Body Parts - External and Internal

External Morphology


Atlantic salmon are designed to be Tigers of the Water - sleek, and both fast and manoeuverable when necessary. They are able to conserve energy by lazily staying in one spot, and then quickly accelerate to high speed. The wild Atlantic salmon's fins are superb control surfaces. They allow it to cruise on course, or to turn quickly to left and right, or up and down.

The lateral line is an amazingly versatile sensory system. It can detect movement of other fish, but is perhaps even more valuable as a detector of water currents. It allows the Atlantic salmon to determine which direction is downstream, for movement to sea as a smolt.

The same lateral line assists the salmon to find its way upstream, and when a rapids or waterfall is encountered, it helps the salmon locate upwelling currents that will give it a boost in its jumping.

Internal Morphology

The beauty of wild Atlantic salmon is more than skin deep. Everything about this species is designed for survival and adapts the animal to the river and ocean environments in which it lives. Wild Atlantic salmon actually withdraw some of the blood from peripheral tissues during periods of high activity, to facilitate stronger muscle motion side to side, increasing available power.


The Atlantic salmon is capable of incredible bursts of speed and power, surmounting falls 12ft/4m high and reaching high speeds in the water, more than 30kph/20mph. The muscle of a wild Atlantic salmon comprises much of the body.


Transfer of dissolved oxygen from the water is efficiently handled by the 4 sets of gills. Finely subdivided, they allow survival even in warm less-oxygenated waters of mid-summer, while allowing the wild salmon to breathe easily in cooler water containing more dissolved oxygen.

Stomach, Pyloric Caeca, Gut

As in other creatures, these organs assist the salmon in digesting food. But from the time the ADULTS return to fresh water from the ocean, THEY NORMALLY DO NOT EAT! Instead they live off their body fat. The metabolism of the Atlantic salmon is somewhat like that of leopards - use minimal energy, except when you need a burst of power.

Swim Bladder

Allows the wild Atlantic salmon to maintain neutral buoyancy in the water, so is vital to it being 'at home' in the water. Some have said the first migration of the salmon as a very young fry is to journey from the gravel to the surface of the water to gulp a bubble of air for the swim bladder.


Wild Atlantic salmon have both rods and cones in the retina of each eye, giving them color vision. They also can detect polarization in light which may play a part in navigation. Atlantic salmon can see considerable distances in clear water, but how far is unknown.


The action of the mouth of the Atlantic salmon helps the animal move water over the gills, making far more efficient the oxygenation of the tissues within its body. Naturally the mouth also serves the purpose of catching prey, with a set of very sharp teeth, and a tongue in the bottom of the mouth which has taste sensing ability. A mouth also performs a function of being able to 'gulp air' and adjust the swim bladder's balance mechanism