Salmon Biology‎ > ‎

Overview


There are 5 species of Pacific salmon, all of which have been captured in the Northwest Territories.  Chum Salmon is the most common species of salmon captured, followed by Pink Salmon.  Chinook, Sockeye, and Coho Salmon have been captured, although they are significantly more rare.  Kokanee salmon, which are landlocked populations of sockeye salmon, have also been captured but are exceedingly rare. 

Where have Pacific salmon been captured in the Canadian Arctic? (click on map for larger, printable version)
  Map showing catch locations of all chum salmon captured and turned into Fisheries and Ocean Canada from
            2000-2011.  Map produced by the GIS Department, Aurora Research Institute.

Pacific Salmon Life-Cycle:
The general life cycle of Pacific salmon is similar among the species.  They are all semelparous, meaning they spawn once and then die.  They are also all anadromous, meaning they migrate to sea and return to freshwater to spawn.  There are populations of sockeye salmon, called kokanee, that do not go to the ocean.  
Sockeye salmon


Freshwater Stage:
All species of Pacific salmon return to a freshwater river, usually the river where they were "born", to spawn.  In the Northwest Territories, this migration seems to occur July - November.  The adults deposit their eggs and milt, the action called spawning, in a depression dug in the gravel of the riverbed by the female.  The adults then die.  

The salmon eggs develop in the gravel over the winter and the juvenile salmon emerge in the spring (see Figure below).  In the gravel, the salmon eggs develop into eyed eggs, which develop into alevins.  The alevins feed off their yolk sac while they are in the gravel.  Once their yolk sac is gone, they emerge from the gravel and are called fry.  Juvenile salmon can also be called parr (after the bars on their sides, called parr marks) or fingerlings.       
                                          
The development of fertilized eggs into salmon fry.













































































The next step is where the salmon species are different.  The chum and pink juveniles emerge from the gravel in the spring and head directly to the ocean that summer.  The Chinook, sockeye and pink juveniles emerge from the gravel in the spring and stay in the freshwater river system for at least one year before they head to the ocean.

Marine Stage:
Once in the ocean, all species of Pacific salmon eat and grow.  The length of time the salmon spend in the ocean depends on the species.  Chum Salmon spend 2-4 years in the ocean. Pink Salmon almost always spend one year in the ocean.  Chinook Salmon spend 2-5 years in the ocean.  Coho Salmon spend 1-2 years in the ocean.  Sockeye Salmon spent 2-3 years in the ocean before returning to freshwater to spawn.  

Their Changing Appearance:
All salmon undergo a change in appearance between what they look like in the ocean and what they look like when they are ready to spawn.  In the ocean, the salmon are silver, bright and are generally in excellent condition.  By the time the salmon have entered the freshwater river and swum far enough upstream to spawn, they look very different.  Salmon in spawning condition have changed colour.  In fact, the spawning colour of salmon depends on the species and it is used as a method to identify the different species of salmon.  The salmon are darker, the scales have reabsorbed into their bodies, they have lost a good deal of muscle and fat and are skinny, and their shape has even changed.  Salmon males develop a hooked jaw with elongated teeth.  The shape change in female salmon is present, but less pronounced.

   
        Chum Salmon in ocean bright silver colour                      Chum Salmon (male) in spawning colour

For more details about all 5 species of salmon, see our references.

Subpages (1): References