They are Often known as the King of fish. Salmon are powerful, sleek, silver fish prized for both their sporting qualities and desirable culinary characteristics.
The name ‘salmon’ is given to several types of fish belonging to the Salmonidae family which spend their young life in fresh water and then migrate to the sea
where they mature into adults.
Salmon may travel huge distances in the sea to specific feeding grounds before returning to fresh water to reproduce. In a remarkable but poorly understood feat of navigation,
a salmon may find its way back to the specific river, tributary and even pool of its original birth.
Types of salmon
There are two main groups of salmon: Atlantic and Pacific which take their names from the oceans they inhabit.
Trout and char also belong to the Salmonidae family and also have sea-going varieties which follow a life cycle and habitat very similar to their salmon cousins.
Steelhead is the common name given to rainbow trout that migrate to the sea, and sea trout is the common name given to brown trout which migrate.
Arctic char also commonly migrate to the sea where they grow considerably. And, like salmon, these fish all make fine eating and offer superb sport.
In 2007 the aquaculture of salmonids was worth US$10.7 billion globally.
Salmonid aquaculture production grew over ten-fold during the 25 years from 1982 to 2007.
Leading producers of farmed salmonids are Norway with 33 percent, Chile with 31 percent, and other European producers with 19 percent.
Salmon aquaculture is a major contributor to the world production of farmed finfish.
Other commonly cultured fish species include: tilapia, catfish, sea bass, carp and bream. Salmon farming is significant in Chile, Norway, Scotland, Canada and the Faroe Islands;
it is the source for most salmon consumed in the United States and Europe. Atlantic salmon are also, in very small volumes, farmed in Russia and the island of Tasmania, Australia.
There are four major infectious diseases that affect salmon in industrial farming operations:
- Infectious Salmon Anaemia (ISA)
- Infectious Hematopoietic Necrosis (IHN)
- Bacterial Kidney Disease
One of the most devastating diseases is Infectious Salmon Anaemia (ISA). ISA was first detected in Norway in 1984. Since then, it has spread Scotland, eastern Canada and the USA. In 2007 an outbreak among Chilean salmon farms became an epidemic leading to the death or destruction of 70% of the country’s farmed salmon. Now for the first time the ISA virus has been detected in the North Pacific. See CAAR’s statement on the discovery of ISA in BC.
Infectious Hematopoietic Necrosis (IHN) is a virus that affects both wild and farmed salmon. Sockeye, chinook, coho, rainbow trout and Atlantic salmon can all contract the virus, but Atlantic salmon are particularly susceptible. IHN is a virus and not a bacterial infection and infected fish are not treated with antibiotics.
Furunculosis is another highly infectious disease. It is caused by the bacterium Aeromonas salmonicida, Both Atlantic and Pacific salmon are susceptible to this disease at all stages of their lifecycle. It causes large boils to appear on the surface to the skin.
In 2005 furunculosis killed 1.8 million Atlantic salmon smolts at a single commercial salmon hatchery on Vancouver Island. The disease occurs in salmon farms throughout Scotland, Norway, Canada, the Broughton Archipelago in British Columbia, and Washington State.
Bacterial Kidney Disease is a chronic systemic bacterial condition of fish of the family Salmonidae caused by Renibacterium salmoninarum. Infection can result in significant mortalities in both wild and farmed salmonids. Nearly all age groups of fish can be affected, although the disease is rare in very young fish. Losses are generally chronic, occurring over an extended period. It affects fish in freshwater and seawater environments and can have a serious economic impact, particularly in seawater Atlantic salmon farms.
The first outbreak of bacterial kidney disease in farmed salmonids in Scotland was recorded in 1976. Since thn it has been found in salmon farming operations around the world.