I'm going to try to explain this ammonia thing a bit, just so everyone knows what's happening.
First, all living things, particulary animals with their muscle tissues and such, are made up of proteins.
Proteins in tissues that are old or no longer needed are broken down into urea by the body and transported by the blood and excreted in renal glands, such as, or similar to our kidneys.
Bleeding a fish eliminates the urea in it's blood.
Putting the fish on ice cools down the muscle and other tissue to stop any further protein/urea conversion.
All animals have organisms living within them, including fish and other creatures. This includes some bacteria capable of converting urea to ammonia.
If you don't cool your fish quickly enough or fully, the bacteria in the muscles and elsewhere change urea to ammonia and ruin the taste and smell.
Some types of fish, shellfish, and crustaceans (crabs, shrimp, lobsters, etc.) have higher concentrations of bacteria in them because they are scavengers and eat other dead animals. These guys therefore spoil more quickly than the rest, but all fish, shellfish, and crustaceans will spoil sooner or later, unless frozen, or cooked and canned (sterilized).
Hope this is useful in understanding what's going on with your catch!
Now for some crab cocktail!
Joe. :smilep