1. Trimethylamine Oxide (TMAO):
This is a compound that fish produce to help them survive in the ocean. It acts as a protectant against changes in pressure and temperature, which are common in the deep sea. However, when fish die, bacteria break down TMAO into trimethylamine, which has a strong, fishy odor.
2. Other Volatile Compounds:
Fish also contain other volatile compounds that contribute to their smell, including ammonia, dimethylamine, and various fatty acids. These compounds are produced as byproducts of their metabolism and decay after death.
3. Skin Mucus:
Fish have a layer of mucus on their skin that protects them from parasites and infections. This mucus can also contribute to the smell of fish, especially when it starts to decompose.
4. Diet:
The diet of a fish can also affect its smell. For example, fish that eat a lot of algae or plankton may have a more earthy or grassy smell.
5. Handling and Storage:
The way fish are handled and stored can also impact their smell. If fish are not properly cleaned and stored, they can develop a strong, unpleasant odor.
It's important to remember that:
* Fresh fish have a mild, pleasant smell. The stronger, fishy smell is more associated with fish that have started to spoil.
* The smell of fish is a natural part of their biology. It's not necessarily an indicator of bad quality, especially when it's mild.
If you're unsure about the freshness of fish, it's always best to err on the side of caution and avoid buying it.