Few of us get the chance to enjoy the experience, but very fresh fish smell surprisingly like crushed plant leaves! The fatty materials of both plants and fish are highly unsaturated, and both leaves and fish skin have enzymes (lipoxygenases) that break these large smellless molecules down into the same small, aromatic fragments. Nearly all fish emit fragments (8 carbon atoms long) that have a heavy green, geranium-leaf, slightly metallic smell. Freshwater fish also produce fragments that are typical of freshly cut grass (6 carbons), and earthy fragments also found in mushrooms (8 carbons). Some freshwater and migratory species, especially the smelts, produce fragments characteristic of melons and cucumbers (9 carbons).