A number of animal species have been covered here as a food during a survival situation, but ALL pale in comparison to fish! Fish are abundant and difficult to exterminate and supremely nutritious. These characteristics lead me to believe that fish could very well be my number one food of choice during a SHTF scenario.
Local availability is obviously a concern. If you are living in a desert fish may not be anywhere on your food list.
Availability of fish is of prime importance to me and to past civilizations as well. Human civilization developed along rivers and it wasn't just for trade either. Rivers are lush rich productive environments for food and building resources as well. Fish can provide quick meals if you go fishing for them but also provide food the lazy, efficient way, trapping and also can be raised for food in small holding ponds where they can be plucked at will. So yeah, don't forget aquaculture. Raising your own fish for food could be a literal life changer in a SHTF scenario.
Here is information on how fish can provide food for you.