The fishing industry includes any activity involved in the catching, culturing, processing, preserving, storing, transporting, marketing or selling of fish or fish products.

Since the beginning of time hunter-gatherers recognised fish as a good nutritious source of food and with the gradual development of trade a fishing industry began to establish itself.

In the Middle Ages a fish pond would be a common feature of every monastery and coastal areas saw the growth of a small and localised industry, but in pre-refrigeration days it was not until the growth of the railway network that sea fish could be brought to inland populations for the first time. The expanding towns of the industrial revolution provided a ready market.

In these days of swift global transport, coupled with developments in the freezing and preservation of food, large quantities of fish are eaten in many countries around the world. Directly or indirectly fishing provides a livelihood for over 500 million people in the world's developing countries.

A commercial fishing enterprise can range from one man with a small boat and a hand casting net or a few pot traps to a fleet of trawlers or a factory ship. Fishing can now be very big business. Large-scale commercial fishing is now truly industrial fishing.

The UN Food and Agriculture Organisation (FAO) reported that in 2005 93.3 million tonnes of fish was landed as a result of commercial fishing in wild fisheries, with a further 48.1 million tonnes produced by fish farms.

China is the world's number one fish consumer and has the world's largest fishing industry, accounting for a third of the world's catch. This is followed in order by Peru, Japan, the US, Chile, Indonesia, Russia, India, Thailand, Norway and Iceland. Together these countries account for more than half of the total amount caught.

Although Peru is number two in the world for catching fish, Peruvians eat hardly any of this and it is exported. On the other hand, fish is so popular in Japan that although at number two in the catching list, Japan has to buy as much again from other countries in order to meet the domestic demand.

Fishing methods will vary according to the region, the species being fished for and the technology available to the fishermen. There are large and important fisheries worldwide for various species of fish, molluscs, crustations and echinoderms, but a very small number of species support the majority of the world's fisheries. The most popular are herring, cod, anchovy, tuna, flounder, mullet, squid and salmon.

Traditionally 99% of the worldwide annual commercial ocean catch has come from coastal waters, within 200 nautical miles of the coastline, but while these narrow coastal fringes are both the most productive they are also the most vulnerable.

In an effort to conserve stocks, fishing quotas have been introduced. These restrict the numbers of particular species that can be landed. Unfortunately this does not restrict the numbers that are caught and fish that are on the restricted list have to be thrown back into the sea, by which time they are usually dead.

Overfishing has resulted in marine fish stocks being depleted, overexploited or at their biological limit. In the commercial fishing areas between North America and the British Isles, there has been a 90% decline in predatory fish populations, notably cod.

The simple reason for this is that the fish population has not been able to regenerate itself quickly enough to replace the fish that have been caught.

This has done nothing to reduce the incessant demand, worldwide, for more fish. The result is bigger and more efficient ocean-going ships that are effectively floating factories with extensive on-board facilities to process and freeze caught fish. According to FAO there are now approaching 40,000 vessels greater than 100 tons in the world's factory fishing fleet.

Contemporary factory ships are highly automated and can operate at great distances from their home ports. Sometimes they act as mother ships that can support a fleet of smaller catching vessels.

There are various types of these fish processing ships, including stern trawlers, freezer trawlers, longline factory vessels, purse seine freezer vessels, and squid jiggers. All are highly efficient, but all fish in a slightly different way.

Stern trawlers can stay at sea for weeks at a time. They pull a fishing trawl net behind them and pull the catch up a stern ramp. They have onboard processing facilities and can also operate in pairs towing a huge net with a mouth 900 metres in circumference.

Freezer trawlers will fully process the catch on board to the specifications of the customer. They will have a crew of over 35 people and can stay at sea for six weeks at a time. Fish will be processed within hours of being caught and since trawling is completely indiscriminate, all of the unwanted fish is processed into fishmeal for animal feed.

The world's largest freezing trawler is 144 metres long and is able to process 350 tonnes of fish each day with a capacity to store 7,000 tonnes of frozen processed catch.

Longline factory vessels, as their name suggests, use hooks strung on long lines. The hooks are baited automatically and many thousands are set each day. The setting and retrieving of hooks is a 24-hour operation and again, the ships will stay at sea for six weeks at a time and the fish will be processed within hours and packaged up ready for the market.

A purse seiner is used to catch tuna and other school fish species. Again it is very efficient, with a large net being set around a school of fish that are close to the surface. These nets can be up to two kilometres in circumference and will trap everything.

The net is then pursed, closing the bottom and pulling it in so that the fish are caught alongside the vessel. The usual procedure is then to transfer the fish into a tank filled with extra salty refrigerated water that freezes large numbers of fish very quickly. The fish are held in the tanks and taken directly to the cannery, or transhipped into carrier vessels leaving the purse seine to carry on fishing.

The factory squid jiggers use powerful lights to attract squid and then 'jig' many thousands of hooked lures from hundreds of separate winches. Most of these ships are Japanese or Korean and their crews will stay at sea for as long as two years at a time. Periodically the processed squid is transferred to larger refrigerated vessels.

Understandably fishing in this concentrated, highly efficient, but completely indiscriminate way can have a disastrous effect on the ecological balance of a region. Birds, whales, dolphins, turtles and sharks are all just as likely to be caught up in the process as the fish that are being sought. In the trade this is simply known as "bycatch".

The effects of overfishing on the ecological balance can be dramatically illustrated by the reduction of the numbers of herring in various parts of the world. Herring are an important food-source for cod and since cod is also on the danger list, the loss of an important element in its food chain makes it even harder for it to recover.

Other species are also showing a marked decline in numbers as their food supply becomes increasingly threatened.

As stocks of fish get smaller and harder to find, trawlers are resorting to deeper and deeper waters to fill their nets. The point has now been reached where ecosystems are becoming seriously threatened as deep-water trawl nets scrape everything off the bottom of the ocean, destroying everything in their path.

Shark Finning: A soaring worldwide demand for shark fins is putting at least one third of the world's deep-sea sharks in danger of extinction. In Asia shark-fin soup is said to be good for your virility and it is held in high regard as a status symbol at weddings and other celebrations. An estimated 10.7 million blue sharks alone are killed each year for their fins. Some populations of hammerhead sharks have declined as much as 99% in heavily fished regions and although demand for shark meat is "strong" in Europe, for the Far Eastern market the fins are all that are required. After finning the carcass is often dumped back into the sea.

Dolphin drive hunting is a method of hunting dolphins by driving them together with boats and then usually into a bay or onto a beach. They are then dragged out of the water and butchered, often in a very brutal fashion. Small whales are also hunted in the same way. This is a traditional way of hunting in the Faeroe Islands and in Japan. The Japanese town of Taiji on the Kii peninsular is the only town where dolphin drive hunting is now said to take place. Although officially the annual number of animals killed is less than 100, conservation activists put the true number at several thousand. The method of killing is very cruel and a film The Cove analysed, exposed and questioned this method of hunting in Japan. The film won the 2010 Academy Award for the best documentary film.

According to the United Nations, over 70% of the world's fisheries are either "fully exploited", "over exploited" or "significantly depleted".

The journal Science released a major scientific study in November 2006 which said that about one third of all fishing stocks worldwide had reached a point where they were less than 10% of their maximum observed abundance. In other words they had effectively collapsed. The report prophesied that if the current trend continued, all fish stocks worldwide would collapse within fifty years.

The sad fact is that the point is rapidly being reached where commercial fishing from wild fisheries is fast ceasing to be viable. Perhaps the only hope for future supply is the expansion of fish farming.

Currently about a third of all the fish eaten in the United States comes from fish farms, but fish farming is not without its problems. Salmon, for instance, are very commonly farmed and global farmed salmon production exceeds a million tonnes a year. However, to feed this number of salmon requires the catching and processing of between 2 and 3 million tonnes of wild fish.

An average salmon farm has around 200,000 fish and inevitably some will escape, where they can have a significant impact on the surrounding ecosystem as they compete for food with wild salmon and spread diseases that did not previously exist in wild fish populations. In addition, farmed fish are often genetically modified and may interbreed with the wild fish and alter the natural genetic makeup of that species.

Furthermore, 200,000 salmon produce the daily equivalent amount of faeces as a town of 62,000 people. This waste sinks to the sea bed and generates killer bacteria that consume the oxygen vital to wild bottom fish.

The oceans of the world have always been rich in their ecological diversity and since the beginning of time they have been a bountiful supplier of nutritious food. Now, due largely to a mixture of greed and lack of foresight, the future is beginning to look very bleak.

The hope is that if given a chance, the oceans of the world might eventually recover from the ecological harm that has been done to them, but unless something can be done to stop overfishing and habitat destruction, the point will be reached where recovery is no longer possible.