I had heard this stuff about negative calorie foods before (supposedly celery), but had trouble believing stuff like tuna and shrimp would qualify. So I googled it, and at first it looked good: there are a lot of websites claiming lots of negative calorie foods. However, the wikipedia article on the subject seems to disagree:
While this concept is popular in dieting guides, there is no scientific evidence that any of the foods claimed as negative calorie foods are such. Foods that are claimed to be negative in calories are mostly low-calorie fruits and vegetables such as grapefruit, lemon, lime, apple, lettuce, celery, broccoli and cabbage.Celery, a commonly cited negative calorie food, actually requires only about 10% of its calorie content to be digested (due to the thermic effect).:88 Zero-calorie beverages, such as water, do take more than zero calories to process within the body, however they do not offer the dietary sustenance that other so-called negative calorie foods do in the form of fiber, carbohydrates, vitamins etc and as such, are not generally regarded as being negative calorie.
There is a issue that two feilds are using the same term for not the same thing.
For example, If you have two ponds, one is growing Carp, and the other is bass, the carp produce more calories then you will have to feed them, as they are low on the food chain, and thus are a very inexpensive source of food, while the bass require other fish to eat, and thus you will need to produce less calories per acre OR feed them additional foods so that you can have higher density. In Aquaculture, it is most often refered to shrimp farming, as the bussiness model is to take unwanted or low-value fish per pound and covert it to a higher dollar shrimp, even though it takes many pounds of fish to grow one pound of shrimp. Some greens think this is horrid as you can feed more people with the low-value fish then you can with the shrimp, even if market forces has shrimp being grown. however many times the fish being fed to the shrimp are low value since they are not worth taking to market as they are not what people want to eat, or happen to be what was caught when your where intending for another type of fish.
For example, it takes something like 13 pounds of Corn to produce 1 pound of beef.