Professional fishermen know that certain species of fish have an incredible sense of smell and use that sense of smell when attracting fish with lures and baits catching trophy-size fish just like they would using colored lures or crankbaits that use sounds like rattles to attract largemouth or other desirable fish. Can fish smell underwater?
Yes, most fish can smell underwater & it’s estimated that a fish’s sense of smell known as olfaction is around 1,000 x’s better than a human’s, a highly developed sense of smell, in which smells or odors are perceived, detecting desirable foods, hazards, and pheromones, and plays a role in taste.
A Human nose has the dual purpose and the ability to smell and breathe, but these two functions are completely separated in fish where nostrils are for smelling, and gills are for breathing.
Can Fish Smell Underwater
Yes, most fish can smell underwater and are pretty good at it. It is estimated that a fish’s sense of smell is around 1,000 times better than a human’s sense of smell. A fish’s sense of smell is known as olfaction or chemoreception, and it is part of a fish’s chemosensory system that allows them to detect chemical stimuli.
Fish seem to have a highly developed sense of smell, which has many functions in their life underwater, from finding mates to locating food in the water. The sense of Smell, or olfaction, as scientists call it, is an important sense for many fish. Fish have holes on their snout that look like nostrils are called nares.
Not all fish move water in and out through these nares in quite the same ways, but the key to a strong sense of smell for fish is the ability to move water rapidly over these sensory pads. Some fish can pick up chemical signals when immobile by pumping water through their olfactory system via tiny hairs called cilia.
Other fish can pump water through muscular movement. Some fish, have an olfactory system that requires them to swim in order to get water moving through their nares. When the sensory pads pick up chemical signals, they transmit them to the fish’s forebrain, which interprets the signal and incites the fish to respond appropriately.
How Do Fish Smell
Fish can’t use their gills to smell, so they rely on their olfactory system to detect odor molecules in the water. A fish’s gills have filaments that take oxygen dissolved in the water to be absorbed into their bloodstream, so they have no real use for breathing out of their nares.
A fish’s respiratory system that they use for breathing is not linked to a fish’s nares, since it is linked to their olfactory system.
Each nostril in a bony fish actually consists of two openings. Water passes into the forward opening, flows past the fish’s sensory cells, and exits through the rear opening.
Fish that live in darker, murkier water environments have to rely more on smell to sense the environment they live in, compared to fish that live in clearer, brighter water, which rely more on their eyes instead.
Fish sniff the water coming through their nostrils also called nares to detect chemicals in the water, which can help them avoid predators, locate mates, and also direct their migration. Some of these scents are pheromones, that are chemicals released by other aquatic creatures that can trigger some kind of response in the receiver.
Say an injured fish that has been bitten by a predator may give off a scent that triggers an alarm-type response in other fish of that species, warning them all to flee and escape from the threat.
Salmon species use their keen ability for smelling their way back to the streams where they were born based only on the chemical composition of the water in that stream that they used.
Science Direct: Olfaction