How Do Fish Smell Underwater

For many years professional and avid sport fishermen have debated the use of scents and fish attractants for successful fishing with verified studies showing some incredible results on just how powerful a fish’s built-in senses used for survival are. Most species of fish develop a strong sense of sight and have lateral lines for picking up vibration and sound but, How do fish smell underwater?

A fish can detect odorous molecules in H2O. Like humans, their sense of smell is achieved by olfactory sensory neurons present in their nostrils. Biologists have discovered that fish have an extraordinary sense of smell about 400 x’s stronger than a bloodhound & up to 1000 x’s stronger than a human.

For many years professional sport fishermen have debated the use of scents for fish attractants when fishing. That still is the subject of debate but the fact that fish have the acute ability to smell is not. Through various studies on the subject, results show that most fish’s olfactory system allows them to detect very light odors, and for some species from very far away. For example, sharks can smell blood from several hundred meters away.

How Do Fish Smell

Fish have two openings (nostrils) on their head that contain an organ called an olfactory ro­sette that they use to smell. The larger this organ is, the more sensitive the fish is to the odors in the water.

In addition, fish have taste buds in their mouths, on their tongues, and in some cases outside their mouths. This combination of smell and taste organs allows fish to find food as well as avoid danger or repel certain scents that are unnatural to them.

Smells are transmitted to the fish by the water surrounding the fish.

Some fish (such as sharks, rays, eels, croaker, drums, and salmon) have developed an incredible sense of smell and can detect chemical levels as low as 1 part per billion. That means fish can detect 1/200th of a drop of a substance in 100 gallons of water. Fish use their sense of smell to find food, avoid predators, identify each other, spot safe habitats, and even locate spawning grounds. If the chemicals signal food, the fish will pursue the food. Or if the chemicals signal danger, it’ll flee. But fish use chemical cues in all sorts of ways.

A fish’s ability to detect the wrong or unnatural taste and smell can affect its ability to catch fish. If your bait has trac­es of human scent, gasoline, oil, sunblock, insect repel­lent, rust, mold, or even your aftershave and cigarettes on it, a fish might avoid it, or what is called Repel fish.

In the same way that you would not eat something that smelled or tasted wrong, a fish will not eat bait that has the wrong smell or taste. Other smells help attract fish that has created a market for fresh and saltwater fishing Attractants for game fish like Bass and Trout.

When fish are hungry and aggressive, they’ll hit the bait first and ask questions later. There you’re dealing with how long they’ll hang onto the bait. But when fish are negatively inclined to bite or picky that’s when you have to pay attention to details. That’s when you want to make sure you’re not presenting any negatives to the fish. Having a great sense of smell also helps fish find a mate, detect predators, and find fish they’re related to

Some fish have sharper senses than catfish. The catfish can smell a substance at a rate of one part per 100 million. American eel can detect substances at a rate of one per 10,000. Along with their keen sense of smell, catfish also have the ability to sense vibrations in the water.

This ability allows them to detect the presence of other prey in their immediate vicinity. They are also capable of detecting the vibrations of their prey, such as fish, crabs, and other crustaceans.

What kind of Smell Attract Fish Underwater

Scents that attract fish are also known as Positive Scents or Scent Tracks. They are a trail of odor molecules that fish give off whether they are swimming or hiding or freshly dead. These scent tracks let predators track down hidden or far-away prey items to eat.

• Fish can detect amino acids. Nature provides a library of 21 different amino acids, and particular fish are selectively responsive to specific amino acid cocktails.
• Fish can also detect bile acids in the water. These are compounds produced as a result of food digestion and are released from fish as part of the normal excretory process. Thus, bile acids serve as a cue that other fish are feeding, and that more food may be close at hand.

Salt, anise, and garlic are three positive smells. It is possible that garlic and anise are masking smells rather than attracting them. The smell or scent of the water surrounding the fish is transmitted to the fish. 

According to most anglers, they use scent on soft baits mainly Shad, Crawfish, and minnow Natural scents because of it being a favorite Largemouth food along with salt, anise, garlic, or for its uses in hiding human contact and chemical scents from manufacturing. Other fish like milk products like cheese.

If you decide to use Scents for fishing remember that the scents that utilize fish oil as a base stay on the bait quite well and disperse readily in the water leaving a “scent trail”. Baits with the scents “built-in” like Yum or Gulp baits work very well, and Scents you apply or spray on bait or lure like Smelly Jelly. When a fish detects amino acids, the message is, that food is nearby

• cheese
• fish slime
• fish guts
• fish extracts
• human saliva
  

Some fish can pick up chemical signals when immobile by pumping water through their olfactory system. This is a way for fish to sense certain smells. Some species of freshwater and ocean fish live where underwater visibility is very poor in many fisheries so they learn to use their underwater olfactory organs to smell bait.

A fish’s unique sense of smell and its ability to detect and respond to chemical “odorants” in the water can play an important role in how it interacts with its environment and the baits we present. That’s when you want to make sure you’re not presenting any negatives to the fish. Having a great sense of smell also helps fish find a mate, detect predators, and find fish they’re related to.

What Kind of Smell Underwater Repels Fish

Scents that repel fish are also known as Negative Scents. Any kind of chemical that would be unnatural to a fish-like, like gasoline, tobacco, or aftershave may end up on a lure or bait by making contact with the hook set. Others are:

• human skin oils
• nicotine
• bug sprays
• Sunscreens scented or not
• perfumed soaps-baby wipes
• any petroleum distillates like gasoline, marine grease, oil, or diesel fuel.

Can Fish Smell Human Scent

Since we established how sensitive a fish’s ability to smell is and the Negative and Positive scents that have a bearing on most fish reactions there is not much doubt that a fish can smell a human when fishing. This is a great video on how to take human scent when fishing out of the equation.

You can decrease your chances of of­fending a fish with Negative odors by simply washing your hands before handling your bait and lures. Avoid deodorant soaps since they have perfume in them. Ivory Soap is a common­ly recommended soap. Also, try natural ways of disguising your human odors. This is a great video on how to take human scent when fishing out of the equation.

Fish Smell Fishing Tips

A fish’s ability to detect the wrong or unnatural taste and smell can affect its ability to catch fish. If your bait has trac­es of human scent, gasoline, oil, sunblock, insect repel­lent, rust, mold, or even your aftershave and cigarettes on it, a fish might avoid it. In the same way that you would not eat something that smelled or tasted wrong, a fish will not eat bait that has the wrong smell or taste.

JimGalloway Author/Editor

Fishing Advisor-Can Fish Smell Odors?