In two earlier blogs on fish oil supplements, I wrote about the lack of convincing evidence for some of the claims made about fish oils. We have discussed the evidence for and against the benefits of fish oils in great detail in our eBook: “Fish Oils – Everything You Want To Know” – available through this website. There is no doubt omega-3 fats, (specifically EPA and DHA), believed to be responsible for the beneficial effects of fish oils, are essential for the normal function of many of our organs, particularly the brain and retina. However, in some quarters, fish oils have been increasingly portrayed as a cure or treatment for almost everything. I have always been very skeptical of anything that is put forward as a universal cure or treatment. Nature just doesn’t work that way. And I am not alone in this, with others describing fish oils as the “Emperor’s New Pills” (1).
The fatty components of fish have uses other than as nutritional supplements. In this blog I want to talk about their use in the rapidly growing area of aquaculture.
Aquaculture is now a large international industry. The 2010 State of the World Fisheries and Aquaculture report by the Food and Agriculture Organization of the United Nations (FAO) illustrates this point very well. The FAO concluded that of the worlds wild fish stocks:
28% were overexploited;
8% were depleted;
and 52% were already fully exploited (2).
The report goes on to say that the top 10 species of fish comprising 30% of the world market are already overexploited. While these figures were for 2007, it is unlikely the situation will have improved since. With the world population due to reach 7 billion fairly soon and the rise of large and affluent middle classes in China, India and other parts of the developing world, one would expect the situation to get a lot worse.
Aquaculture has been proposed as a potential solution to the problem of overfishing and not surprisingly, the last decade has seen a rapid increase in this industry. The FAO has estimated aquaculture now accounts for nearly 40% of the total fisheries industry. However, before we get carried away and think aquaculture will solve all of our problems, we need to ask one question. What do we feed all the fish that will be grown using aquaculture? This is a very important question as many of the feeds used in aquaculture are made from fishmeal and fish oil derived from wild caught fish – A resource that is already over exploited! The FAO estimates that about a third of all wild fish caught is used for the production of fishmeal and fish oils for use in aquaculture. Given it can take around 5 kg (11 pounds) of fish food to produce 1 kg (2.2 pounds) of fish by aquaculture, this seems a rather inefficient way of doing things. And as the population increases, there will be even greater pressure on wild fish stocks for the fishmeal and fish oil requirements of aquaculture.
So with aquaculture on the increase and the wild fish stocks in decline worldwide, where will this extra fishmeal and oil come from? Fish oil is thought to be essential for the growing of fish by aquaculture. So where do you get fish oils from if you don’t get them from fish? There are a few potential alternative sources. One is oil from algae, fungi or bacteria. Some of these oils contain significant levels of omega-3 fats similar in chemical structure to the two principal omega-3 fats in fish (DHA and EPA) (3, 4). Another potential source of omega-3 oils are plant oils such as flax, canola, and soybean oil but these fats are chemically different from the two main omega-3 fats found in fish (DHA and EPA). There are also doubts whether yields of fish grown in aquaculture using these oils will be as good as those produced from fish oils and fishmeal. Another potential source of omega-3 oils are seed oils that are genetically modified to contain DHA and EPA (5). Again, there is little available information on how well fish would grow under aquaculture conditions using such oils. In addition, some consumers have concerns about the use of genetically modified feed for farmed fish. It is clear that economics will ultimately determine which of these oils may eventually replace fish oils – if they can.
There is yet another source, one just as plentiful that is already being used although to a limited extent in aquaculture. The source is krill oil. Krill are tiny crustaceans (shellfish) that abound in the oceans around the world, particularly the Antarctic. Krill are at the bottom of the food chain and serve as food for a huge number of fish and marine life such as whales. The largest creature to have ever lived on this planet – the Blue Whale – lives on krill. Krill oil is rich in polyunsaturated fatty acids, particularly the omega-3 fats that are essential for the growth of fish and humans alike. This is why there is such interest in using krill oil as a dietary supplement. There are similar health benefit claims made about krill oil (6,7) as for fish oils and it likely many more will be made as the marketing campaigns for krill oil supplements gain momentum. Like the claims made about fish oils, it will not be easy separating the hype from the facts, particularly as research into krill oil is still limited. It is important to stress that while fish and krill oils are both good sources of omega-3 fats, there are significant differences in the fat composition between them. Moreover, there are almost certainly a great variety of other substances present in krill oil and there are few scientific studies on the effects of these compounds on our health and wellbeing. The same caveats on the use of fish oil supplements mentioned in our book “Fish Oils – Everything You Want To Know” will also apply to krill oil.
While the amounts of krill caught at the moment may be sustainable, there are real concerns this will change and krill will become as overexploited as are other commercial fish. What is certain is the use of krill in aquaculture and as a supplement will increase. The main concerns are ecological and relate to the fact that krill is at or near the bottom of the food chain and, as a consequence, many marine animals and not just whales, are dependent for their survival on krill. It is difficult to predict the consequences of overexploitation of krill but overfishing of both the top and bottom parts of the marine food chain simultaneously is hardly likely to be beneficial to the survival of many marine animals. We will have to be careful. The ecological importance of krill has been recognized by the United Nations through the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR). CCAMLR was established to regulate exploitation of marine life in the Antarctic, rather than its outright protection. CCAMLR has already warned of the effects of increased catches of krill on marine life such as birds, seals and fish, which absolutely depend on krill for food (8).
It is fairly obvious there are potentially serious consequences for our food chain if we upset the supply of krill in the oceans. Much of the world’s population depends on seafood for survival – 1 in 5 some argue. So far our track record of managing valuable natural resources sustainably has not been good. Many of our most important wild fish stocks are under threat, in decline or have already been decimated through overfishing. Unfortunately, for a host of reasons, humans tend to think short term rather than long term. It is encouraging however that international bodies such as CCAMLR have been established to take a long term view. While individual governments around the world have begun to accept the need for conservation of important resources such as fisheries, they are under constant pressure from industry groups to relax any controls introduced. Let us hope good sense will prevail in relation to krill.
Meanwhile stay healthy and happy!
(1) O’Connell S (2010) “Omega-3: The emperor’s new pills.” New Scientist, 206, (2760) 32-34.
(2) State of the World Fisheries and Aquaculture, 2010 Food and Agriculture Organization of the United Nations (FAO), Rome, 2010.
Full report available online at: http://www.fao.org/docrep/013/i1820e/i1820e.pdf 
(3) Miller, M. R.; Nichols, P. D. and Carter, C. G. (2010) n-3 Oil sources for use in aquaculture–alternatives to the unsustainable harvest of wild fish. Nutr. Res. Rev. Dec; 21 (2), 85-96.
Abstract available online at: http://www.ncbi.nlm.nih.gov/pubmed/19087364 
(4) Ethier, S.; Woisard, K.; Vaughan, D. and Wen, Z. (2011) “Continuous culture of the microalgae Schizochytrium limacinum on biodiesel-derived crude glycerol for producing docosahexaenoic acid.” Bioresour Technol. Jan; 102 (1), 88-93. E-publication; 2010 May 31.
Abstract available online at: http://www.ncbi.nlm.nih.gov/pubmed/20570140 
(5) Venegas-Calerón, M.; Sayanova, O. and Napier, J. A. (2010) “An alternative to fish oils: Metabolic engineering of oil-seed crops to produce omega-3 long chain polyunsaturated fatty acids.” Prog. Lipid Res.. Apr;49 (2), 108-119. E-publication; 2009 Oct 24.
Abstract available online at: http://www.ncbi.nlm.nih.gov/pubmed/19857520 
(6) Ierna, M.; Kerr, A.; Scales, H.; Berge, K. and Griinari, M. (2010) “Supplementation of diet with krill oil protects against experimental rheumatoid arthritis.” EBMC Musculoskelet Disord. 11, 136.
Abstract available online at: http://www.ncbi.nlm.nih.gov/pubmed/20587038 
Full article available online at: http://www.biomedcentral.com/content/pdf/1471-2474-11-136.pdf 
(7) Ulven, S. M.; Kirkhus, B.; Lamglait, A.; Basu, S.; Elind, E.; Haider, T.; Berge, K.; Vik, H. and Pedersen, J. I. (2011) “Metabolic Effects of Krill Oil are Essentially Similar to Those of Fish Oil but at Lower Dose of EPA and DHA, in Healthy Volunteers.” Lipids 46 (1), 37-46. E-publication 2010 Nov 2.
Abstract available online at: http://www.ncbi.nlm.nih.gov/pubmed/21042875 
Full article available online at: http://www.springerlink.com/content/270j241473471664/fulltext.pdf 
(8) www.ccamlr.org http://www.ccamlr.org