Over the past few months I have received many questions about the dependence the salmon aquaculture industry has on the harvest of wild fish. These questions are good ones and I would like to offer a fairly detailed discussion here. After all, catching fish to feed the fish we eat is at the heart of the question of whether aquaculture is sustainable or not.
Allow me to begin with a bit of introduction.
Salmon, like people, get their Omega‐3s from their diets. Currently these Omega‐3s come from fish oils provided by fish that are captured and rendered (processed into fish oil and fish meal). A considerable demand is placed on wild-caught feeder fish populations to produce fish oil and the fewer feeder fish we use in salmon aquaculture, the more sustainable our salmon farming will be.
Measuring the relationship between wild fish caught to produce an amount of salmon is the “fish in, fish out” ratio, or what the industry calls the Feeder Fish Dependency Ratio (FFDR). FFDR measures the amount of wild fish used to raise a given amount of salmon. The wild fish are captured to provide both fish oil and fish meal. However, in the case of salmon, the dependency on fish oil from wild caught fish exceeds the dependency on fish meal. Thus FFDR for salmon is a measure of the capture of wild fish for the fish oil they provide.
The calculation below is extensively described by the World Wildlife Fund Salmon Aquaculture Dialogue standards.
Briefly, however, the calculation is this:
Where FCR = Feed Conversion Ratio = kgs of total feed consumed per kg of salmon grown
Let me illustrate with an example. In the bottom half of the equation, for every kilogram of feeder fish caught and rendered, the yield is 40-60 grams of oil. The top part of the equation is the amount of fish oil that goes into farmed salmon’s diet. It ranges widely but the average used by Dr. Albert Tacon of the University of Hawaii for the World Wildlife Fund (see notes below) is 200 grams of fish oil in 1 kilogram of salmon feed (the actual range is probably more like 170-230 grams). There is also significant variability in how much food is needed to raise 1 kilogram of salmon. (the FCR). A reasonable average is 1.2
When you calculate FFDR using all these numbers, you arrive at a range from 3.4 to 6.9. There is, of course, variability amongst different salmon growers. The average of all producers, however, will be something near an FFDR of 4.
To reinforce this, quite fortunately there is a completely independent path to arrive at the same conclusion. For the year 2008 approximately 2.3 million tonnes of salmon were produced worldwide (FAO ftp://ftp.fao.org/fi/stat/summary/summ_08/b-1.pdf) Again, assuming 1.2 kg of feed to produce 1 kg of salmon this means 2.76 million tonnes of salmon feed were produced. With 17% of salmon feed being fish oil this equates to the capture of 9.4 million tonnes of feeder fish. Thus, the global FFDR for salmon production is 4.09.
Looking through two different lenses one ends up viewing the same picture. Namely, it takes roughly 4 kg of captured fish to provide the fish oil necessary to grow 1 kg of salmon. From a global environmental perspective, this is the cost incurred by the wild fisheries that provide the fish rendered to feed salmon. (Recall above that I mentioned that fish are rendered to provide both fish oil and fish meal into salmon diets. This exercise can also be applied to fish meal. When you do that, however, you find that the largest driver for the harvest of wild caught fish for salmon aquaculture is fish oil.)
For an individual farm the WWF/Tacon methodology is the most rigorous way to describe the demand placed upon wild fisheries to grow farmed salmon. The Tacon method as employed by the WWF Salmon Aquaculture Dialogue is how we at Verlasso describe our call on ocean fisheries resources. It is the method we use to conclude the industry FFDR is around 4 and that the Verlasso FFDR is 1.
Notes for further reading
The WWF’s Dialogues are the process to develop standards for sustainable farming for many species. A draft set of standards was recently published for salmon (www.fair-fish.ch/files/pdf/english/sat2_salmon_draft.pdf. A full description of FFDR is contained in Appendix IV.)
For those of you inclined to do more in depth study I highly recommend the excellent book by Paul Greenberg Four Fish: The Future of the Last Wild Food. The chapter Salmon: The Selection of a King is an excellent overview of salmon aquaculture and its relationship to wild fish.
For every detail you would ever want to know, Albert Tacon wrote a review on aquaculture diets for the World Wildlife Fund’s Salmon Aquaculture Dialogue. Information on WWF’s Dialogues can be found at: http://www.worldwildlife.org/what/globalmarkets/aquaculture/salmon-additionalresources.html
Dr Tacon’s paper written on feed use for the Aquaculture Dialogues can be accessed at: http://wwf.worldwildlife.org/site/PageNavigator/SalmonSOIForm
 The WWF in its Salmon Aquaculture Dialogue is in the process to develop standards for sustainable farming of salmon. A draft set of standards was recently published for salmon (www.fair-fish.ch/files/pdf/english/sat2_salmon_draft.pdf. ) A full description of FFDR is contained in Appendix IV.