Ontario Fishing Network
E-Magazine
www.ontariofishing.net
Volume 8,  Issue 4 - Apr. 2008  #88

Got Scent?
By Justin Hoffman

There are many different commercial fish attractants. From aerosol cans to squeeze tubes and jars to jellies, tackle store shelves are literally soaked with a wide range of these products.

For the most part, motion, shape, noise and water displacement are the primary stimuli that cause fish to strike a lure. Most game fish sense and are attracted to your lure long before smell or taste figure in the picture. Once fish get close enough to your bait and commit to striking, taste and smell certainly have an important impact on their final decision. This is best illustrated by a bass spitting out your lure in the blink of an eye. Although the fish was initially interested in your presentation, it had a negative reaction upon mouthing the bait, causing it to turn its nose up at a "prey" it deemed inedible.

Catfish lead the way with the most sensitive smell of all freshwater fish. Carp follow closely, while bass and walleye are in the middle of the pack. Pike and muskie are at the tail end. For those who chase catfish or carp, then, scent is an important key to success, as these fish will most likely smell your bait long before they see or hear it. And although bass are neither at the top nor bottom of the list, tests by renowned bass researcher Dr. Loren Hill show that they can detect a preyfish odour source at a distance of 25 feet. Furthermore, studies conducted by Dr. John Caprio and his Louisiana State University group have found that bass can taste a dilution of four ounces of the amino acid L-arginine mixed into 6,000 gallons of water.

What's In The Bottle?
Fish attractants comes in myriad scents and tastes, ranging from the natural to the slightly weird. Oils extracted from such natural prey as crayfish, shad or other baitfish, nightcrawlers, or shrimp are the active ingredients in most scents. Other ingredients can be garlic or anise extract or other non-animal materials.

Specific ingredients or concoctions used to manufacture fish attractants mostly remain a secret.

Masking Those Negative Smells
"Bug spray (DEET), sunscreen (PABA), fragrances, and nicotine are substances that are repulsive to fish," stated Pure Fishing Research Director Dr. Keith Jones. "Some substances, like DEET, are highly repulsive. Studies done in our labs demonstrate that largemouth bass, and probably many other species, can detect, and are repelled by DEET concentrations as low as 1 part per billion. Other substances, detergents for example, are also extremely repulsive, as well as quite lethal. Nicotine would be only mildly repulsive."

One trait most fish attractants have is the ability to mask or neutralize scents deemed negative. The favourable molecules in your fish scent will adhere to the unwanted molecules that have been placed on your lures, equating to a positive smell, if the molecules are of the right size, or no smell, if they're the wrong fit.

"Masking agents work in two ways. One way is to dampen offensive odours and tastes by mixing in positive substances. The positive agent confounds the chemosensory system, diluting the offensive nature of the repellent. In the other strategy, the masking agent actually limits physical contact with the offensive agent. Oil-based scents operate in this way. They overlay the molecules of a fish repellent with an impermeable barrier, thus preventing the repellent from dissolving into the water and reaching a bass's chemoreceptors," wrote Dr. Jones in his book, Knowing Bass - The Scientific Approach to Catching More Fish.

Bass, like humans for example, have two nostrils slightly above their mouth. Each nostril has a separate hole that water-borne scent travels into and out of. Also believed is that taste and scent receptors can be found within and on the outside of their yap.

A receptor cell is necessary to distinguish certain tastes or smells, thus sending a positive or negative message to the brain. Water-borne molecules come in all shapes and sizes. A receptor cell will only allow the correct size and type of scent molecule to make it into the cavity, thus sending a signal to the brain. If the wrong size or type of molecule is offered, then no signal will be sent.

"Fish chemoreceptors (essentially small pockets into which the stimulant molecules fit) can accommodate only small, water-soluble molecules in the size range of about 50 to 500 Daltons (a measure of molecular weight). Those molecules that are too large to fit into the chemoreceptive pockets are not able to stimulate either the fish's olfactory (smell) or gustatory (taste) system," said Dr. Jones. A good molecule will elicit a positive response, while a bad one will be deemed negative.

So, by covering unwanted and negative smells we leave on baits, fish scent can play a large part in getting fish to strike that may not otherwise do so. This is by far the greatest benefit that fish attractant have for an angler.

Longer Hang-Time
Have you ever wondered how many times your jig and grub is spit out by a wary walleye, or your tube bait is mouthed and expelled by a smallmouth bass? It happens more than we think, and many times it goes unnoticed.

Fish scent, whether through taste, smell, or masking properties, will often entice a fish to hold on to your bait longer, allowing extra crucial seconds for you to set the hook. I've had some fish chomp down on a lure for upwards of twenty seconds, leaving me to conclude scent definitely does make a difference.

Dr. Jones' research had similar findings, albeit of the scientific kind. "In the lab we frequently run bait 'taste tests' wherein a fish is offered a small piece of softbait. Accurate counts are made of the number of times the fish rejects the bait (i.e. spits it out) versus the number of times the bait is consumed. Fish like bass and bluegills typically reject pieces of plain (non-flavoured) softbait within one to two seconds, and virtually never eat one. In contrast, pieces of Power Bait are consumed about 95% of the time, and Gulp! Is consumed at a rate of 99.9%."

Which Scent Works Best?
Knowing what species you're targeting helps in narrowing down a scent. Crayfish are high on the diet of small- and largemouth bass, for example, so generally choose a scent in this flavour when gunning for these guys. When chasing walleye, a nightcrawler or baitfish flavour often gets the nod.

Oddball scents like garlic are also worth looking into. As time goes by, you will begin to build confidence with a certain brand or specific scent.

When To Use It
You can employ scents in all conditions and time periods, but certain situations definitely dictate their use. When fish are in a negative or neutral mood, such as during cold-front conditions or in heavily pressured waters, scent can up your odds.

Cold-water conditions, such as those from fall through spring, also call for the use of scent. Fish can be finicky then, due to lowered metabolism rates, so taste and smell are often triggering factors. Although commercial scents are less widely used during winter, likely because many anglers turn to live bait then for the real deal in taste, scent, and action, I've been experimenting with them during the ice-fishing season. The results have been promising.

Any vertical presentation, especially when working a bait slowly and methodically, deserves an extra helping or two of scent. Fish have a longer time to inspect baits, so giving them something that smells positive is always a good bet. The same goes when working heavy cover.

Commercial fish scents are not magical elixirs, but they can be used to your advantage. The attractants of yesteryear, although pleasing to the nose for humans, didn't contain the specific attributes or chemical makeup necessary to arouse fish. Simply put, manufacturers were under the misconception that fish could smell and taste the same as us. Scientists, through exhaustive testing, have a better understanding of what substances trigger a feeding response in fish today. And by narrowing down what water-soluble chemical substances stimulate fish to feed, the fish attractants they now produce provide positive stimuli that elicit equally positive results.

In the angling world, however, you still need skill, knowledge, and determination to catch fish. Using scents, no matter how good, can never take the place of experience on the water. Take a look at fish attractants the next time you troll the tackle aisle, though. You will be glad you did.

Side Bar : Oil or Water-Based?
Water-soluble scents can work to attract fish to a lure, however, oil-based products cannot. Due to their insolubility in water, oil-based scents make excellent masking agents, but provide little else in the way of actual attraction.
Fast-dissolving water-based scents provide the best attraction properties, whereas slow-dispersing scents will increase the retention time of a lure.

Side Bar : Amino Acids Rule the Roost
According to Dr. Jones, amino acids play an important role in what fish choose to eat : "Fish feeding is stimulated by small, water-soluble molecules typically associated with aquatic prey. Depending on the species, these would include various amino acids, sugars, amines, and nucleotides. Individual amino acids - the building blocks of all proteins - are the right size and shape to fit the chemoreceptive pockets, and generally, are highly stimulatory to both fish taste and smell. Amino acids are, by far, the most common feeding stimulant in fish."