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FALL 2013
Blue Corner is arguably Palau’s signature dive; it’s a
moderately shallow rock and coral plateau jutting out from an
inshore fringing reef with a sheer drop-off into deep water. The
site is renowned for excellent visibility and a strong current that
runs parallel to the edge of the reef. It offers divers a chance to
see schools of many different species of fish, such as chevron
barracuda, trevally, snappers and others. Sea turtles and sharks
cruise past in the blue, well within a diver’s field of vision. The
dive site is a crowd-pleasing favorite, and the majority of divers
surface delighted with the experience and absolutely unaware of
any impact they may have had on the site.
Once back aboard the boat, there will be mention, perhaps
even proud boasting, of seeing sharks “naturally” out in the
blue, unlike at other dive locations where scent attractions
are used to overcome sharks’ natural wariness. But upon
closer inspection this is a delusion. If you were to dive Blue
Corner without other divers you would discover an entirely
different Blue Corner. The schools of shining, silver chevron
barracuda that can just be seen in the distance during a high-
traffic dive are usually on the reef flat itself, above the sand
gullies and schooling between the coral heads. They’re not
out in the blue, among their predators and away from fish
they may prey upon. The same holds true for the schools of
trevally and snappers. These are reef fish, which by definition
are naturally inclined to stay on the reef. Even the sharks
would be above the reef flat, cruising among the coral heads,
patrolling their territory in search of unwary prey.
When a group of divers approaches a reef, moving along with
strong and determined fin kicks, fish see the divers’ physical
forms, and the silhouettes are unlike those of any other animal
likely to be encountered in the sea. Divers are rather large — of
a size generally associated with predators — and have what
appear to be two tails moving up and down. Then there is
the noise. Perhaps more than any other sound divers make,
the gurgle and bubbling of air exhaled through regulators is
incessant and very loud. This is especially true to animals with
acute acoustic sensitivity — a common adaptation in a medium
in which sound travels five times faster than in air. “The Silent
World” is anything but silent when scuba divers enter the sea.
Compounding the loud noise is the related effect upon a
fish’s “sixth sense”: its lateral line. The lateral line is a system
of sensory organs that aids in predator–prey interaction,
spatial awareness and orientation. It relays signals to the fish’s
brain about objects in the vicinity as well as continuously
monitoring the fish’s immediate surroundings, analogous in
practice to a proximity alarm or whiskers in mammals.
With these senses combined, fish not only can see the
physical form of an approaching diver and hear the noise
of the equipment, but they also can watch as the bubbles
emanating from a diver’s regulator float upward, expanding
as they ascend and manifesting the signature form of a large
inverted pyramid above the diver. In the sensory-processing
centers of a fish brain, this stimulus is generally alarming
enough to interrupt its routine and trigger its instinct to flee.
Somewhat tragic instances of diver displacement can occur
with egg-laying fish, which are extremely active and expend
a tremendous amount of energy to bring about the next
generation. They carefully tend to their nests of thousands of
embryos gestating within fragile, transparent eggs: They aerate
the eggs to make certain that oxygen-rich water bathes them
and to prevent the growth of algae; most important, they defend
those nutrient-rich eggs against predators until the young hatch.
A titan triggerfish may well be able to defend its egg nest
against a diver who inadvertently crosses into its protective
zone. The diver is perceived as a large predator by the
triggerfish, which is fearless and unrelenting in defense of its
territory against the hapless diver. The triggerfish will swim to
confront the diver at frenetic speed and perhaps bite a chunk
out of him with its formidable teeth and strong jaws. However,
while the triggerfish is on the offensive, opportunist egg-
eaters such as wrasses, surgeonfish and butterflyfish will take
advantage of the opening in defenses. They dart in to gorge
upon the momentarily unprotected eggs in an unabashed
frenzy, while the triggerfish deals with the intruding diver.
A similar outcome occurs when a diver strays too close
to fish such as the sergeant major damselfish. They lay their
nests of thousands of eggs upon rocks and protect them from
neighboring generalist predators; but rather than confront a
diver, the tiny damselfish flee in the interest of self-preservation,
abdicating their protective roles as guardians. The opportunists
instantly swarm, plundering gluttonously. In these situations,
the future fish generations are affected by inadvertent intrusion.
Divers who are more observant and situationally
aware — better able to read the reef and the behavior of
its inhabitants — and conscious of their impact on those
inhabitants can take measures to avoid interfering or at least
minimize the effects of their presence.
Divers have been frequenting some sites for 30 years or
more, and some animals have figured out how to use divers
to their advantage. This is especially evident on night dives
at some well-established sites in the Red Sea. As you swim
along in the perfect blackness of the night with your torch
illuminating finds here and there, a glance to the periphery
of your light’s beam will reveal one or more lionfish,
delighted to have a diver pointing out sleeping fish to be
gobbled up. Alas, these situations have become unavoidable
unless one wants to give up night diving entirely.
Some planned dives are unquestionably conscious
decisions to enter situations that may disrupt animals’ lives.
Visits to cleaning stations can be counted among these.
Cleaning stations are particular spots on a reef that are home
to various species of gregarious wrasses, whose niche on the
reef is to feed upon external parasites on the bodies of manta
rays and other large fish.
It’s easy enough to rationalize such excursions as not being
too intrusive. With careful planning, decent instruction, a
