Original links are included though some may have expired.

The Numbers:

Tons of ocean fish caught, 1950: 20 million
Tons of ocean fish caught, 2003: 81 million

What They Mean:

The sad story of the Grand Banks cod fishery is a warning about ocean fisheries generally. English mariner Edward Haye, sailing toward Newfoundland in 1583 -- 25 years before the Pilgrims landed at Plymouth -- was astonished to see a city of ships, shadowed by a huge flock of terns and gulfs, floating 150 miles off the coast:

"The Portuguese and French have a notable trade of fishing upon this Bank, where there are sometime a hundred or more sail of ships, who commonly begin the fishing in April, and have ended by July. During the time of fishing, a man shall know without sounding [testing depth] when he is upon the Bank, by the incredible multitude of sea fowl hovering over the same, to prey upon the offals and garbage of fish thrown out by fishermen and floating upon the ocean."

Familiar for centuries, such sights are now gone. Between 1970 and 1990, factory ships took most of the Bank's cod and flounder. Newfoundland's cod catch, at about half a million tons a year in the 1980s, is now limited to 20 or 30 million tons a year. Worldwide, meanwhile, the global fishing fleet, including 24,400 large decked ships and well over 2 million smaller commercial craft, pulls 80 million tons of fish or more from the oceans, or four times the 1950 total. Another 9 million tons of fish come from lakes and rivers. Fish of course spawn and recover when they get the chance, but overfishing can permanently change fishing grounds and populations. The Pew Ocean Commission found three years ago that the count of big predatory fish is down by 90 percent since the 1950s; and periodic reports by NOAA and the United Nation's Food and Agriculture Organization say that a quarter of the world's fishing grounds have been so heavily trawled that they may be unable to recover for decades.

Three reasons for guarded optimism exist. One is fish farming, or "aquaculture." Shrimp ponds, salmon pens, sturgeon tanks, planted oyster- and abalone-beds now produce over 40 million tons of seafood each year -- nearly a third of the annual 132 million tons of fish consumption -- and account for a quarter of the world's 50 million tons of seafood exports. Another reason is the reduction of the annual $14 billion to $20 billion subsidies in fishery industries through a WTO agreement; but this, like the rest of the "Doha Round," is in limbo. Third, the FAO finds international efforts to reduce "bycatch" cutting the accidental catch of unwanted fish, cephalopods, marine mammals, turtles and birds from as much as 15 million to perhaps 7.3 million tons a year; it cites fisheries in Alaska, the Gulf of Mexico, Australia, Canada, Iceland, Namibia, and Norway as especially successful.

Further Reading:

A bit on eating habits -- Americans now eat 7 kilos of fish a year, up from 4 kilos in 1960. Japanese eat 50 kilos annually -- the equivalent of six out of the total 132 million tons of world fish consumption. Even the Japanese are modest in comparison to the people of the Maldives Islands, reported by FAO to eat 180 kilos of fish a year, or the equivalent of two one-pound fishes a day.

FAO's State of World Fisheries 2004:
http://www.fao.org/DOCREP/007/y5600e/y5600e00.htm

NOAA's most recent comprehensive report, Fisheries of the United States 2004:
http://www.st.nmfs.gov/st1/fus/fus04/index.html

How many fish in the sea? The ocean catch totals 80-85 million tons a year. Out of what total? Nobody is quite sure. The Census of Marine Life hopes to use sonar to get a rough count of the fish.
http://www.coml.org/medres/mit/MIT_News_Release.pdf

The World Wildlife Fund's fisheries page explains subsidies:
http://www.panda.org/about_wwf/what_we_do/
marine/index.cfm

The Los Angeles Times reports on abalone-farming around San Francisco:
http://www.abalonefarm.com/abfarm_latimes.pdf

Tokyo's Tsukiji, the world's largest fish market, sells 2,900 tons a day:
http://www.tsukiji-market.or.jp/youkoso/welcom_e.htm

Namibia's Ministry of Fisheries and Marine Resources, developing-country model for bycatch reduction:
http://www.mfmr.gov.na/

Three views of the Grand Banks:

Edward Haye's 1583 report, in Richard Hakluyt's Voyages and Navigations, is available at the Gutenberg project but not easy to read:
http://www.gutenberg.org/etext/13605

Newfoundland's Department of Education recounts the history and collapse of the northern cod fishery:
http://www.stemnet.nf.ca/cod/home1.htm

And Newfoundland's Fisheries and Aquaculture Ministry brings it up to date, along with a link to Canada's national fishery ministry:
http://www.fishaq.gov.nl.ca/