1. Trimethylamine (TMA): TMA is a naturally occurring compound found in fish and other marine animals. When fish dies, bacteria start to break down the TMA, converting it into trimethylamine oxide (TMAO) and other compounds that produce a strong, fishy odor.
2. Enzymes and Bacteria: The digestive enzymes present in fish tissues continue to function even after the fish dies. These enzymes break down the fish's proteins and fats, releasing various compounds with unpleasant smells. Bacteria present in the environment also start to break down the fish material, contributing to the odor.
3. Spoilage Bacteria: Spoilage bacteria thrive in the warm and moist environment of a dead fish. These bacteria produce foul-smelling compounds as they feed on the fish's flesh and tissues, leading to an intense and unpleasant odor.
4. Protein Breakdown: As the fish decomposes, its proteins start to break down into various compounds, including peptides and amino acids. Some of these compounds have strong, unpleasant aromas, which contribute to the overall stink.
5. Release of Sulfur Compounds: During decomposition, the sulfur-containing compounds present in fish tissues, such as hydrogen sulfide, are released into the air. These compounds have a characteristic rotten-egg smell that adds to the unpleasant odor.
6. Environmental Conditions: Temperature and humidity play significant roles in the rate of fish decomposition and odor production. In warm and humid environments, bacterial growth and decomposition occur faster, leading to a more intense stench compared to cooler or drier conditions.
The combination of these factors makes dead fish smell so bad and contributes to the characteristic odor commonly associated with fish decomposition.