Abstract
The abundance and availability of food are critical determinants of reproductive
success and population dynamics of marine top predators. However, recent
work has indicated that the quality of the food may also be critically important
for some marine predators. The 'junk food hypothesis'’was originally suggested
as a potential explanation for a dramatic population decline of Stellers Sea Lions
Eumetopias jubatus in the Gulf of Alaska. According to the hypothesis, a dietary
switch to prey of low energy content led to detrimental effects on the population
of sea lions. A number of observations indicate that the hypothesis is relevant
for several population parameters. Recent work on piscivorous seabirds has
provided substantial evidence indicating the relevance of this hypothesis in food
webs in e.g. the North Pacific, the North Sea and the Baltic Sea. The emergence
of 'junk-food' in these systems may be coupled to large scale changes in
climatologically and oceanographic forcing, although predation, fishing and
competition provide additional plausible hypotheses. It may be possible to
predict which kinds of animals will be particularly sensitive to food quality: these
seem to be species with limited ability to carry food loads, with energetically-
expensive foraging behaviour, and with digestive anatomy evolved to minimize
mass at the cost of digestive efficiency. This review suggests that the junk-food
hypotheses is a highly relevant factor in relation to sustaining ecosystem
resilience, and is an important consideration in ecosystem management.
Sustaining healthy populations of marine top-predators requires an
understanding of the role of food quality, in addition to food abundance and
availability.
Keywords: none
http://dx.doi.org/10.1111/j.0030-1299.2008.16501.x
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