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Whale sharks are fish,and therefore they have no obvious
physiological requirement to swim at the surface (i.e.to
breathe
air) even though they are most often observed there during
‘seasonal ’ aggregations..Tracking studies indicate
that whale
sharks can dive to great depths (>1500m).They can remain
away
from the surface for long periods and this makes their movements
difficult to study.
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Whale sharks generally feed on very small planktonic prey (e.g.
krill,copepods,small fish etc.)that they ‘filter ’ from the water
using the fine mesh of their gill-rakers.Whale sharks are often
found in areas where large concentrations of this food source are
found.
The predictable annual whale shark aggregation at Ningaloo
Marine Park is closely linked with an increase in productivity of
the region associated with the mass coral spawn around March/
April each year.Similarly,their appearance at Christmas Island
appears linked to the red crab spawns in December/January.
Whale sharks are regarded as highly migratory -although their‘migration patterns ’ are
poorly understood..Research at Ningaloo Marine Park suggests that some sharks
undertake a northerly
migration when leaving the area.Limited satellite tracking data
combined with their seasonal appearance at Christmas Island
provides support for this theory.
Satellite tracking of whale sharks in US waters and also in the
South China Sea have revealed that whale sharks can travel great
distances (1,000s of kilometres).These migrations may take
years to complete.A far greater understanding of whale shark
movements will be possible with global ‘photo-tagging ’ via the
ECOCEAN Library in combination with limited satellite tracking
studies throughout the world.
As a giant filter-feeder,reliant upon large quantities of food from
seasonal ‘food pulses ’,the whale shark is potentially susceptible
to declines in productivity at its feeding locations.It is therefore
essential that migratory paths are confirmed and we more fully
understand which whale shark sighting locations are critical to
their survival.
Whale sharks are filter-feeders and pose no immediate threat to
humans.Whale sharks are very large and powerful animals and
should be treated with the utmost respect.Their tail in particular
has the potential to harm. |
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