232
K. Bostick
1980s (Hansen et al. 2006). Escaped farmed fish are of particular concern in areas
where there are sensitive wild endangered fish populations.
Diseases can be both introduced and transmitted through aquaculture. Without
proper controls and quarantines, it is possible for diseases or parasites to be introduced to a region through the importation of juveniles. In cases of disease outbreak
on a farm, the disease can be transmitted to the wild if it is an open production system or if contaminated water from a closed system is released into the environment.
Just as pathogens and parasites can be transferred from farms into the wild, disease
free farmed species can be infected from the wild and in open production systems
there is flow in both directions. Diseases can also be transmitted from farm to farm,
and the shrimp industry in certain parts of the world has collapsed due to severe
disease outbreaks. Disease introduction and transfer can also be a concern in shellfish and seaweed culture systems (Boyd et al. 2005).
Other key farm-level impacts that concern many environmental NGOs are land
conversion and predator control. The construction of shrimp ponds has been linked
with the conversion of hundreds of thousands of hectares of coastal mangrove
forests (Naylor et al. 2000). Though it appears that this trend has decreased significantly, NGOs remain concerned with the loss of these forests because they provide
a wide range of important ecosystem services as well as economic benefits to
coastal communities. In inland, coastal, and ocean production systems, predator
control is another issue of concern to some NGOs, especially in cases where the
wild predating species is endangered. Birds, seals, and sharks are among the species that are drawn to aquaculture ponds or pens in search food. Lethal control of
these species is sometimes used by producers to protect their farmed stocks. As
with many of these farm-level impacts, the impact of one farm on the environment
may be relatively small. Yet when there are a number of farms in a region, impacts
accumulate to a level where they are of considerable concern.
The impact of fish farms extends beyond a local or regional level. NGOs commonly hold that aquaculture should produce more protein than it consumes. On a
global scale, aquaculture relies on high-protein, fishmeal and fish oil-based feed for
carnivorous species that often requires multiple kilograms (kg) of wild fish to produce one kg of edible aquaculture product (Tacon 2005). Although the production
of omnivorous or vegetarian fish such as tilapia and carp can result in a net increase
in fish protein, they are also often fed a small percentage of fishmeal and fish oil in
their diets. This can be cumulatively significant for species that are produced in
large volumes. Given the tenuous state of global pelagic fisheries, environmental
NGOs are concerned that increased pressure on and demand for these fisheries will
lead to their collapse. The overfishing of small pelagic fish affects species up the
marine food web because they are critical components of the diets of marine mammals, seabirds, and large carnivorous fish species (Naylor et al. 2000). By way of
example, sandeel stocks in the North Sea are depleted which has been demonstrated
to have detrimental effects on seabird populations such as the sandwich tern (ICES
2006). Most of the species reduced into fishmeal and fish oil for aquaculture feeds
are also consumed directly by humans. Some NGOs are also concerned that the use
of these pelagic fish for aquaculture, and any consequent collapse in fisheries, could
have significant impacts on poor communities that rely on this protein source.
K. Bostick
1980s (Hansen et al. 2006). Escaped farmed fish are of particular concern in areas
where there are sensitive wild endangered fish populations.
Diseases can be both introduced and transmitted through aquaculture. Without
proper controls and quarantines, it is possible for diseases or parasites to be introduced to a region through the importation of juveniles. In cases of disease outbreak
on a farm, the disease can be transmitted to the wild if it is an open production system or if contaminated water from a closed system is released into the environment.
Just as pathogens and parasites can be transferred from farms into the wild, disease
free farmed species can be infected from the wild and in open production systems
there is flow in both directions. Diseases can also be transmitted from farm to farm,
and the shrimp industry in certain parts of the world has collapsed due to severe
disease outbreaks. Disease introduction and transfer can also be a concern in shellfish and seaweed culture systems (Boyd et al. 2005).
Other key farm-level impacts that concern many environmental NGOs are land
conversion and predator control. The construction of shrimp ponds has been linked
with the conversion of hundreds of thousands of hectares of coastal mangrove
forests (Naylor et al. 2000). Though it appears that this trend has decreased significantly, NGOs remain concerned with the loss of these forests because they provide
a wide range of important ecosystem services as well as economic benefits to
coastal communities. In inland, coastal, and ocean production systems, predator
control is another issue of concern to some NGOs, especially in cases where the
wild predating species is endangered. Birds, seals, and sharks are among the species that are drawn to aquaculture ponds or pens in search food. Lethal control of
these species is sometimes used by producers to protect their farmed stocks. As
with many of these farm-level impacts, the impact of one farm on the environment
may be relatively small. Yet when there are a number of farms in a region, impacts
accumulate to a level where they are of considerable concern.
The impact of fish farms extends beyond a local or regional level. NGOs commonly hold that aquaculture should produce more protein than it consumes. On a
global scale, aquaculture relies on high-protein, fishmeal and fish oil-based feed for
carnivorous species that often requires multiple kilograms (kg) of wild fish to produce one kg of edible aquaculture product (Tacon 2005). Although the production
of omnivorous or vegetarian fish such as tilapia and carp can result in a net increase
in fish protein, they are also often fed a small percentage of fishmeal and fish oil in
their diets. This can be cumulatively significant for species that are produced in
large volumes. Given the tenuous state of global pelagic fisheries, environmental
NGOs are concerned that increased pressure on and demand for these fisheries will
lead to their collapse. The overfishing of small pelagic fish affects species up the
marine food web because they are critical components of the diets of marine mammals, seabirds, and large carnivorous fish species (Naylor et al. 2000). By way of
example, sandeel stocks in the North Sea are depleted which has been demonstrated
to have detrimental effects on seabird populations such as the sandwich tern (ICES
2006). Most of the species reduced into fishmeal and fish oil for aquaculture feeds
are also consumed directly by humans. Some NGOs are also concerned that the use
of these pelagic fish for aquaculture, and any consequent collapse in fisheries, could
have significant impacts on poor communities that rely on this protein source.