Page 89 - Fish and Amphibians (Britannica Illustrated Science Library)

84 PEOPLE, FISH, AND AMPHIBIANS FISH AND AMPHIBIANS 85

Large-Scale Catch Commercial Fishing Trawl nets

Commercial fishing fleets use advanced technology to detect consist of a cone-shaped body Overfishing
schools of fish, and they use enormous nets of three types: mesh closed by a sack in which the fish The fishing industry is an important source of food
he international demand for fish and shellfish has encouraged the use of nets, dragnets, and sweep nets. Fish species that are not used for are gathered. These nets are and employment around the world, and it provides
human consumption are also targeted commercially. maneuvered from one or two ships. the world's population with 16 percent of all animal
highly efficient fishing vessels and techniques. The use of these vessels and protein consumed. However, environmental pollution,
T techniques, however, has brought about increasing destruction of these Purse seines, or surrounding nets 1.24 miles climate change, and irresponsible fishing practices are
hang from floats and are dragged in a circle (2 km) taking their toll on the planet's marine resources.
resources and of the environment. Every year, fishing nets kill more than 300,000 around a school of fish. Then they are closed
whales, dolphins, and porpoises worldwide. The greatest threat facing many species is to at the bottom. These nets are ideal for OF ALL
catching surface species such as tuna and 10% SPECIES ARE
become enmeshed in the nets. sardines. EXTINCT OR
RECOVERING.

Traditional Fishing Local vessels billion Algae supply
fish in surface waters. Collected as food or fertilizer, algae also provide the
Traditional fishing is a widespread, The fish they catch 71.5 dollars vegetable gelatin used to make ice Fishing boat with
small-scale activity practiced directly by are usually sold in the THE RECORD AMOUNT OF MONEY cream and toothpaste. a purse seine
fishermen using selective fishing surrounding area. EARNED BY THE FISHING INDUSTRY Trawl net
techniques. Such harvesting of fish and Trawler
shellfish is carried out with equipment
such as harpoons, hand nets, fishing rods,
and fish traps. The vessels may include
anything from pirogues to small
motorboats. Long-line fishing
Many short lines with hooks
Whaling hang from one main line.
Stone traps ship They are used to catch both
820 feet
strand schools of small fish (250 m) surface and deepwater fish.
when the tide goes out.

65 feet
(20 m)
Raking cockles
Cockles and other
shellfish can be Gill net Sonar waves
gathered at low tide are sent to
by raking the sand. Net traps the bottom.
are a series of cone-shaped The waves
nets with a cylinder at one bounce back
end. They trap fish that when they
swim with the current. encounter
Commercial fish.
Species 1,640 feet
(500 m)
100 feet
Of the 20,000 known species of fish, (30 m) Sonar
only 300 are targeted for catching.
Six of these represent half of the is used to detect large schools of
total catch. fish. Sonar waves are sent from the ship
and bounce off the ocean floor. When they meet
with a school of fish, they bounce back sooner.
33 feet
(10 m)
Great Producers
HERRING
Fishing is an important source of food and employment all
over the world. These figures are in millions of dollars.
7,000
SARDINE TUNA
6,000 6.6
Gill nets 5,000 4.1 4 3.9 3.6 3.5
Bag net hang below the sea surface like 4,000
MACKEREL This net is used to catch curtains, moving to the rhythm 3,000
lobsters, shellfish, and fish. The of the tides. Besides capturing
opening is designed so that the fish, though, they attract and 2,000
animal can enter the net easily catch many sea mammals and
ANCHOVY COD but cannot get out. aquatic birds, which then die. China Norway Thailand United Denmark Canada
States