Fish farming may be a way to reduce harmful impacts on aquatic ecosystems that occur during large-scale fishing operations.
But fish farming also has its own drawbacks. Home-scale fish-farming techniques have been honed and non-carnivorous fish, such as tilapia, are rapidly becoming a popular choice for fish farmers.
Extensive vs. Intensive
The two types of fish farming (or “pisciculture”), are the “extensive” model and the “intensive.” The extensive model involves raising populations in semi-natural ponds and relying on photosynthetical food production to feed fish. The idea is to cultivate a simplified ecosystem. Zooplankton feed on aquatic plants and, with mollusks and crustaceans, provide food for farmed fish. Adjuncts that stimulate photosnythetic life are used. The major drawback to this system are algal blooms, which occur rapidly when conditions permit. This essentially suffocates life in the habitat.
The intensive model uses tanks and a higher degree of inputs to exact greater control over the growing environment. Aerated, filtered water and sufficient protein-rich feed must be kept in supply to maintain fish populations. This model is the most common for small-scale pisciculture operations, as there are some novel work-arounds for common problems.
The most common fish species to be farmed are salmon, tilapia, carp, catfish and cod, due to their desirous taste among humans.
All the problems of maintaining a contained, artificial environment are present in pisciculture. Parasites, such as sea lice can be difficult to eradicate.
Also, while non-carnivorous fish are relatively easy to maintain, carnivorous fish, such as salmon must be fed a diet that consists of meal and oil of anchovies and menhaden, an Altlantic fish species which is rapidly being decimated to produce commercial fish oils that have boomed in popularity in recent years.
More controversial still are slaughter methods. A previously-popular method was suffocation by pumping carbon-dioxide into water, rendering fish unconscious. Their gills were then cut to finally kill them. Open-air asphyxiation has been used, as have submerging fish in ice baths, with the idea being to delay the onset of post-mortem decay. It does not, however, desensitize the fish from feeling pain. It merely stuns their muscles. This method, among many others, produce high levels of pain and distress for the fish. Stunning, either percussively or with electricity, are coming into wider practice, as some methods are being phased out.
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For those wishing to implement a pisciculture system at home, there are several systems one could link together, harnessing the feedbacks of what Permaculturalists would call various “elements.” One could, theoretically position a rabbit hutch to eject manure into a small extensive pond, feeding nitrogen into the pond where photosynthetic aquatic life would harness it.
You could also use hydroponic horticulture to purify and aerate pisciculture fish tanks, linking the two systems together.
An intensive process was created by the New Alchemy Institute of Massachusetts in the 1970′s. Translucent fish tanks are regulated by solar energy concentrated in a greenhouse. The waste-water from this system is used to irrigate crops. The New Alchemy system is incredibly efficient and could be adopted at a small farm.
The fish farming model offer real alternatives to large scale fishing operations. Still, ambiguity surrounds many seafood meals. While a fish farm implies that our oceans and streams are not being raided for your meal, depending on the fish farming techniques used, you may still have some other ethical concerns of your ow