siscowet

The most distinctive form of lake trout is the siscowet, found only in the deep waters of Lake Superior, typically at least 300 feet 90 m down.

Trout and Salmon of North America Robert J. Behnke 2002

Other lake trout are esteemed as fine food fish, but siscowet are considered to be inedible when fresh and are smoked to make them palatable.

Trout and Salmon of North America Robert J. Behnke 2002

The siscowet typically occurs from below 300 feet (100 m) to the greatest depths of Lake Superior at 1,333 feet (406 m), where the external pressure is 40 atmospheres.

Trout and Salmon of North America Robert J. Behnke 2002

The most extreme form of deep-water lacustrine specialization is found in a distinctive form of lake trout, the siscowet, in the depths of Lake Superior.

Trout and Salmon of North America Robert J. Behnke 2002

The siscowet, named Salmo siscowet in 1850 by Louis Agassiz, is still commonly recognized as a subspecies, Salvelinus namaycush siscowet.

Trout and Salmon of North America Robert J. Behnke 2002

The main difference between “normal” lake trout and the siscowet of Lake Superior is that siscowet have a much higher fat content.

Trout and Salmon of North America Robert J. Behnke 2002

Thus the air bladder of siscowet living at the great depths in Lake Superior would be inflated to about 20 times the pressure of a typical automobile tire.

Trout and Salmon of North America Robert J. Behnke 2002

Although virtually identical genetically to other lake trout of the Great Lakes, the siscowet is distinguished by its much higher fat content.

Trout and Salmon of North America Robert J. Behnke 2002

The siscowet occurs only in the deep, cold waters of Lake Superior at depths down to 1,333 feet 406 m.

Trout and Salmon of North America Robert J. Behnke 2002

The distended belly of the siscowet, pictured above, is most likely the result of an overinflated air bladder when it was landed.

Trout and Salmon of North America Robert J. Behnke 2002