Well, you certainly have been giving your taste buds some stimulating adventures! :-)
Perhaps some questions are in order:
1. Do you know the source of the fish? Could it have contained toxic metals? (Quite common when fished from waters where there is commercial activity.) Acute poisoning from various sources can leave a bitter taste in the mouth (acute mercury poisoning, cadmium, etc.),
2. Could something non-food related be creating this bitter-taste sensation, such as new chemicals in your environment (from, for example, new furniture, carpeting, paint, etc.)? This might cause post-nasal drip or direct irritation from inhaling, etc.
3. Could this be bitter-taste be acid-reflux?
There are dozens of possible explanations for this symptom. Perhaps eating plenty of fresh vegetables and fruits as well as drinking plenty of plain water for the next few days will eliminate the source. Otherwise, you can further research causes for bitter taste in the mouth at wrongdiagnosis.com
http://www.wrongdiagnosis.com/symptom/bitter-taste-in-mouth.htm
Good luck and careful with the fish. Some fish is better for you than others.