How Well do Fish Smell?

 

A salmon can detect the smell of it's home stream five thousand miles at sea, and follow it home to spawn 2 to 5 years later.  This amazing ability allows the salmon to detect very small concentrations of some compounds in the water. 

The salmonid family can detect L-serine amino acid in quantities as little as 1 part per 8 billion.   This phenomena will work against fisherpersons as well as for them.   If you understand & take advantage of this information, you will put more fish in your fish-box.  There are many manufacturers of fishing scent that have dedicated clients with testimonials as to the effectiveness of their product.

SIGHT, SMELL & SOUND : In the sport fishing world there is documentation that this is mandatory if you plan on increasing your catch rate.  All of these working together will increase your catch percentages.  Any one alone can catch fish under the right conditions.  If the water is clear & shallow enough to allow light to penetrate, then SIGHT alone may be all that is needed.   However once you move to deeper, or murky water then things change dramatically.

How do you think deep sea fish find food?   It is dark down there below 100' so sight is probably out of the equation.  Sound made by the preys movement could very well be helpful.  But SMELL is also a very important item here. 

The photo below shows a Spiny Lathrope crab taken from the stomach of a 45# halibut pulled from 500' of water off Neah Bay Washington in the early summer of 2008 & is shown laying on the bottom side of the tail of the halibut that ate it. 

This crab was small, (about 2 1/2" across the body, not counting the legs) & was 100% intact, meaning it had just been picked out of the gravel on this bottom.  As you can see it is covered with a hairy type substance that would help camouflage & allow it to hide it in the gravel.  However the one thing that may have been a demise of this crab was that it was a female that was laden with eggs, a few of which can be seen as an orange mass on her under belly.  The mass of these eggs was 10 times the amount seen in the photo.  I am sure the eggs gave off a distinct smell separate from the crab itself leading to her demise.

SOUND would be from the vibrations of the lure in the water whereby the fish can zoom in as if it was radar.  How many times have you been in your yard & a younger person drives by with their sound system set so high using a BOOM BOX that you can feel them coming?

Again relationship to fishing for halibut in deep depths one common practice is when using a spreader bar ( a heavy wire in the shape of an Ell designed to separate the weight from the bait as it is descending to the bottom & to keep them from tangling) is to bounce it on the bottom occasionally.  It is known as "Ringing the Dinner Bell".  This creates noise of the up to 32ounze lead weight & the spreader bar when they hit the bottom inviting the fish to investigate.

Fish Attracted to Smells : For years the typical method of fishing for bullhead catfish was to set out a stink bait sack composed of chicken entrals, blood, and about anything that would decompose making a bait trail in the river or lake, then wait a few days before anchoring nearby to fish.

Sturgeon are another fish that uses it's nose to locate food on the bottom.  They eat clams, mussels, shrimp, dead smelt & about anything they can find on the bottom, many times in a murky situation so smell is a contributing factor here.

Good Smells :  This also means that a smell, or a scent can be used on a lure as an attractant to help you.  There are companies that make attractants for just this purpose.  These scents do two things; first they mask the L-serine that we all give off, but they can also contain amino acid profiles that appeal to fish to trigger feeding behavior.

Why Use a fish Attractant:   There are two widely published facts about Bass in relevance to an attractant:

1. These fish can detect 1/200th of a drop of substance in 100 gallons of water. 

2. A Bass or many other fish will spit out a bait within 2 to 3 seconds if it doesn't taste acceptable to the fish.   If the Bass like the taste it can hold onto it for as long as 30 seconds before spitting it out even though it may be an unnatural food to the fish.

The goal of all fisherpersons to hook more fish, and fish attractant manufacturers are competing for your business by producing attractors that will prolong the amount of time a fish will hold onto your lure, and ultimately increase your chances of setting the hook and landing the fish

One well known fisherman swears that coconut-scented Hawaiian Tropic sunscreen adds to his catch.   Another successful salmon fisherman who is a member of our fishing club, has found that Greatian Formula, "Just for Men" hair color has improved his catch on the days he darkened his gray hair with it.  This was not noticed happening over just a few days.  After he stumbled on this, he has been using it now for as good number of years & reluctantly passed it on at a club fishing seminar.

Do these scents work?   There has been many side by side tests done and unequivocally it has proven the effectiveness of the scents and attractants.   Ask about any tournament fisherperson, experienced anglers & guides if they use scent.   There are many ways to use these attractants.   Depending on the consistency, if it is a jelly, they you smear it on the lure or flasher that is being used as an attractor.  Some of these attractants are a liquid & designed to be soaked into a fly or yarn.  There are also capsules that attach to the line that have small holes to slowly dispense the scent.  There is one nylon bag sold by Silver Horde that has hatchery feed pellets inside that is attached to a downrigger ball to leave a scent trail in the lure's path.  This is specifically designed by Tom Nelson of Salmon University to attract returning hatchery Coho salmon.  

Smelly Jelly makes many scent attractants in different flavors if you will.   Berkley has their PowerBait attractants and jellies.  Other companies seem to pop up locally & are also effective.  These products come in liquid and gel forms, and can be spread on any lure to increase their fish catching potential.   Some lures incorporate scent directly into their softbaits like rubber worms or jig bodies.  The scent in these softbaits encourages fish to not drop the baits soon as they realize it may not be what they thought, giving you a better chance of a hookset.   Berkley has a huge selection of PowerBait for all species, including a new Inshore bait that has proved effective for halibut, and big lingcod.  At times it seems these bait companies are making a product to catch you & I more than the fish. 

Chinook salmon seem to prefer a mix of anchovy & garlic scent.  Bass & other warm-water fish seem to prefer crawfish & anis.

In the chart below taken from a well known fishing scent manufacturer in the Pacific NW, show what they have tested  & formulated for different species.

Do They Work? :  Well I can't twist your arm from here, but look at most of the successful fishing guides, some even have a special scent that they very carefully guard it's formula.   Using scent may allow you to catch more and possibly bigger fish.   Also keeping your hands clean, removing offensive odors off your tackle and adding fish attracting smells to your offering will up your odds for better days on the water.   Many fishermen will wear surgical gloves when baiting up & if you seem to not be catching the fish you think you should, then this would be a very simple & possibly rewarding experiment.

Clean Your Lures After Use :  One related thing here is that IF you do use scent on your lures, that it can get rancid & collect debris in your tackle box over time when not cleaned off after usage.  Many dedicated fishermen make a point of carefully cleaning it off the lure at the end of the day.  Therefore it will behoove you to make a practice to use Lemon Joy & wash off the scent before you put the lure away.     Others discard their bottled scent each year & buy a new supply, thinking that it deteriorates.

Detrimental Smells : Mammals, humans included, give off a chemical called L-serine where studies have shown do repel fish.  Also this is why some people just can not seem to catch fish as they give off more L-serine than others do.   I knew twin brothers, one of which could catch fish blindfolded & one arm behind his back, while the other had to really try even to get a bite, this possibly was the situation with them.    So what does that mean to you & I as a fisherperson?  It means that salmon, as well as trout and other game fish, can smell you or any contaminating scent if you may have handled even the lure without gloves. 

Studies have been conducted in fish ladders of dams & have shown that people who give off very little L-serine can stand in the passageway with their shoes off and fish will continue to move through, whereas people who give off lots of the chemical will stop all upstream movement through these passageways.

There are other chemicals that the fish do not particularly like.  Gasoline is one high on this list.  So if you are refueling your gas tank or are connecting your fuel line to your motor and it leaks a bit,  or you check the oil level in your engine, you may need to wash your hands if you want to catch any fish the rest of the day.   Years ago, I knew a commercial fisherman who before he started his inboard engine each morning would pull the dipstick to check his oil.  When he was finished, & before he touched any of his gear, he would wash his hands.  One soap that has been used by many guides for years is the liquid dishwashing soap, Lemon Joy.

Charter boat captains have said that the smell of onions, potato chips & fried chicken if you get it on your hands when you ate your lunch & then got it on the line, lures etc. will kill a bite also.  If this type of food is in your lunchbox, it might well be best to use latex gloves to eat with so the bad scent does not contaminate your lure, line sinkers etc.  Other smells that may cut down your angling success include foods like peppers, some hand lotions, liquids etc. even cigarettes,

Insect repellent is another bad smell, the various insect lotions and sprays are not an attractant, but do act as a repellant to fish.    They can also have a detrimental effect to the finishes some of your gear or lures.   Fisherpersons may find it advisable to carry one of the biodegradable soaps with them and wash their hands often to remove all odors possibly offensive to the fish.

This is my shortest fishing article, but probably one of the most important to fisherpersons.

 

Copyright © 2005  LeeRoy Wisner  All Rights Reserved 

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