Modern factory ships are automated and enlarged versions of the earlier whalers, and 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.

But the idea extends to include factory trawlers supporting a fleet of smaller catching vessels that are not carried on board.

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.

In 2015, the Annelies Ilena was detained by the Irish Navy and the Sea Fisheries Protection Agency for breach of regulations.

Most of these types of vessels then transfer the fish into a tank filled with brine (extra salty refrigerated water).

[2] The 8,145-ton MV Nisshin Maru was the mothership of the Japanese whaling fleet and was the world's only remaining whaler factory ship[3] until its decommissioning in 2023.

The ship is owned by Tokyo-based company Kyodo Senpaku Kaisha Ltd. and is contracted by the Japanese Institute of Cetacean Research.

Purse seine ships, with nets up to two kilometres in circumference, can encircle whole shoals of pelagic fish, such as mackerel, herring and tuna.

[10] 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.

According to Oceana, the global fishing fleet is currently up to 250 percent larger than it needs to be to catch what the oceans can sustainably produce.