10 Status and Future Perspectives in Aquaculture
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sively studied from the early 20th century in Europe and the USA, but is commercially used only in SE Asia where this type of mariculture has a stronger tradition
(Svåsand and Moksness 2004).
In traditional mariculture, the cultured species are maintained under strict control
in relatively intensive cultures (high biomass). One consequence is the need to
provide fish food. The availability of feed resources for aquaculture is believed to
become a main driver of mariculture development. Food resources are already
becoming limiting, particularly during El Niño events, when the major fisheries of
some of the upwelling regions in eastern Pacific and Atlantic waters can be greatly
reduced. The major bottleneck is, in fact, the availability of marine lipids (OpsahlFerstad et al. 2003). The feed companies are already adding more and more lipids
and proteins from land agriculture into fish feed, and a major part of their research
budgets over the past decade has been related to this specific task.
Marine species require food of marine origin for growth, or more specifically
they need to be supplied with long chain ω3 fatty acids such as DHA (22:6 ω3,
docosahexaenoic acid) and EPA (20:5 ω3, eicosapentaenoic acid). Such highly
unsaturated ω3 fatty acids (ω3HUFA) are only present in high amounts in marine
or aquatic organisms. Mariculture of marine organisms can therefore not easily be
based on lipids from agriculture, because the essential fatty acid composition is
different. Oils from higher plants are typically rich in ω6 fatty acids and short chain
ω3 fatty acids (e.g., 18:3 ω3, α-linoleic acid). This fact represents a major potential
constraint for developing mariculture during the next century, because the feed
resources in mariculture are not as easily available as the feed resources in agriculture (plants). Mariculture feed for most type of organisms is based on herbivore
animals that are harvested from wild stocks. It is therefore not obvious that mariculture
will become as successful as agriculture, because such wild stocks have a limited
availability (e.g., Myers and Worm 2003).
There are some potential ways to provide new marine fatty acids rich resources
for fish feed. An ultimate challenge is to reduce discards from fisheries; some 20
million tonnes year
−1 might then become available (Hall and Mainprize 2005).
Other options are:
●
Selected suitable oils (and protein) from agriculture – these resources can be
used to dilute the marine resources, but cannot replace them entirely.
●
“New” marine resources – a significant increased harvesting of resources can
only be achieved by harvesting at low trophic levels of the marine food web,
emphasizing the use of marine plants and herbivore invertebrates.
●
Production of “single cell biomass” using microorganisms with marine-type lipids,
ω3 HUFA rich.
●
Production of genetically modified organism (GMO) with marine-type lipids –
e.g., a transgenic microorganism (“single cell biomass”) or a higher plant with
ω3 HUFA genes transferred from algae
Use of resources produced in agriculture for mariculture will not contribute essentially to the world supply of food, and these conflicts are more easily seen from a
densely populated region as SE Asia than from western countries, where the general
305
sively studied from the early 20th century in Europe and the USA, but is commercially used only in SE Asia where this type of mariculture has a stronger tradition
(Svåsand and Moksness 2004).
In traditional mariculture, the cultured species are maintained under strict control
in relatively intensive cultures (high biomass). One consequence is the need to
provide fish food. The availability of feed resources for aquaculture is believed to
become a main driver of mariculture development. Food resources are already
becoming limiting, particularly during El Niño events, when the major fisheries of
some of the upwelling regions in eastern Pacific and Atlantic waters can be greatly
reduced. The major bottleneck is, in fact, the availability of marine lipids (OpsahlFerstad et al. 2003). The feed companies are already adding more and more lipids
and proteins from land agriculture into fish feed, and a major part of their research
budgets over the past decade has been related to this specific task.
Marine species require food of marine origin for growth, or more specifically
they need to be supplied with long chain ω3 fatty acids such as DHA (22:6 ω3,
docosahexaenoic acid) and EPA (20:5 ω3, eicosapentaenoic acid). Such highly
unsaturated ω3 fatty acids (ω3HUFA) are only present in high amounts in marine
or aquatic organisms. Mariculture of marine organisms can therefore not easily be
based on lipids from agriculture, because the essential fatty acid composition is
different. Oils from higher plants are typically rich in ω6 fatty acids and short chain
ω3 fatty acids (e.g., 18:3 ω3, α-linoleic acid). This fact represents a major potential
constraint for developing mariculture during the next century, because the feed
resources in mariculture are not as easily available as the feed resources in agriculture (plants). Mariculture feed for most type of organisms is based on herbivore
animals that are harvested from wild stocks. It is therefore not obvious that mariculture
will become as successful as agriculture, because such wild stocks have a limited
availability (e.g., Myers and Worm 2003).
There are some potential ways to provide new marine fatty acids rich resources
for fish feed. An ultimate challenge is to reduce discards from fisheries; some 20
million tonnes year
−1 might then become available (Hall and Mainprize 2005).
Other options are:
●
Selected suitable oils (and protein) from agriculture – these resources can be
used to dilute the marine resources, but cannot replace them entirely.
●
“New” marine resources – a significant increased harvesting of resources can
only be achieved by harvesting at low trophic levels of the marine food web,
emphasizing the use of marine plants and herbivore invertebrates.
●
Production of “single cell biomass” using microorganisms with marine-type lipids,
ω3 HUFA rich.
●
Production of genetically modified organism (GMO) with marine-type lipids –
e.g., a transgenic microorganism (“single cell biomass”) or a higher plant with
ω3 HUFA genes transferred from algae
Use of resources produced in agriculture for mariculture will not contribute essentially to the world supply of food, and these conflicts are more easily seen from a
densely populated region as SE Asia than from western countries, where the general