Parts of a Salmon and Their Functions
Eyes - As in humans, fish
eyes serve a variety of purposes - to seek out food, to avoid predators and other dangers, and, perhaps even to navigate in
the ocean. Fish do not have eyelids. They are constantly bathed in water and do not need tears.
Nostrils - Salmonids have
a well developed sense of smell and use this ability to seek out their home streams for spawning. In some cases this scent
is also helpful in avoiding predators. Fish breath through their gills, not their nostrils.
Lateral Line -
Fish do not have ears, as such. In part, low frequency sounds are detected in the water through a system of small holes along
each side of a fish called the lateral line, which is connected to a delicate system of nerves. They also react to medium
frequencies suggesting they detect these as well (this is not well understood at this time).
Mouth -
Fish use their mouth to catch and hold food of various types, but their food is not chewed before swallowing. In addition,
the mouth is a very important part of the breathing process. Water is constantly taken in through the mouth and forced out
over the gills.
Gills - Fish gills are composed
of two basic parts, the gill covers and the gill filaments. The gill covers protect delicate filaments and together with the
mouth force water containing oxygen over the gills. The gills are probably one of the most important organs of the body of
the fish. They are delicate but very effective breathing mechanisms. Gills are far more efficient than human lungs, because
they extract 80% of the oxygen dissolved in water, while human lungs only extract 25% of the oxygen in the air.
Gills are thin walled structures, filled with blood vessels. Their structure is arranged
so that they are constantly bathed in water. The fish takes in the water through its mouth. The oxygen dissolved in the water
is absorbed through the thin membranes into the fish's blood. Carbon dioxide is simultaneously released from the blood into
the water across the same membranes.
Fins - Salmonids
have two sets of paired fins (pelvic and pectoral) and four single fins (dorsal, caudal, anal, and adipose). Except for the
adipose and caudal fin, all the others are basically used to balance the fish in the water. The adipose is a small, fleshy
fin which serves no known purpose. the most important fin is the caudal. It acts like a rudder, and combined with the very
strong body muscles the fish, is their only means of propulsion. The caudal fin is also used by female salmonids to dig the
redds in which they deposit their eggs.
Scales - The bodies of salmonids
are protected by scales which grow in regular concentric patterns and can be used to determine the age and life history of
the fish. Over the scales is a layer of mucous (slime) which further protects the fish from disease organisms and helps it
slide through the water more easily.
Air Bladder - A membranous
sac filled with gas, situated in the body cavity of fish, ventral to the vertebral column, used to control buoyancy.
Esophagus - The
gullet, or esophagus, carries food from the mouth to the stomach.
Gall Bladder - The gall bladder
is a sac in which bile is stored.
Heart - A hollow,
muscular organ, the heart circulates blood through the body.
Intestine - The intestine
is found in the lower part of the alimentary canal extending from the pyloric end of the stomach to the anus.
Kidney - These
organs remove waste from the blood and produce urine.
Liver - A digestive,
storage and excretory organ.
Ovaries - The female reproductive
organs which produce eggs.
Pyloric Caeca - An appendage
in the form of a blind sac, connected with the alimentary canal, in which digestion takes place.
Spleen - The organ in which
white blood cells are produced and red blood cells are destroyed, in vertebrates.
Stomach - A sac-like
digestive organ receiving food from the esophagus and opening into the intestine.
Testis - The male reproductive
organ in which milt is produced.
Vent - The external
opening of the alimentary canal. Urine, feces, eggs and milt exit here.
