Sharks The Animal Answer Guide

150 Sharks: The Animal Answer Guide

denticles on each gill raker. Trapped food is then moved to the throat by

tiny beating hairlike structures called cilia or by flushing of water across

the denticles. When groups of more than 30 mantas gather in areas of high

plankton density, they may line up and circle in a head-to-tail chain, re-

ferred to as cyclone feeding (see “Do sharks form schools?” in chapter 4).

Megamouth Sharks are rare deep-water animals that have only occa-

sionally been observed in healthy condition, so their feeding behavior is in-

ferred from their anatomy. They apparently engulf zooplankton much like

humpback whales, sucking in prey and water, a movement which expands

their mouth and throat. The engulfed prey and water is pushed across the

gill rakers as the mouth is closed and compressed.

When do sharks feed most?

Most sharks are true opportunists, feeding whenever a meal can be found.

But in general, sharks are more active at night than day. Increased nocturnal

swimming has been reported for water column species such as Gray Reef,

Blue, and Scalloped Hammerhead sharks, but also for bottom-living or rest-

ing species such as Port Jackson, Reef Whitetip, Horn, angel, and swell

sharks, as well as torpedo rays (see “Are sharks social?” in chapter 4).

As a result, shark fishing is most successful at night, although many

“nocturnal” sharks will also take baited hooks during the daytime. Noc-

turnal sharks often start being active at dusk and return to a resting area at

dawn, making evening twilight a period of greatly increased activity. For

example, telemetered Lemon Sharks doubled their swimming speed dur-

ing evening twilight as compared to their daytime or nighttime swimming

Whale Sharks feed primarily by
swimming through the water with
their mouths open. Water passes
into the mouth and out the gill slits.
Food items in the water flow into
the mouth and are trapped on the
filtering pads associated with the gill
rakers. At the bottom left, one entire
gill arch has been dissected from the
right side of the shark. The filtering
pads are the darker structures on the
right of this inset; the gill filaments
used in breathing are lighter and to
the left. Redrawn and used with permission
of Phil Motta from an original copyrighted by
Emily S. Damstra

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