Page 223 - (DK) Ocean - The Definitive Visual Guide
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HORIZONTAL AND VERTICAL TRAVEL
Some animals migrate horizontally and
vertically. Here, longfin squid migrate
to spawn in May. They also move up and
down the water column each day to feed.
Navigation DAY NIGHT Vertical Migrations
While satellite tracking provides In temperate and tropical regions,
information on migration routes zooplankton migrates to the ocean
and confirms that many surface at night and then moves
individuals travel the same path, down again during the hours of
how animals navigate over vast daylight. In a single day, this vertical
distances is still poorly understood. movement may range from 1,310
Salmon return to their spawning phytoplankton phytoplankton to 3,300 ft (400 to 1,000 m),
grounds by smelling the unique depending on the size and type of
chemical composition of the mackerel animal involved. In polar regions,
water, but they first have to get where darkness lasts for several
close enough to pick up this scent. months, zooplankton migrates up
jellyfish
Some aquatic species may use and down on a seasonal basis, being
lanternfish
water currents to guide them, at the surface during summer and
while others use the Earth’s at depth in winter.
magnetic field to navigate. mackerel copepods It is thought that zooplankton
Animal migration is amazingly rises to feed on the phytoplankton
accurate, in terms of both shark that lives in the surface waters, but
direction and timing. Oceanic then retreats to depth for safety, or
birds, turtles, and mammals can squid possibly because it expends less
also navigate using the sun, the energy in cooler water. Maturing
stars, and familiar landmarks. planktonic larvae of animals such
660 ft (200 m)
as crabs will eventually migrate to
BELUGA WHALES MIGRATING copepods the sea floor and become benthic.
Belugas, like these in Lancaster Sound, squid
Canada, live in the Arctic and subarctic, but
some migrate to warmer waters in summer.
jellyfish
EARTH’S GREATEST MASS MIGRATION
During the day, when many animals remain
in the depths, out of sight of predators, the
shark phytoplankton utilizes the Sun’s energy to
produce food. At night, the biomass of the
surface waters (the sunlit zone) increases by
lanternfish as much as 30 percent, as zooplankton comes
squid up to feed on phytoplankton and is, in turn, OCEAN LIFE
eaten by various fish and other animals. This
regular movement of animals up and down
the water column is the greatest mass
3,300 ft (1,000 m)
migration on Earth.
