It happens to all of us. There are days when everything seems right, yet we simply can’t connect with the fish. If no one else is catching, it’s likely the fish are simply not feeding. But what if you are fishing the same water, with the same gear as everyone else, yet you are the only one skunking? That scenario happened to me (again) last year.
David and I were standing in one of his many boats, watching a pod of Almanor’s chunky trout feeding on a Blood Midge hatch. Unlike the dainty midges that often frequent rivers, these ruby-red critters are half an inch long and as thick as an eight-penny nail. Looking into the Tanqueray-clear water, we could see the fish feeding just a couple of feet down. Occasionally, a fish would snatch a fly from the surface, leaving a big swirl and causing one of us to say something inappropriate. Having fished this hatch numerous times, we knew exactly what to do. Success was inevitable. . . .
I dug two size-10 pupa patterns from the (surprisingly) well-organized fly box and handed one to David. Neither of us had much luck at first. A couple of fish came to our flies, only to shear off when they got close. I thought about changing to a different pattern, but this one had done well in the past, so I figured it was worth sticking with it a little longer. About ten minutes later, a modest-size brown trout got very close to my fly before swimming off. I watched the same thing happen to David, though to be honest, the rainbow that spurned his fly looked to be well over twenty inches, one of the bruiser trout that make Almanor such a thrilling fishery. About minutes later, David finally hooked up. A large rainbow hit the fly quite hard and was on in an instant. Seconds later, a fish boiled behind me, and I made a sloppy back cast in an attempt to cover it. As the line headed out, there was an unmistakable “tink” announcing that my fly had just bounced off something hard. Sure enough, the hook point was shot. I hastily tied on an identical fly and got back to fishing. In the next fifteen minutes, David landed one more fish and lost a big rainbow that rocketed out of the water and performed an athletic, hook-shedding cartwheel. Meanwhile, two fish came to my fly, only to turn away when they got close, just as the fish had done at the start of the session. Then, wouldn’t you know it, the bite stopped. David had enjoyed some stellar action, while I had the stench of skunk.
We buy or tie flies that look like something natural, or at least something edible. If a fly doesn’t work, we assume it looks or moves wrong, or we aren’t using the right tippet, leader, or line. I am pretty sure most of the time this assumption is correct. However, anyone who has fished long enough has experienced days like the one I just described. Everything appears to be right, but for some reason, you can’t get bit. I don’t fish in ultraclear waters too often, which makes me wonder how frequently this scenario occurs without me even knowing it. I found myself wondering, “Do flies sometimes smell bad?”
A Confession
It’s time for me to fess up to intellectual laziness. Despite having known that some species of fish have an extraordinary sense of smell, I largely ignored this when I went fishing. Like many fly fishers, I was primarily concerned with how my flies looked and moved. My horizons started to get a bit wider in 2006, when I decided to investigate how top-water patterns sound underwater. A collaboration with fly designer and longtime friend Lee Haskin led to some fascinating discoveries about the sonic signatures of poppers, sliders, and divers, discoveries that still influence my time at the vise and on the water. But for some inexplicable reason, the issue of smell didn’t enter my thoughts until after the Almanor session. That’s when I started to read the scientific journals and discovered that I may have been unwittingly skunking myself and my friends, too.
Smelly Flies?
We assume our flies don’t smell, because even when we put them right under our nose, there’s nary a hint of any odor. Unfortunately, this sniff test isn’t telling us the whole smelly story. In fact, it isn’t telling us much at all. Just because something doesn’t smell in the air, doesn’t mean it doesn’t smell underwater, and vice versa.
Drop your fly into water and a number of substances will dissolve out, creating an odor cloud (more like a comet tail in flowing waters) that surrounds the fly. You see this effect every time you put a tea bag into hot water. When a fish moves into this cloud, it will inevitably detect a suite of odors. Some will increase the chance your fly will get bit. Others will have no effect. And, as you might suspect, some odors pretty much guarantee you won’t get bit.
Fish detect odors by moving water through structures called nares — they resemble nostrils. Look closely at the head of a trout, and you’ll see them just in front of the eyes. The nares connect to an organ called an olfactory rosette, which is covered with receptor cells, each of which responds to specific odors. When the cell detects an odor, it sends a signal to the brain. This alerts the fish to the presence of things like food, mates, or predators.
These odor-receptor cells can be incredibly sensitive. For instance, tests on rainbow trout have shown that they can detect some odors in the parts per billion (ppb) range. For most of us, this kind of number can be hard to visualize. The typical description of one ppb is a drop of water in an Olympic-size swimming pool. However, after countless times trying to explain such incomprehensible numbers in public meetings, I find folks relate to things more quickly when they are scaled to the situation at hand. A fish might be able to smell our fly from the other end of a swimming pool, but no one I know actually fishes in a swimming pool. We need something more intuitive.
My experiences in clear-water venues such as the Fall River, the Kennet (a chalk stream in England), and recently at Lake Almanor have been that fish seem to refuse my flies when they get within six inches. So the question becomes, how small is the odor source that produces one ppb just six inches from your fly? Clearly, it’s going to be smaller than a drop, but by how much? I’ll spare you the math. You need to reduce the volume of the drop 168,000 times. This tiny droplet is not much bigger than a skin cell — you’ll need a microscope to see it. An incredibly small amount of the wrong stuff on your fly could potentially set off alarm bells in a fish’s head. Imagine how nightmarish tying flies would be if fish had this level of sensitivity with sight.
Research on fish olfaction is still relatively limited when compared with other scientific fields, covering only a small number of fish species and odors. In all likelihood, there are hundreds, if not thousands, of odors that fish can detect at very low levels. The $64,000 question is, which odors will make fish snub our fly, and what can we do about it?
Sunscreen, DEET and Gasoline
It is common knowledge that fish do not like sunscreen, insect repellents, nicotine, and gasoline. I say “common knowledge,” because I can’t find any scientifically validated data to back this up. Some of these products have purportedly been scientifically tested, but I haven’t been able to find this work published in any of the regular journals. This may be because the tests were conducted by businesses, not research institutions. Given the lack of scientifically validated data, I think it is best to assume these products might be repulsive to fish.
The Smell of Bear
It appears that most fish have a combination of innate (evolutionarily derived) and learned (experientially derived) reactions to a wide range of odors. A great example of an innate odor response is how salmon react to the smell of bears. In a beautifully simple, yet effective test, researchers lowered a piece of bear skin into the water upstream of a school of salmon. The whole school quickly moved across the river.
“So what?” you might be thinking; “I don’t wear bearskins and rarely fish in the company of bears.” The point is that bears are mammals, and so are humans. This means we share similar skin chemistry. Indeed, a paper in the Journal of General Physiology showed quite conclusively that all Pacific salmon species react to rinses of human skin in the same way they do to bear skin.
The tester, wearing rubber hip boots, stationed himself just upstream from a sandbar which formed an obstruction making it necessary for the salmon to pass through a narrow opening about 2 feet deep. Two observers were stationed several yards downstream. When the fish (usually about 20) reached the constriction the material to be tested was introduced upstream. A hand rinse immediately scattered the salmon back downstream and they returned in ca. 5 to 10 minutes.
Modern olfactory research uses cool stuff such as functional magnetic resonance imaging and extremely fine-tipped microelectrodes inserted into individual receptor cells. This research has identified some of the substances to which fish’s brains react. As the earlier researchers had suspected, fish react very negatively when they detect extremely dilute solutions of L-serine, an amino acid found in and on the skin of all mammals.
The picture likely gets more complicated when we fish waters where catch and release is practiced. In these waters, fish may get caught and released multiple times. With each encounter, they have the opportunity to learn to associate an odor (or suite of odors) with danger. This may include amino acids and many other substances present on our flies. The older (and probably bigger) the fish, the more likely it is to be conditioned to respond negatively to such odors. Any number of chemicals that humans apply to their skin or secrete through their pores or that are part of the mix of materials used to make a fly could induce this learned response.
Schreckstoff
Another odor-related factor that may influence your fishing success involves a substance called Schreckstoff (aka alarm substance). This chemical is released by trout and many other species of fish when injured. When fish of the same or related species detect Schreckstoff, they exhibit antipredator responses, such as fleeing. Not surprisingly, this dampens their enthusiasm for your fly.
Now I don’t know if the injury of hooking is enough to produce a significant amount of Schreckstoff, but it bears thinking about. Caution would seem to suggest that if you know the location of a large fish and are hoping to get it to take your fly, you should probably avoid fishing directly upstream from it. Researchers have recently identified the types of chemical that cause this response — oligosaccharides of chondroitin sulfate. Chondroitin may sound familiar to some of you. It happens to be the main ingredient in joint supplements that many folks take for arthritis.
Masking Odors
So it seems that many species of fish can detect numerous odors at incredibly low levels. Is there anything we can do about this? Steelheaders have long advocated rubbing your hands with anise or vanilla. The idea is that these fragrant food additives overpower or mask any fish-scaring odors. Given how strongly these food additives smell to humans, the idea sounds quite plausible. However, I have my doubts.
First of all, even humans can detect underlying odors that supposedly have been masked. You don’t need a research lab to prove this. Anyone who has used a can of air freshener to “detox” a restroom is aware that it never truly masks unpleasant smells. To quote the hilarious PooPourri ad, “all you get is a blend of chem-lab carnations with just a touch of feces.”
The CIA looked into the subject of odor masking, and their findings were declassified in the early nineties. Their research showed dogs could readily identify a wood block that had been touched by only one finger for a couple of seconds (far less time than it takes to tie on a fly), even when it was “masked” with strongly odorous substances such as bergamot, oil of cloves, or wild marjoram oil. If dogs, with their superior sense of smell, can readily detect human odor under such conditions, it is likely fish can, too.
Finally, the biochemistry of olfaction would seem to cast further doubt on odor masking. Odor receptor cells work a bit like a lock and key. If the key (odor molecule) fits into the lock (a specific molecular site on the receptor cell), the cell responds by sending a signal to the brain. Therefore, in order to mask a fish-deterring odor, the masking agent has to block the active site on the receptor cell. To do that, the agent’s molecular shape, charge, and size have to closely match those of the fish-deterring odor. The molecule responsible for the smell of vanilla (vanillin) is not shaped like many of the natural (or applied) chemicals associated with human skin, saliva, or sweat. This means that even if the fish smells vanillin, it’s unlikely to suppress its ability to smell other odors, including those associated with danger.
It seems to me the most likely reason why vanilla or anise may have a positive effect has nothing to do with masking. If these scents are effective, it’s probably because they are mildly attractive.
Eliminating Odors
Since it seems unlikely we can truly mask the odors on our flies, all we can really do is try to eliminate or at least reduce them. Given that the
amino acid L-serine is known to scare the bejesus out of trout, salmon, and numerous other species of fish, removing that would seem to be the highest priority. Thankfully, you don’t need to use sophisticated lab decontamination protocols. The best way to get rid of amino acids is to simply wash them off with soap and hot water. You can also use dishwashing detergent, though bar soap (according to some researchers) is a bit better at removing amino acids. Since the idea is to eliminate smells, don’t use scented soaps or detergents.
A full surgical scrub is obviously the best way to make your hands clean, but this seems like overkill. Just wet your hands, lather thoroughly with soap, and rub them together. Pay attention to the fingertips, since this is where you are most likely to transfer odors to your fly. Follow this up with a thorough rinse, and dry your hands on a clean paper towel. You might want to consider lubricating your knots with water from the river or lake instead of saliva. There’s not much point washing your hands if you subsequently slobber L-serine (which is present in human saliva) all over the knot.
For folks who tie their own flies, the decontamination process should start before you even sit down at the vise. Wash your hands before you touch any hooks, bobbins, or tying materials. Once you have clean hands, keep them that way until you have finished tying the last fly. That means no snacks, smokes, or scratching. Some fly-tying materials can be odorous. Since there’s no way of knowing for sure if fish can detect the odor, it’s probably best to assume they can. If something stinks, try to find an alternative. You can wash stuff like capes and bucktails, but this can be risky. You really don’t want to have an expensive cape become home to bacteria and fungi. It’s probably best to leave these materials as-is and deal with the completed fly instead.
Deodorizing Flies
Since we can’t tell whether our flies smell underwater, a simple precaution is to assume they do and wash them. This makes sense whether you tie your own or buy them. Simply drop them into a clean bowl filled with unscented soap and hot water. Stir well with a clean spoon and let them soak for about half an hour. This will ensure the soap solution works deep into the materials. After the soak, dump the flies into a clean kitchen sieve and rinse thoroughly under hot tap water. Dry the flies on a clean paper towel before carefully putting them into your fly box (with clean hands).
Last, but clearly not least, make sure you have clean hands before you tie on a fly. Applying stuff like sunscreen or DEET should be done before you get on the water. If this isn’t practicable, you’ll need to decontaminate your hands before resuming fishing. I’d suggest you stay away from hand sanitizers, which are usually scented. It’s actually quite easy to make a good hand cleaner. Grab a clean microfiber towel and wet it thoroughly with unscented soap and some water. Pop this into a Ziploc baggie and shove it in your vest or tackle bag. Whenever you may have contaminated your hands, simply massage them with the towel and rinse them thoroughly with water from a bottle or the river.
Conclusions
Is all of this necessary? In all likelihood, any fish-scaring odors will eventually wash off the fly as you fish. I believe this is what happened at Almanor during the Blood Midge hatch. Something had got onto the flies that the fish did not like, and it took about twenty minutes to dissipate. If I’d been smart enough to figure this out, I might have avoided the frustrating skunk. Instead, I missed out on the chance to hook some really big, strong fish. There are enough reasons why we don’t catch such fish. It makes no sense to ignore the smell factor, especially when all you really need is soap and water.
