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Saturday, 10 June 2017

Climate Change, Over-fishing Threatening African Penguins – Scientists


A team led by Dr. Richard Sherley, from
the University of Exeter’s Environment
and Sustainability Institute, tagged 54
juvenile African penguins from eight
colonies and tracked them across their
breeding distribution.
Sherley said overfishing, combined with
environmental changes off western
South Africa, is dramatically reducing
populations of fish eaten by penguins in
the regions.
Changes in both the temperature and
salinity of the waters in the Benguela
ecosystem is causing fish to move east.
As a result, the young penguins are
hunting for food in the wrong places.
“The Benguela upwelling ecosystem is
one of the world’s most productive
ecosystems, but it’s also very heavily
influenced by human actions,” Sherley
told Reuters at the university’s Penryn
campus.
“There’s evidence of climate change
induced shifts in the Benguela which
have caused species to shift eastwards
and of strong impacts of fishing in parts
of the Benguela. In Namibia particularly
fish stocks, stocks of sardine, have
collapsed.”
Juvenile African penguins seek out
areas of low sea temperatures and high
chlorophyll-a, which indicates the
presence of plankton and therefore the
fish, such as sardines and anchovies,
which feed on it.
“When they (juvenile penguins) go to
sea for the first time, they’re not helped
by their parents and don’t have any
knowledge of where they might find
food. All they can do is follow cues that
they’ve evolved to detect. So they end
up where there’s no food and as a
consequence, the first year survival for
African penguins is very low,” said
Sherley.
Sherley says environmental degradation
causes maladaptive habitat selection so
that cues which used to work for a
species now put them in danger.
“They travel over thousands of
kilometres to get to these particular
locations. When they get there they’re
not finding the food that they need. The
human impacts have broken the system
in a certain way, so they’re getting
stuck in what’s known as an ecological
trap.”
The African penguin, once known as the
jackass penguin, is listed as endangered
by the International Union for
Conservation of Nature. The situation in
the Benguela ecosystem is worsening
their plight.
“Our population modelling suggests the
Western Cape population is about 50
per cent the size that it would be if this
trap wasn’t operating; the African
penguin is endangered. It’s declined by
more than 50 per cent over the last
three generations, so around 30 years.
The Western Cape population which
used to be the stronghold has declined
by about 80 per cent in the last 11 or 12
years.”
Sherley believes that fishing should be
suspended when prey biomass drops
below certain levels and says major
conservation action is required to save
the bird.
The research was carried out in
conjunction with the University of Cape
Town and published in the journal
Current Biology.

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