Volume 448, 1 November 2015, Pages 365–374
Open Access
Abstract
In
1990, 90% of the ingredients in Norwegian salmon feed were of marine
origin, whereas in 2013 only around 30%. The contents of fish meal and
fish oil in the salmon feed were 18% and 11%, respectively, in 2013.
Between 2010 and 2013, salmon production in Norway increased by 30%, but
due to a lower inclusion of marine ingredients in the diet, the total
amount of marine ingredients used for salmon feed production was reduced
from 544,000 to 466,000 tonnes. Norwegian salmon farming consumed
1.63 million tonnes of feed ingredients in 2012, containing close to 40
million GJ of energy, 580,000 tonnes of protein and 530,000 tonnes of
lipid. 1.26 million tonnes of salmon was produced. Assuming an edible
yield of 65%, 820,000 tonnes of salmon fillet, containing 9.44 million
GJ, and 156,000 tonnes of protein were produced. The retentions of
protein and energy in the edible product in 2012 were 27% and 24%,
respectively. Of the 43,000 tonnes of EPA and DHA in the salmon feed in
2012, around 11,000 tonnes were retained in the edible part of salmon.
The retentions of EPA and DHA were 46% in whole salmon and 26% in
fillets, respectively. The fish in/fish out ratio
(FIFO) measures the amount of fish meal and fish oil that is used to
produce one weight equivalent of farmed fish back to wild fish weight
equivalents, and the forage fish dependency ratio (FFDR) is the
amount of wild caught fish used to produce the amount of fish meal and
fish oil required to produce 1 kg of salmon. From 1990 to 2013, the
forage fish dependency ratio for fish meal decreased from 4.4 to 0.7 in
Norwegian salmon farming. However, weight-to-weight ratios such as FIFO
and FFDR do not account for the different nutrient contents in the
salmon product and in the forage fish used for fish meal and fish oil
production. Marine nutrient dependency ratios express the
amount of marine oil and protein required to produce 1 kg of salmon oil
and protein. In 2013, 0.7 kg of marine protein was used to produce 1 kg
of salmon protein, so the Norwegian farmed salmon is thus a net producer
of marine protein.
Statement of relevance
This
manuscript shows the retention efficiency of nutrients from feed
resources to final product in the Norwegian salmon production, including
limiting resources such as the omega-3 fatty acids EPA and DHA and
phosphorous. It is highly relevant to compare the efficiency in
commercial scale with experimental data, and this is to our knowledge
the first attempt to make such calculations for an entire commercial
aquaculture production.
Keywords
- Feed resources;
- Production efficiency;
- Atlantic salmon;
- Nutrient retention;
- Omega-3 fatty acids
1. Introduction
The
world's population is currently increasing by 80 million each year, and
is expected to reach 9 billion by the year 2050. The Food and
Agricultural Organization of the United Nations (FAO) has predicted that
70% more food must be produced globally by 2050 to meet the increase in
demand. The population growth, combined with increased urbanisation and
higher per capita income in large parts of the world, changes consumption habits and puts pressure on the available resources. The per capita
meat consumption was 15 kg in 1982, when the world population was 4.5
billion, and is expected to reach 37 kg in 2030. This will have a large
impact on the environment and the available resources of land area,
fresh water, and phosphorus, and urgent action to develop food systems
that use less energy and emit less greenhouse gases is required ( FAO, 2011a).
The global food sector is currently responsible for around 30% of the
world's energy consumption and contributes more than 20% of the global
greenhouse gas emissions ( FAO, 2011b). In addition, land use changes, mainly through deforestation, contribute another 15% of greenhouse gas emissions.
Any
method of food production can be evaluated in terms of the influence it
has on the environment and how much natural resources are consumed in
the process (Bartley et al., 2007, Kates et al., 2001 and Singh et al., 2009). Eagle et al. (2004) defined ecologically sustainable food production
as production that maintains the natural capital on which it depends,
and that in principle can continue indefinitely. Well-managed fisheries
where the catch is regulated based on stock assessment fulfil this
definition. However, no industrial food production is truly sustainable
today, because all such productions depend on non-renewable energy
sources such as oil and gas, as well as non-renewable phosphorous
sources. Industrial food productions may be evaluated in terms of energy
produced in relation to the input of industrial energy ( Tyedmers et al., 2007).
When the sustainability of food productions is evaluated, the goal
should be to maximise the nutritional output for human consumption and
minimise the input of resources (organic and inorganic), with the lowest
possible impact on the environment. The nutritional content of food
products is easy to calculate, but it is more challenging to quantify
the use of natural resources and to assess the environmental effects of
different food production systems ( Schau and Fet, 2008).
All
food production has environmental consequences. Agriculture is the main
source of water pollution by nitrates, phosphates and pesticides, and
livestock production is a major source of greenhouse gases. Livestock
production uses large amounts of fresh water and land areas. The global
meat consumption is increasing by around 3.6% per year and has nearly
doubled between 1980 and 2004. It is expected to double again by 2030 (FAO, 2011b).
There is also a shift from extensive grazing systems to more intensive
production systems that depend on more concentrated feeds and feed
ingredients that are traded internationally. More than 30% of the world
cereal production is currently used in feed for livestock. Global food
production is also heavily dependent on the use of phosphorus
fertilizer. The low phosphorous concentration in soil in large parts of
the world makes it a limiting factor for plant growth on entire
continents such as Africa and Australia, and in many large countries
such as Brazil and India. Phosphorus is thus essential for global food
production, and agriculture consumed almost 90% of the P used in 2010,
82% was used in fertilizers and 7% was used in animal feed supplements (Schröder et al., 2009).
However, the current use of phosphorus is not sustainable. Phosphorus
is not recycled at present, but moves through an open one-way system in
which the phosphorus ends up in the ocean. A meat-rich diet consumes
three times as much P as a vegetarian diet, and for a world population
of 7.7 billion people, a 20% increase in phosphorous-fertilizer would be
required without changes in the world diet, whereas a 64% would be
required if the complete world population were to have a diet that
resembles the diet in developed countries (Smit et al., 2009).