Think globally. Act locally.

I came across this link from the Audubon Society. It is a wallet card that ranks seafood from species that are not in danger, to species that are overfished and in danger. I was surprised to see where canned tuna, Atalantic cod, grouper, shrimp, farmed salmon, orange roughy, and snapper were on the list.

The Audubon Seafood Wallet Card

Abundant and well managed species.
Farmed mussels and clams
Alaska salmon
Mahimahi, troll caught
Crawfish
Alaska halibut
Dungeness crab
Tilapia, U.S. farmed

Significant concerns about species' status, fishing methods, and management.
Yellowfin, bigeye, albacore tuna pole/troll caught
Catfish
Striped bass
Mahimahi, longline caught
Pacific cod
Pacific flounders and soles
Rainbow trout
American (Maine*) lobster
Squid (calamari)
Ahi Tuna (yellowfin and bigeye tuna steak)
Canned tuna

Many problems with species. Severe depletion, overfishing, and poor managment.
Swordfish
Atlantic cod
Groupers
Shrimp
Atlantic flounders and soles
Monkfish
Sharks
Farmed salmon (including Atlantic)
Orange roughy
Snappers
Chilean seabass (toothfish)
Atlantic halibut