This is an excellent post from the Monterey Bay Aquarium. Have a look at the video as well:
I'm sure we all know what a magnificent animal the bluefin tuna is, however it isn't soft and cuddly like a giant panda and doesn't necessarily get the public attention it deserves, but that doesn't mean that they should not be preserved. From an ecological perspective they are an alpha predator and we don't fully understand what effect removing this animal has on the marine environment that we are dependent on.
We need to stop eating endangered species. The Monteray Bay aquarium does a great job of highlighting the seafood to eat and the seafood to avoid.
I have blogged previously about other regional seafood guides. Have a look.