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Secondary production is the use of energy stored in plants converted by consumers to their own biomass. Different ecosystems have different levels of consumers, all end with one top consumer. Most energy is stored in organic matter of plants, and as the consumers eat these plants they take up this energy.
Fish farming or pisciculture involves commercial breeding of fish, most often for food, in fish tanks or artificial enclosures such as fish ponds. It is a particular type of aquaculture , which is the controlled cultivation and harvesting of aquatic animals such as fish, crustaceans , molluscs and so on, in natural or pseudo-natural environments.
[3] [4] The average depth of a raceway for fin fish, such as rainbow trout, is about one metre. [17] This means each section in a raceway should be about 30 m long and 2.5–3 m wide. The landscape should sloped to one or two percent, so the flow through the system can be maintained by gravity.
It covers 11.4 million square kilometres (4.38 million sq mi), which is the second largest zone in the world, exceeding the land area of the United States. [5] According to the FAO, in 2005, the United States harvested 4,888,621 tonnes of fish from wild fisheries, and another 471,958 tonnes from aquaculture. This made the United States the ...
Another impact aquaculture production can have on wild fish is the risk of fish escaping from coastal pens, where they can interbreed with their wild counterparts, diluting wild genetic stocks. [109] Escaped fish can become invasive , out-competing native species.
The efficiency with which energy or biomass is transferred from one trophic level to the next is called the ecological efficiency. Consumers at each level convert on average only about 10% of the chemical energy in their food to their own organic tissue (the ten-per cent law). For this reason, food chains rarely extend for more than 5 or 6 levels.
Out of a total of 28,400 terawatt-hours (96.8 × 10 ^ 15 BTU) of energy used in the US in 1999, 10.5% was used in food production, [3] with the percentage accounting for food from both producer and primary consumer trophic levels. In comparing the cultivation of animals versus plants, there is a clear difference in magnitude of energy efficiency.
Organisms that rely on light energy to fix carbon, and thus participate in primary production, are referred to as photoautotrophs. [6] Photoautotrophs exists across the tree of life. Many bacterial taxa are known to be photoautotrophic such as cyanobacteria [7] and some Pseudomonadota (formerly proteobacteria). [8]