Far too many fisheries are overfished, it's true. But managed right, fisheries can supply the world with a lot of food that it sorely needs. If you eat fish products that are certified with the Marine Stewardship Council mark, you know that the fishery is sustainably managed, with a good security margin and issues such as by-catch and seafloor damage adressed.
MSC is awesome. It's the reason I joined WWF - they had a big hand in creating it, and it's an example of the great work they do.
But even if you can't get MSC-certified fish, there are fisheries which are close to getting the certification, or are managed sufficiently well that they are in no danger of collapse. Your local WWF organisation will probably have more info. Eating fish from these is far preferable to chicken, turkey and pork, because farmed animals eat food that could have gone to humans (and lots of it! most of the calories are "wasted" by the animal for such things as moving about and maintaining body temperature). Caught fish do not.
For the record, yellow fin tuna is on WWF's "yellow" list - don't eat much, and only if you know it's from a good source. Bluefin is on the red list. I order veggie sandwiches instead, and eat MSC pollock and green-listed haddock for my protein :-)
in July 2008