Why did fresh haddock smell bad?

Fresh haddock can smell bad due to the presence of trimethylamine oxide (TMAO), which breaks down into trimethylamine (TMA) as the fish begins to spoil. Factors such as poor handling, improper storage temperatures, or being past its freshness can accelerate this breakdown, leading to a strong, unpleasant odor. Additionally, the natural enzymes and bacteria present in the fish can contribute to the off-putting smell if the fish is not fresh. Always check for a clean, briny scent when assessing the freshness of haddock.