A little note on fish...
Rather than go into specific environmental or health concerns for every single species of fish and shellfish we eat, I just want to say that it is important to put a little more effort into researching the seafood you eat. Our oceans, rivers and streams are sensitive and damaged, our sea life threatened by many factors. Much of this harm is caused directly by the fishing industry, and we support them every single time we buy or eat much of the fish widely available. Because each individual species is under different and ever-evolving pressures, it would be pointless for me to try to list what is OK and what is not in this forum. This list changes from season to season and every region has its issues.
Instead, I am including a few links that will help inform your decisions at the restaurant and the grocery store. Its no longer excusable to turn a blind eye, fish is not as safe of an alternative as some think. It is crucial that we are aware of the impact that the fish industry has on the planet and take responsibility for our role.
Here are some really great, comprehensive guides to ocean-friendly seafood.
The Blue Ocean Institute - They offer a service where you can text the name of a fish and get up-to-date sustainability info instantly! Beats those wallet cards that never seem to stay in your wallet anyway.
Environmental Defense Fund -The Seafood Selector is great.
The Monterey Bay Aquarium's Seafood Watch Program
The Seafood Choices Alliance - This one is geared toward those in the field, but is very helpful and informative for everyone. There just may be a few unfamiliar fishing terms.
And especially, look for fisheries using the seal of the Marine Stewardship Council.