The Muskies’ Environment
When I think about patterns that muskies may be following during a particular outing, I often think carefully about the muskies’ environment for the water body that I’ll be fishing. The interaction between muskies and their environment is absolutely going to influence their behavior within that environment. And how muskies perceive their environment will be based on their senses, some of which are highly sensitive and some of which are much less sensitive.
First, let’s consider the visual environment of a muskie. This visual environment is determined by the intensity of the light that is transmitted from the surface as well as the degree to which light is attenuated (absorbed) within the water column. The angle of the sun, sky conditions, etc… will affect the brightness of the light that strikes the surface of the water, of course. But the attenuation of light as it travels through the water is also a very important factor in determining the amount of illumination that muskies experience. Most freshwater lakes and rivers have some degree of “color” due to the production of plankton/algae or the presence of silt and other particulates that are suspended within the water column. Suspended material like this tends to scatter light significantly. If we compare our visual environment to a muskie’s, it is really quite different! Muskies live in a perpetual fog. Even for very bright atmospheric conditions the range to which muskies can see, even with their very dark-adapted eyes, is quite limited: probably fifty feet or less in very clear water, and much less in “dirty” water. Compare that to our experience where we start to get concerned when our visibilities are reduced to a quarter mile or less!
While attenuation due to water “color” is an important factor in the muskies’ visual environment, we should also consider how seasonal changes of sun angle strongly influence the light that hits the surface of the water. We all have a sense that low solar angle (eg. near the times of sunrise and sunset) means lower light conditions compared to when the sun is highest in the sky at noon. But an interesting thing to note is that the noon altitude (height above the horizon) of the sun changes significantly with the season. In December, the sun is only about 20 degrees above the horizon at noon. In June, it can by nearly 70 degrees above the horizon (it never gets to straight overhead, 90 degrees, unless you live in the tropics!). That means in the late season, the light conditions at noon are similar to the light conditions around sunrise and sunset during the mid-summer times. To make a specific example of this, on November 1st in central Minnesota the sun has a noon altitude of 30° above the horizon. On July 1st, that 30° altitude of the sun happens at 8:30AM and 6:00PM. In the late season even the brightest days are similar in light intensity to twilight periods during mid-summer.
Another important factor to consider in all this is muskies’ preferences with regard to illumination. Muskies are a low-light predator, meaning that they prefer a dim environment. Their eyes are specifically adapted to be very light sensitive, and muskies do not have a means of reducing the amount of light that enters their eye. While muskies are certainly capable of operating in bright conditions, their general preference is to be in a low-light environment where they have a predatory advantage.
Next, let’s consider the muskies’ vibrational environment. We humans often think of there being a distinction between sound and vibration, but there really isn’t much difference. Vibration can be “felt”, while “sound” can be heard, but that has more to do with how we detect the vibration rather than any difference in the physical mechanism that produces that vibration. The main distinction is the frequency of the vibration (1Hz is an oscillation per second). Low frequencies (between 1 and 20 Hz) are typically detected as vibrations while higher frequencies (between 100 and 10000 Hz) are detected as sound. In this, muskies and humans are similar! Muskies have two organs that allow them to detect vibrations. Their ears detect the high frequencies, and their lateral line detects the low frequencies. Like light, vibrational signals are attenuated as they move through water. The difference between light attenuation and sound attenuation in water is that sound is much more weakly attenuated than light, meaning that the intensity of vibrations remains strong for much larger distances compared to light.
There is some misconception, however, about the range at which a muskie can detect low frequency vibrations using their lateral line. Scientific studies have shown that the range at which most fish can detect vibrations using their lateral line is on the order of a few feet (one or two body-lengths is the usual figure). High frequency vibrations which register as sound CAN be detected from far away using the muskies’ ears, but the low frequency vibrations (like the main vibration of a spinner blade or the vibration of a crankbait) are not detectable at great range by fish. Rather, the main predatory use of the lateral line is to allow a fish the ability to locate prey very precisely at short range, even when the prey item can’t be perceived visually. This is born out in scientific studies of feeding behavior of blind muskies: when prey items come close to a blind muskie, the blind muskie is just as effective at seizing that prey as muskies that have full use of their eyes!
The vibrational environment of a muskie is strongly affected by lots of noise. Wave action, boat traffic, and even sonar pulses can serve as background noise in the muskies’ environment. While the ultra-high frequencies put out by most sonar are in the inaudible range, these sonar signals are put out in pulses at a given rate. It’s sort of like playing a very high note on a guitar, but playing it at a given rate. While the frequency WITHIN the pulse isn’t audible, the rate at which the pulse is emitted gives rise to the tapping/clicking of your transducer and that most certainly IS audible, both to us and to muskies. What is more, damping factors like the presence of thick vegetation can soften vibrations and attenuate sound. These damping factors should be accounted for when you are seeking presentations that will get noticed by a muskie.
I do not have any specific scientific information about muskies’ preference for a particular sound or vibration. I know there exists some informal evidence regarding certain frequencies, but I’m not prepared to declare those observations as definitive.
There has been some thought put into a muskie’s ability to detect electric fields. The analogy that some folks draw is that sharks have organs that allow the detection of electric fields, and since muskies are sort of the “sharks” of freshwater that they probably have those organs too. However, the organs that sharks have that allow them to detect electric fields (named “ampullae of Lorenzini”) are only present in cartilaginous fishes (sharks and rays) and a few species of freshwater sturgeon. Muskies don’t have them, and therefore muskies don’t detect electric fields any more than we humans do when we get shocked by a static discharge.
However, another aspect of the muskies’ environment that does have a great effect on their behavior is the temperature. Many of us anglers use the temperature measured by our sonar transducer as a stand-in for the temperature of the muskies’ entire environment. However, the water temperature during most times of the year varies a great deal between the surface and the bottom of the lake. Water is a much different medium than air, so our human experience is quite different than what muskies experience. It takes four times as much energy to heat up water to a certain temperature as it takes to heat up the same amount of air. This means that water tends to maintain its temperature, even when air temperatures change rapidly due to changing weather conditions. This “thermal inertia” of water suits the cold-blooded habits of muskies very well. Rapid changes in air temperature are unlikely to change a muskie’s thermal environment very much. And when such a rapid temperature change DOES happen, muskies are able to regulate their body temperature by changing their depth: deeper water is mostly shielded from what’s going on at the surface, temperature-wise.
Even when muskies experience a rapid change in water temperature (like when they swim up from cool deep water to warmer surface water), the muskies’ metabolism does not change on a dime. After all, how long does it take for even a moderately-sized muskie (say, 10 pounds) to have its body temperature change from 65F to 75F due to heat exchange with the warmer water? This is similar to asking how long it would take to defrost a 10-pound turkey by moving it from your freezer to your refrigerator rather than letting it sit on your kitchen counter to defrost. Heat exchange doesn’t happen quickly when the temperature difference isn’t very large!
It appears that muskies prefer water temperatures in the range of about 62F up to about 72F. They seem to have the highest level of activity when they are experiencing these temperatures. While they can certainly be active and aggressive in temperatures outside this range, their preference appears to be between 62F and 72F or so.
Finally, there is the muskies’ olfactory environment: smell/taste. There is not a lot of scientific analysis that has gone into muskies’ olfactory senses, so the only reason I list this here is because of a situation where Steven Paul and I were able to undertake some experiments ourselves. Take these results with a grain of salt, of course! The experiment was conducted during the cold-water period with water temperatures in the mid- to upper-40s. There were three main offerings made to muskies during this experiment: 1) casted artificial lures with no added scent, 2) dead bait (a large intact local forage fish), and 3) cut bait (only the tail of the same type of forage fish as the dead bait). Dead and cut bait was used for two reasons, as opposed to live bait: 1) they didn’t have any motion or action so that their only real attraction was their shape and their smell, and 2) they were available to capture at the time we were fishing (always a plus!). All three offerings were made simultaneously: artificial lures were being cast while the dead bait and cut bait were being presented. All presentations were slow and at roughly the same depth. We observed 30 muskie encounters during the experiment (from 20 different fish), all using live sonar. Of the 30 muskie encounters, 9 involved at least some interaction with dead or cut bait. Of all encounters, 4 of the 30 (13%) happened without engaging the artificial lure. What is more, only 1 of the 30 encounters (3.3%) engaged the cut bait without engaging either the artificial lure or the dead bait.
Obviously, this study could use more data. However, I think some broad conclusions can be drawn about the relative importance of the muskie’s olfactory senses. 26 of the 30 encounters with muskies were with the artificial lure with NO subsequent interaction with the dead or cut bait, meaning that the vast majority of encounters were visual/vibrational encounters with no particular reaction to scent. In some cases muskies would be brought to the dead and/or cut bait by the artificial lure and then would examine that dead/cut bait. Intact forage fish had a clear advantage in interest compared to cut bait. We believe this is due to the fact that the dead bait did at least resemble a prey item; it had the right shape. Even so, there were some encounters with the cut bait that could not be ignored. The conclusion is that muskies do make some use of their olfactory senses while hunting, but that this use will only be at close range and will not necessarily elicit a strike (no muskies actually struck the dead or cut bait during the experiment). This supports the results of another study on muskie strike behavior involving muskies that were both blind and had non-functional lateral line systems. With no ability to see or sense vibration, muskie did not even attempt to hunt. This supports the idea that scent is not a major factor in muskie predatory behavior, but does not rule out scent as a minor contributor to their hunting techniques.
If we think of the muskies’ environment as being most influenced by light, vibration, and temperature, we can begin to understand how muskies use these factors to their advantage as a cool-water, low-light predator. But even more important than the values that we assign to these factors for a particular day or time is how these factors have been changing within the past few days and hours. Are light levels increasing or decreasing? Will this cause muskies to rely more on visual or vibrational cues? Are water temperatures rising or falling? What’s going on with water temperatures beneath the surface? How will the change in these temperatures affect the muskies’ metabolism?
Finally, there is the interplay of factors that can help you consider different patterns of muskie behavior. At times, these individual factors will compete with one another in determining a muskie’s behavior. If surface temperatures are cooling toward a muskie’s preferences (ie into the high 60’s) while at the same time the light penetration values are increasing into the bright range, there is a conflict between preferences. The upper layers of the water column might be thermally desirable to a muskie, but those same layers are exposed to uncomfortable light intensities. When preferences and trends align with one another, definitive patterns of muskie behavior can emerge. But when preferences are in conflict with one another, muskie behavior is typically not as easily predicted (and muskie will tend to be scattered). Hopefully a clear understanding of the muskies’ relation to its environment will help you put together successful presentations!
Best of luck on the water!
Dr. Bob
Musky 360
