The global appetite for fish has doubles over the last thirty years. But because of depletion of the world stock, virtually all the growth in the catch today comes not from the ocean but from fish raised on farms, or aquaculture.
As the demand for fish skyrockets, producers are adapting more intensive, industrial style methods, which can cause the same sorts of problems as those on land.
Farmed salmon, for example, spend the 2 – 3 years of their lives crammed into pens, where there are fed high protein fish meal. This practice of giving farmed fish the ground up bits of other marine species results in a net loss to world fish protection: according to a study, for ten types of fish commonly farmed on average of 1.9 kilograms of wild fish is required for every kilogram of farmed fish.There is a proposing the next phase of fish farming open ocean aquaculture, or the constriction of penned farms for large carnivores fish fattened with fish meal, located more than 300 kilometers offshore.
As with livestock, farmed fish often contain a range of unexpected ingredients. They require massive doses of antibiotics and pesticides to prevent diseases that result from overcrowding , including sea lice, a parasite that can spread quickly in crowded pens.
Aquaculture includes in-shore systems of clams, oysters and other mollusks, which are wild caught or hatchery reared seed grown on the sea floor or in suspended nets, ropes or other structures.
Offshore aquaculture often refers to large intensive fisheries in offshore fish pens. Aquaculture systems targeting low trophic level species such as carp, tilapia, catfish and mollusks which occupy a low position in the predator-prey food chain can be much more sustainable than systems targeting higher trophic level species such as salmon, tune, or cod.
In this system. the pens are large net bag, made of nylon thread, suspended in the water. At the surface, they are held down by weights.
There is a fence at the top, around the flotation unit , to stop the fish from jumping put.
To keep the pens in place, they are anchored to the seabed. The pens are often round. This makes them flexible and easy to move.
Offshore Fish Farming
