The worldwide yearly catch of all sea fish is between 60 and 80 million tonnes. There are around 20,000 species of fish, of which 9,000 are regularly caught, but only 22 species are taken in large amounts. Five groups of fish make up half the yearly catch: herrings, cod, jacks, redfish and mackerel.

Commercial fishing of the oceans has decimated both fish stocks and the aquatic environment. Modern fishing fleets use a variety of techniques to catch fish including drift net, bottom trawls and purse seine nets. All 17 of the world's major fisheries have either reached or exceeded their limits.

More than 10 years after its closure, Canada's Atlantic Cod fishery shows virtually no signs of recovery in 2003. The implication is that it may be too late to save Europe's cod stocks. Persistant overfishing in Newfoundland led to a crash in stocks to just a few per cent of long term averages. Fishing was stopped in 1992, with expectation of recovery taking 5-10 years. But depleted stocks have barely increased at all because the young stock is not as productive and is more vulnerable to predators. Another problem is that the fishers were retrained in electronics - which has been put to use to increase fishing efficiency, taking most of the little increase in stock!

The farming of fish, known as aquaculture, is promoted as the answer to fish production. More than 220 species of fish and shellfish are cultivated commercially. Farmed fish and shellfish supply 30% of all the seafood consumed worldwide today, up from 10% two decades ago.

The rearing of large numbers of fish in confined areas leads to high incidence of diseases, including bacterial gill disease. Sea lice infecting farm salmon increase the incidence among wild salmon. Many fish die before slaughter. In addition to aggressive behaviour, grading and disease, fish die from toxic algal blooms and oxygen starvation in hot weather.

The high level of disease has led to a heavy reliance on the drug industry for antibiotics, which are routinely administered in the feed. Other chemicals are used for a variety of reasons, including colour pigments to make farmed salmon look more natural.

Farmed salmon require an equal weight of landed fish for each tonne of salmon produced (plus 4 tonnes of "waste" fish, usually in a mix called of 'industrial meal') ). This adds more pressure to the oceans' fish stocks. US scientists examined 700 salmon from 8 regions of the world and found that Scottish (with Faroe Island) farmed salmon were the most contaminated for all 14 organochlorines tested. The researchers recommend that these salmon be eaten only once every two months to protect against increasing the risk of cancer. UK and EU authorities say that the amounts are within acceptable levels. Latest from Salmon Farm Monitor

Shrimp are often produced in areas cleared of mangrove forests causing a decline in local fisheries and like salmon need a diet of fishmeal resulting in a net loss of fish.

Fish grown in offshore cages and pens produce large concentrations of waste. Farmed salmon in Norway produce approximately the same quantity of waste as the total sewage produced by Norway's 4 million people.