Not everything we should do to be greener needs to be government mandated.
Eating fish and seafood that is good for our health without depleting the stock or damaging their eco- system is an individual choice.
A simple way to give thanks for Thanksgiving is by visiting sites such as Oceans Alive, check their Best and Worst List and jot down notes as to what we should (or not) purchase in a store or order in a restaurant.
Some such as Halibut can be Worst if from the Atlantic and Best if caught in the Pacific (Alaska to be specific).
In need of recipes for the holidays, check these Sustainable Seafood Recipes from the 2004 book of the same name, includes Mussels with Lime and Basil by Chef David Waltuck of Chanterelle fame. 
For meat eaters with a conscience, read what Tree Hugger had to say about The River Cottage Meat Book.
I hope this helps you have a guilt free meal for Thanksgiving.
La queue du poisson for Green Day #6
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