A factory ship, also known as a fish processing vessel, is a large ocean-going vessel with extensive on-board facilities for processing and freezing caught fish. According to the FAO, there are about 38,400 vessels greater than 100 tons in the world's factory fishing fleet.
Contemporary factory ships are automated and enlarged versions of these earlier whalers. Their use for fishing has grown dramatically. For a while, Russia, Japan and Korea operated huge fishing fleets centred on factory ships, though in recent times this use has been declining. On the other hand, the use of factory ships by the United States has increased.
Some factory ships can also function as mother ships. The basic idea of a mother ship is that it can carry small fishing boats that return to the mother ship with their catch. But the idea extends to include factory trawlers supporting a fleet of smaller catching vessels that are not carried on board. They serve as the main ship in a fleet operating in waters a great distance from their home ports.
A freezer trawler fully processes the catch on board to customers’ specifications, into frozen-at-sea fillet, block or head and gutted form. Factory freezer trawlers can run to 60 to 70 meters in length and go to sea for six weeks at a time with a crew of over 35 people. They process fish into fillets within hours of being caught. Onboard fishmeal plants process the waste product so everything is utilized.
A purse seiner is a fishing vessel which uses a traditional method of catching tuna and other school fish species. A large net is set in a circle around a school of fish while on the surface. The net is then pursed, closing the bottom of the net, then pulling up the net until the fish are caught alongside the vessel. Most of these types of vessels then transfer the fish into a tank filled with brine (extra salty refrigerated water). This freezes large amounts of fish quickly. Trip lengths can vary from 20 to 70 days depending on the fishing. The fish is held in refrigerated brine tanks and unloads either directly to the canneries or is trans-shipped to carrier vessels to freight to the canneries, leaving the purse seine vessel close to the fishing grounds to continue fishing. Purse seiners longer than 70 metres are called super seiners.
Commercial fish processing ships can affect birds, whales, dolphins, turtles and sharks by their broad reach methods of catching fish.
A major international scientific study released in November 2006 in the journal Science found that about one-third of all fishing stocks worldwide have collapsed (with a collapse being defined as a decline to less than 10% of their maximum observed abundance), and that if current trends continue all fish stocks worldwide will collapse within fifty years.
The FAO State of World Fisheries and Aquaculture 2004 report estimates that in 2003, of the main fish stocks or groups of resources for which assessment information is available, "approximately one-quarter were overexploited, depleted or recovering from depletion (16%, 7% and 1% respectively) and needed rebuilding.
The threat of overfishing is not limited to the target species only. As trawlers resort to deeper and deeper waters to fill their nets, they have begun to threaten delicate deep-sea ecosystems and the fish that inhabit them, such as the coelacanth. In the May 15, 2003 issue of the journal Nature, it is estimated that 10% of large predatory fish remain compared to levels before commercial fishing. Many fisheries experts, however, consider this claim to be exaggerated with respect to tuna populations.
From 1950 (18 million tons) to 1969 (56 million tons) fishfood production grew by about 5% each year; from 1969 onward production has raised 8% annually. It is expected that this demand will continue to rise, and MariCulture Systems estimated in 2002 that, by 2010, seafood production would have to increase by over 15.5 million tonnes to meet the desire of Earth's growing population. This is likely to further aggravate the problem of overfishing, unless aquaculture technology expands to meet the needs of human population.
Overfishing has depleted fish populations to the point that large scale commercial fishing, on average around the world, is not economically viable without government assistance, However EU law prohibits subsidies to fleets of its member states.