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Y. Olsen et al.
competence and technical skills. Flow-through fish farms is still most common.
Land based farms can be seen as a development of pond cultures that are organized
and operated to allow intensification under adequate production control. One of the
main differences between recycling systems and cage cultures is that the physical
environmental conditions can be fully controlled in RAS. For instance, temperature and
light cannot be directly controlled with cages. Manipulation of the growth environment can help reduce production time in RAS systems, through, for instance, the
control of temperature around optimal levels. These improvements can compensate
for the higher capital and maintenance costs of land-based farms as compared to
cage cultures.
It is also important to note that RAS, contrary to cage systems, allows a better
control of waste emissions. The particulate sludge can be used to produce other
organisms or it can be collected and deposited on land. Dissolved nutrients can be
retained in appropriate biofilters. It is in principle possible to reuse waste products
from cage cultures as well, but this cannot be done in the same controlled way.
Combining the cultivation of species of different trophic levels, through the development of integrated multi-trophic aquaculture (IMTA) systems, allows waste
recycling for cage cultures. Mussels capture particulate wastes, fish faeces and feed
particles downstream of the farm. Seaweeds and phytoplankton absorb inorganic
nutrients, and the enhanced phytoplankton growth downstream of the cage system
supports mussel production (Neori et al. 2004).
10.5.4 Main Lines of Technological Development
Environmental concern and legislation, along with the reduced available space in
coastal zone, will most likely be the main drivers for future innovations and developments of mariculture technology. In the western world, these drivers are anticipated to steer mariculture technology along two main lines of developments:
●
Cage culture for fish and long-line culture for mussels and seaweeds will move
gradually away from the shoreline, towards the open ocean (ultimately offshore
mariculture)
●
Land-coastal based fish farms, with reuse of water and control of waste emission.
The capacity to produce marine fish in open-ocean conditions is very high, although
it can be risky, under strong hydrodynamic conditions, where wastes from the fish
farms will be diluted very efficiently (Olsen et al. 2005). It is very likely that
dynamic water conditions are beneficial for fish welfare; at least it is associated
with high feed conversion efficiency for salmon. Last, but perhaps most important,
is the fact that the big modern cage farms are very cost efficient. Mussels and
seaweeds can grow fast in open ocean sites, but the availability of wastes and excess
nutrients released from the cage fish farm will be low. More closed and less
dynamic locations are therefore better suited for IMTA.
Land based RAS is another compromise to mitigate environmental concern and
space requirements, but land based farms will normally have higher production
Y. Olsen et al.
competence and technical skills. Flow-through fish farms is still most common.
Land based farms can be seen as a development of pond cultures that are organized
and operated to allow intensification under adequate production control. One of the
main differences between recycling systems and cage cultures is that the physical
environmental conditions can be fully controlled in RAS. For instance, temperature and
light cannot be directly controlled with cages. Manipulation of the growth environment can help reduce production time in RAS systems, through, for instance, the
control of temperature around optimal levels. These improvements can compensate
for the higher capital and maintenance costs of land-based farms as compared to
cage cultures.
It is also important to note that RAS, contrary to cage systems, allows a better
control of waste emissions. The particulate sludge can be used to produce other
organisms or it can be collected and deposited on land. Dissolved nutrients can be
retained in appropriate biofilters. It is in principle possible to reuse waste products
from cage cultures as well, but this cannot be done in the same controlled way.
Combining the cultivation of species of different trophic levels, through the development of integrated multi-trophic aquaculture (IMTA) systems, allows waste
recycling for cage cultures. Mussels capture particulate wastes, fish faeces and feed
particles downstream of the farm. Seaweeds and phytoplankton absorb inorganic
nutrients, and the enhanced phytoplankton growth downstream of the cage system
supports mussel production (Neori et al. 2004).
10.5.4 Main Lines of Technological Development
Environmental concern and legislation, along with the reduced available space in
coastal zone, will most likely be the main drivers for future innovations and developments of mariculture technology. In the western world, these drivers are anticipated to steer mariculture technology along two main lines of developments:
●
Cage culture for fish and long-line culture for mussels and seaweeds will move
gradually away from the shoreline, towards the open ocean (ultimately offshore
mariculture)
●
Land-coastal based fish farms, with reuse of water and control of waste emission.
The capacity to produce marine fish in open-ocean conditions is very high, although
it can be risky, under strong hydrodynamic conditions, where wastes from the fish
farms will be diluted very efficiently (Olsen et al. 2005). It is very likely that
dynamic water conditions are beneficial for fish welfare; at least it is associated
with high feed conversion efficiency for salmon. Last, but perhaps most important,
is the fact that the big modern cage farms are very cost efficient. Mussels and
seaweeds can grow fast in open ocean sites, but the availability of wastes and excess
nutrients released from the cage fish farm will be low. More closed and less
dynamic locations are therefore better suited for IMTA.
Land based RAS is another compromise to mitigate environmental concern and
space requirements, but land based farms will normally have higher production