Fish have a sense of smell about a million times better than humans. This is scientific fact. In their water world, they are continually sensing both good and bad odors as molecules of scent, taste, and odor diffuse their way from both live and dead food sources. Sharks can follow just a few molecules of scent to it's source from miles away. Other fish aren't far behind.
Fish depend on their sense of smell to find food.
You can help them. Once they get interested, they might strike because of sight, vibration, lure action, or because they see or smell food. People have caught all kinds of fish without scent. They've used rusty hooks and rotten bait and caught fish. They rigged wrong and used cheap line and caught fish.