A new study (here is the abstract) has found that the quantity of large fishes weighing 4-16kg in the North Sea has declined by 97% since the onset of fishing. For bigger fish (16-66kg) that percentage is 99%. Pretty shocking numbers I think you'll agree. Perhaps even more remarkably, the total amount of fish (expressed by weight), including all species, ages, and sizes, has dropped by nearly 40% since fishing started. That's more than a third of the fish in the North Sea.
No wonder it's so difficult to get fish and chips made with cod anymore - pop into a British 'chippy' and you'll likely get dogfish in batter. At least that's still a fish I guess (though it's a closer relative to sharks than bony fishes like cod, bass and herring). Perhaps soon we'll only get deep fried squid or shrimp, animals that were once scorned from the dinner table for being 'bait' food.
Oh, wait, that's already happened.
The following is a blurb from Science magazine's writeup (subscribers only) about the new study (cite at the bottom).
"There is abundant evidence that fish stocks are being exploited at unsustainable rates in many sectors of the world's oceans. In order to gauge the extent of human impacts, it is necessary to assess where stocks stood in prefishery times; however, accurate analyses are hampered because records did not begin until many years, and often centuries, after initial exploitation.
"Jennings and Blanchard [the authors] have devised a method for estimating what fish abundances would be in the absence of fishing, using macroecology theory that relates abundance, biomass, predator-prey mass ratio, and efficiency of energy transfer between trophic levels in an ecosystem. Applying it to the North Sea fishery, they estimate that the current biomass of fishes larger than 4 kg is only about 2.5% of its pretrawling level, and the total biomass of all fishes is nearly 40% lower than it would have been. These effects are larger than those predicted from existing time-series data, and this approach may provide a useful basis for comparing the impacts of fishing across different ecosystems and different fish communities."
Fish abundance with no fishing: predictions based on macroecological theory, Journal of Animal Ecology, Volume 73 Issue 4 Page 632 - July 2004