Can a new approach set the record straight?

Published on
March 3, 2010

Fish-in-fish-out (FIFO) ratios are much loved by environmental NGOs and researchers, who use them to calculate how much wild fish is needed to produce 1 kilogram of salmon. The latest papers estimate that it takes 4 to 5 kilograms of wild input to grow 1 kilogram of farmed, and this ratio is frequently used by opponents of salmon farming.

It was also quoted at a recent public hearing on aquaculture in the European Parliament, and caused MEPs to question once again, the sustainability of fish farming. Such a figure makes a good sound bite and sounds suitably outrageous. But is it accurate?

One of the problems with FIFO calculations is that they count the fish used in fishmeal and fish oil production separately, whereas in reality the meal and oil largely come from the same fish. They also do not account properly for the increasing use of trimmings, and these omissions produce inaccuracies in the calculations.

The International Fishmeal and Fish Oil Organization (IFFO) removes this double counting, and assumes that every scrap of fish meal and fish oil will be used up in feed for various species. This brings the FIFO ratio down to around 2:1. Arguably better than 5:1, but it still does not convince the green lobby of the benefits of aquaculture.

A new approach has been taken by fish feed manufacturer EWOS, which has revisited the controversy and taken into account the nutritional values of the fishmeal and fish oil, and of the resulting farmed fish. Their scientists argue that on a whole weight basis, farmed salmon contain around 20 percent fat, whereas wild caught fish used for fishmeal average around 7 percent fat. Taken on this simple scale, farmed salmon is an excellent way of increasing the nutritional value of fish used for human consumption. Weight-for-weight based calculations ignore the nutritional benefits and are biased against high fat species such as salmon and trout.

To redress the balance, EWOS last year proposed the use of nutrient ratios, which allow for a comparison between different farmed species, even though there are differences in their body composition. Their new calculations showed that it takes just 1.2 kilogram of marine ingredients to produce 1 kilogram of salmon, making salmon farming close to becoming a net seafood producer, i.e. providing more fish protein for human consumption than that removed from the ocean to make salmon feed.

Now EWOS scientists have gone even further, with their latest salmon feed trials achieving a marine nutrient ratio below 1:1, whilst maintaining good fish growth rates and feed efficiency, and still meeting the omega-3 fatty acid requirements of the consumer. Using separate calculations of nutrient ratios for proteins and fats, the marine protein dependency ratio was found to be 0.7:1, and the marine oil dependency ratio 0.9:1.

Their researchers also applied the nutrient ratio formula to historic data and found that dependency on marine proteins was higher than that of marine oils in 1997, but that by 2007 they were almost equal. This significant development was hidden by the use of simplistic weight-based ratios that do not separate out the different elements, and will be useful when reformulating feeds. 

Over the next few months, EWOS will be making public the results of its research. The company also aims to engage with the green lobby and those who influence industry, in a bid to convince them of its significance. It will be interesting to see how successful EWOS is in “selling” its research findings. Perhaps the European Parliament would be a good place to start.

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