Page 238 - NS-2 Textbook

OCEANOGRAPHY 233

The grmving use of tmderwater optical instruments, The danger of bemg attacked by a shark is exagger-
such as fixed television and camera lenses} has created ated in the minds of many people. The degree of hazard
fmther problems. Such lenses can be fouled m a very depends both on the location and on the numbers and
short tillle. Some kind of h'ansparent protective coatillg condition of the mdividuals m the water. Sharks are Wl-
must be developed before planned submerged television predictable and curious and will mvestigate ally object m
monitoring stations can be mstalled. the water. They are likely to attack the dead or the
Large stationary structures built on the contillental wOWlded. They have all exceptional ability to detect a
shelf for both rnilitalY alld commercial projects have ad- disabled or wounded anilllal at long rallge. Blood m the
ditional fouling problems. Offshore oil-drilling plat- water attracts and excites them through their sense of
forms, lighthouses, radar stations, and oceanographic re- smell.
search stations are generally intended to be permanent The largest of all fish m the ocean is the tropical whale
stnlctures. Fouling and deterioration by bacteria, flmgiJ shark, which may reach more than 45 feet in length alld
alld marme animals are serious threats to such platforms. weigh several tons. The basking shark and well-known
Submarme cables contammg telephone and electric great white shark, both fOWld m temperate alld tropical
power, and wlderwater pipelines, have been attacked by waters worldwide, may reach lengths in excess of 30 feet
shrilllplike anilllals called gribbles. They have gnawed and 20 feet, respectively. The tiger shark averages about 10
through wooden pilillgs alld rubber and plastic msula- feet in length but may reach as much as 20 feet.
tian. The famous teredo, or "shipworm/' can desh'oy Sharks are found m all oceans from 45 degrees north
wooden pilings, burrow into rocks and cement, weaken to 45 degrees south latihlde. The dallger of shark attack
stone seawalls, alld destroy msulation on cables. They appears to be greatest m tropical alld subtropical areas
have even drilled through solid lead sheathillg of sub- between latitudes of 30 degrees north and 30 degrees
marme power cables laid as deep as 7,200 feet! south. TIle most dallgerous areas are Australia, South
Africa, Cuba, and the Pacific coast of Pallama. In recent
times} however} an increasing nwnber of shark attacks
DANGEROUS MARINE LIFE have occurred on all coasts of the United States, espe-
cially off Florida beaches. No one knows for sure why the
People generally thillk of datlger at sea as attack by fear-
numbers of these shark attacks is rismg. One possible
some animals. Actually, atlilllallife m the sea is usually
cause is that the supply of fish m offshore areas upon
more helpful than harmful. Nevertheless, there are two
which the sharks normally feed may be decreasmg be-
categories of marme species that can be very dallgerous
cause of pollution and overfishillg. Although shark at-
to humans: carnivorous and poisonous or venomous.
tacks can result m serious mjmy, they are seldom fatal ex-
Camivorolls Allimais. Sharks are the leadmg carnivores
cept when the victim is small.
of most marme ecosystems. Of the 300 species identified,
The sharks considered most dangerous to people are
the larger species are the top predators m their envITon-
the great white shark, considered the most dallgerous of
ment. Although infrequent, shark attack remains a signif-
all; the tiger shark, probably the most common of tropi-
icant threat for bathers along the world's seacoasts alld for
cal sharks; the sand shark, native to East Indian waters;
people who work in the marine environment.
and the hammerhead shark, fOlmd throughout the
oceans m both tropical and temperate zones.
When sharks are present, people should not dangle
arms or legs m the water. Injured swilllmers should be
removed from the water quickly. Any flow of blood
should be stopped as quickly as possible. Dark clothing
and equipment are safest for s,vimmers. All movements
should be slow and purposeful to avoid attractillg
sharks; if they appear, swimnlers should remain per-
fectly still. Some sharks have departed when struck on
the snout, but this should be done only as a last resort be-
cause it could aggravate them.
Barraclida are extremely dallgerous. They may reach
6 to 8 feet long. TI1ey have knifelike catlille teeth and,
bemg swift swimmers, strike rapidly and ferociously.
Sharks have become an increasing threat to swimmers in recent They are feared more thall sharks in some areas of the
years. The danger of shark attack is greatest in tropical and sub- West Indies. FOlmd off the Florida coasts alld m the In-
tropical areas, but shark attacks have been recorded along all coasts
of the United States, especially off Florida. The white shark, above, dian and Pacific Oceans, they are attracted by almost ally
is the most dangerous of all. bright or colored object m the water and attack quickly.