The animals on the cover of CSS: The Definitive Guide,Third Edition,are salmon
(salmonidae),which is a family of fish consisting of many different species. Two of
the most common salmon are the Pacific salmon and the Atlantic salmon.
Pacific salmon live in the northern Pacific Ocean off the coasts of North America and
Asia. There are five subspecies of Pacific salmon,with an average weight of 10 to 30
pounds. Pacific salmon are born in the fall in freshwater stream gravel beds,where
they incubate through the winter and emerge as inch-long fish. They live for a year or
two in streams or lakes and then head downstream to the ocean. There they live for a
few years,before heading back upstream to their exact place of birth to spawn and
Atlantic salmon live in the northern Atlantic Ocean off the coasts of North America
and Europe. There are many subspecies of Atlantic salmon,including the trout and
the char. Their average weight is 10 to 20 pounds. The Atlantic salmon family has a
life cycle similar to that of its Pacific cousins,and also travels from freshwater gravel
beds to the sea. A major difference between the two, however, is that the Atlantic
salmon does not die after spawning; it can return to the ocean and then return to the
stream to spawn again, usually two or three times.
Salmon, in general,are graceful,silver-colored fish with spots on their backs and
fins. Their diet consists of plankton,insect larvae,shrimp,and smaller fish. Their
unusually keen sense of smell is thought to help them navigate from the ocean back
to the exact spot of their birth,upstream past many obstacles. Some species of
salmon remain landlocked, living their entire lives in freshwater.
Salmon are an important part of the ecosystem, as their decaying bodies provide
fertilizer for streambeds. Their numbers have been dwindling over the years,
however. Factors in the declining salmon population include habitat destruction,
fishing, dams that block spawning paths, acid rain, droughts, floods, and pollution.