By Asbjørn Bergheim*
Culture of this Pacific salmon species (Oncorhynchus kisutch) was initiated around year 1900 in the state of Oregon, USA, to improve fisheries and mitigate harmful human activity, such as dam construction. Seventy years later, the first cage-based farming of Coho took place in Puget Sound in Washington State. Over a 15-year period - from 1970 until the mid-80s -, its successful farming resulted in some 3,000 tons of Coho salmon produced per year. The harvested fish was a typical “pan-size product” of about 0.35 kg.
Nowadays, Chile has become the major producer of Coho salmon with 90% of the global production. The first stage of the industry in Chile was based on imports of eyed eggs from the Northern Hemisphere. The entire production cycle before the turn of the century took almost 3 years with stocking of 20-month old smolts of 60 – 80 g in sea cages and harvesting at 3 - 4 kg, 32 months from spawning. Today’s production in many Chilean farms is a 2 years cycle due to improved farming strategies, especially the use of freshwater with higher temperatures, and thus higher growth rates which make possible to harvest at 21 months of age. The harvest season is from late October until January.
Coho salmon grows best when the temperature is within 9 - 15 °C and is dependent on sufficient water exchange and supply of oxygen in the sea cage stage. Usually, the production cycle and the technology applied are not very different from Atlantic salmon farming. Coho is a rapidly growing species and utilizes feed in a very efficient manner - feed conversion ratios below 1:1 during on-growing are often reported. Besides, this species seems to be more resistant to some devastating diseases than other salmonids. A part of the traditional Chilean salmon smolt production has been performed in lakes, but freshwater cage farming is decreasing mainly due to reduced growth and negative environmental effects and is being substituted by more intensively run land-based systems.
Current situation of Coho culture
A predominant part of salmonids aquaculture in Chile was - and still is - run in the Pt. Montt - Chiloe Island region where a high number of cage farms is concentrated. The main farmed species, Atlantic salmon, was badly hit by the massive outbreak of infectious salmon anemia (ISA) and the produced volume dropped to half from 2008 to 2010. However, a part of the lost production was compensated as many farmers switched to Coho and steelhead trout, which are less vulnerable to the virus. The high resistance against ISA and also to a widely spread sea lice in Southern Chile (Caligus rogercresseyi), makes Coho a strong competitor to Atlantic salmon and trout.
Recently, this trend has reversed, with falling production volume of Coho. According to available statistics, the Chilean Coho production declined by 31% during the first half of 2014. The main reasons are protective measures against ISA and a generally higher export price for Atlantic salmon. Due to imposed governmental regulations, the number of farms in this region was strongly reduced after the ISA outbreak and the planned extension of the industry in the future is said to take place further south.
In British Columbia (BC), Canada, and Montana and Washington State, USA, there are some closed aquaculture facilities for Coho salmon culture to harvest size. Swift Aquaculture in BC raises Coho in freshwater tanks. This farm recycles its water due to RAS systems and is run as a multi-trophic site where the rich outlet water from the tanks is used to produce algae to feed crayfish. RAS-based production of salmon is rather costly, but Coho is a potentially well-paid niche product and the fish from Swift Aquaculture is sold to high-end restaurants in Vancouver.
Main market of Coho salmon
Ocean ranching of chum salmon in Japan probed to be the country’s only economically successful program ever. Chum fry are easy to produce, they present a good survival rate and the release of hatchery produced fry tripled the catches of this species during the program period (1980 – 95). More than 90% of the catches originated from released juveniles and the recapture rate increased from 1% to 3% during this 15-year period.
The global production of Coho salmon is around 200,000 tons, or about 1/10 of the Atlantic salmon production. Japan comes second as Coho producer globally, but is the leading Coho market with a share of more than 90% of the total volume. Thus, most of the Japanese consumption is based on imports from Chile. The production of Coho is to a great extent determined by the preferred consumer’s product in Japan which is 4 - 6 lb. fish sold frozen in supermarkets.
Dr. AsbjØrn Bergheim is a senior researcher in the Dept. of Marine Environment at the International Research Institute of Stavanger. His fields of interest within aquaculture are primarily water quality vs. technology and management in tanks, cages and ponds, among others.