not predicted well
by the distribution of discarded offal. The effects of
discards in the North Sea were also addressed by
Walter and Becker studying the brown shrimp fleet
fishing off the coast of Germany. Oro and Ruiz studied
scavenging birds behind trawlers in the north-western
Mediterranean. The effects of changes in the size of
fisheries on those species dependent on discards and
offal was studied by Chapdelaine and Rail in relation to
the cod fishery in the Gulf of St Lawrence.
The final three papers in this volume perhaps begin to
describe a little of what seabirds can tell us about the
marine environment. Jauniaux showed some physiological effects of oil contamination on dead birds. Briggs
et al. looked in more detail as to how these effects might
work, giving some clues as to how to treat contaminated
birds to allow for the impact of such stress on their
immune system. Finally, Furness and Camphuysen
review the usefulness of seabirds as monitors of the
marine environment. They conclude that while they may
act as reasonable indicators of marine contaminants,
they may be less useful, at present levels of understanding, as measures of the state of fish stocks.
The symposium was thus widespread and varied, and
a good indicator of the state of seabird science at
present. Studies are becoming more detailed, and it
is encouraging to see so many seabird biologists linking their work to that of other marine scientists to
examine issues common to a number of disciplines. The
next big step forward in relation to understanding the
ecology of birds at sea will come with the miniaturization and mass availability of devices for remote telemetry. Steps on this path are already beginning to be
made. A greater understanding of the physiology and
needs of seabirds will provide further fresh insight.
Additional studies on foods taken, particularly away
from colonies and outside the breeding season, are
also required if we are to understand both the impact
of seabirds on marine food chains and the impact of
fisheries on seabirds.
Mark L. Tasker and James B. Reid: Joint Nature
Conservation Committee, Dunnet House, 7 Thistle Place,
Aberdeen AB10 1UZ, Scotland, UK.