How Muskies Hunt
One of the coolest parts of muskie fishing is the ability to observe an apex predator in its natural environment hunting down its prey. It’s one of the reasons people refer to muskie fishing as such a visual sport: we’ve got ringside seats to how these large predatory fish engage with our lure, sometimes stalking it through multiple figure eight paths culminating in an exciting attack. Scientists aren’t immune to this thrill; there was a study done in the early 2000’s that sought to characterize how muskies hunt. Specifically, the study was interested in how muskies use both their visual and lateral line (the lateral line is used to sense vibrations) senses to track and strike prey.
For each trial, a fingerling muskie was placed in a tank and a small minnow was released. Multiple cameras were used to record and analyze each hunting event from multiple angles. They repeated this many times to generate a wealth of data that characterized how muskies hunt their prey. In almost all instances, the muskies go through a specific sequence when they eat. First, the muskies go through a “target acquisition” phase: they notice the minnow and then turn their bodies toward their prey. They would then engage in a slow stalk toward their target. Finally, when the muskie was close enough, they would lunge rapidly to capture the prey item. To those of us who fish for muskies, this sequence isn’t surprising at all. We often see muskies engage in a short chase to catch up to our lure culminating in the muskie swinging out to one side to “t-bone” our lure. What is more interesting are some of the details associated with the “target acquisition” stage and the ranges at which these different stages happen. The researchers used video footage to analyze these features of muskie hunting behavior as well!
For each hunting event, the researchers carefully measured the following quantities: 1) How distant was the minnow from the muskie when it noticed the minnow, 2) How distant was the minnow when the muskie struck, 3) How far, right or left in degrees of angle, was the minnow from the muskie’s forward direction, and 4) How far, up or down in degrees of angle, was the minnow from the muskie’s forward direction. Now, since the muskies were relatively small fingerlings, I am going to report the distances involved in “body-lengths” of the muskie rather than absolute distances in inches or feet. I think this will make it a bit more universally applicable to we anglers that fish for adult muskies rather than the ranges for these much smaller fingerlings.
The average distance where a muskie would first take notice of a prey item was approximately 1.5 to 2.0 body lengths away from the muskie. Even though the water in the tank was crystal clear and the muskie would have had no problem seeing the minnow from greater distances, the muskies didn’t appear to get into a prey-catching stance until the minnow was relatively close. Let’s discuss this observation briefly, since this information could strongly influence how we present our lures. These muskie fingerlings were all hungry. The researchers made sure that each young muskie hadn’t been fed for some time before conducting a trial. So why didn’t these hungry muskies go into target acquisition mode from further away? I believe the answer is that muskies typically make a cost-benefit analysis about their likelihood of success. If they start a slow stalk from further away, the minnow is probably going to be able to evade their attack. So while the muskie is certainly aware of the minnow from much further away than 2.0 body-lengths, the muskie simply doesn’t recognize the minnow as a potential target until it is closer. At that distance, the muskie will perk up and go into a “target acquisition” mode. Yes, it is possible for an adult muskie to attack from much larger distances than 1.5 to 2.0 body lengths away (you’ve probably even observed this). But the more typical situation is that muskies will ignore presentations unless they are close. Why waste the energy when the chance of success is lower? Muskie fishing is an odds game. Be sure to put the odds in your favor by putting your lures within a few feet of your target.
Proximity was only one facet of the “target acquisition” phase that was studied. The researchers also analyzed the direction from which muskies took notice of their prey. The right-left angle where muskies would notice the prey items were almost all within a sweep of 45 degrees right to 45 degrees left with no preference being shown for right versus left. It is notable that there were a decent number of events (8 of 166) where the right-left angles were quite far away from forward, angles of 120 to 180 degrees (note that an angle of 180 degrees would correspond to directly behind the fish). Similarly, the up-down angle where muskies would notice a prey item were practically all within a sweep of 60 degrees above and 60 degrees below the muskie’s direction of facing. There was also no discernible preference for up angles as opposed to down angles. Please note that last statement because it flies in the face of muskie fishing lore (“Muskies feed ‘up’!”). In these 166 feeding events, there were just as many events where the muskie first noticed its prey when it was below them as there were events where the muskie first noticed its prey when it was above them. While muskies may typically strike from below their prey, they detect prey equally well above and below their direction of facing. As for stalking events where the up-down angle was outside 60 degrees up or 60 degrees down, there were no observations; muskies didn’t engage with prey that was close to directly above them or below them (angles of 90 degrees) during this study. So if you are casting to a muskie that you can see with your eyes, don’t cast right on top of it.
What did the researchers learn about the final strike behavior? The muskies would initiate a rapid lunge to capture their prey at an average distance of about 0.5 body lengths (half a body length) from the prey item. Almost all strikes were launched when the prey item was within 11 degrees of straight ahead for that muskie; that’s a very narrow cone of focus for a strike.
There were a few very interesting exceptions in the strike data. A few of the strikes occurred for distances that were considerably further away from the average strike distance of 0.5 body lengths. These were labelled “far strikes” by the researchers, and they investigated these outlier events very carefully. In every one of these “far strike” cases, the minnow was more than 20 degrees away from straight ahead of the muskie. And in 86% of these cases, the minnow was moving to increase that angle. It’s clear what was happening in these “far strike” cases: the minnows were swimming away from the muskie and the muskie made a desperation strike to try to capture the minnow before it was too far away from that muskie’s “straight ahead” direction. There’s something to be learned from this, and this observation supports muskie lore: if you have a following fish, a rapid change in direction of your lure that takes the lure away from the muskie can trigger a desperation strike. The ideal capture angle from the muskie’s point of view is something within 11 degrees, but if you want to trigger a muskie that doesn’t seem like it's going to strike, swing that lure further than 20 degrees from that muskie’s direction of travel. You might be rewarded with a strike!
Yet the researchers weren’t just interested in describing muskie hunting behavior, they also wanted to know how muskies use their eyes and their lateral line together to hunt successfully. What I’ve just described above was their baseline understanding of how muskies hunt. What the researchers did next was to surgically blind some of the fingerlings. After the fingerlings recovered, they engaged in the same experiment of releasing a minnow into a tank with a blinded muskie. What they found was surprising. Not one muskie engaged in any stalking behavior. They neither turned to face their prey nor did they engage in slow stalk behavior to close the distance to the minnow. However, if the minnow swam within about 0.2 body lengths of the muskie, the muskie would strike. I might add that the rate of successful capture was equal to that of muskies that could see. These fish were using their lateral lines alone to hunt. While they did not use that lateral line to home in on prey and stalk it from a distance, their lateral line allowed them to strike just as successfully as muskies that could see, but only at very close range. What is more, the angle from which these fish struck was even smaller than for muskies that could see (about 7.5 degrees instead of 11 degrees). This data suggests that the lateral line system of muskies is typically used at short ranges. It does not appear to have the capability to allow muskies to stalk prey, nor does the vibrations detected by a muskie’s lateral line call muskies in toward a lure from large distances.
Yet another situation that the researchers tried was to chemically-suppress the lateral line of some of the muskies. The treated fingerlings had their ability to detect vibrations via their lateral line eliminated by this treatment. How did this affect the muskies’ hunting behavior? This group of muskies stalked their prey starting from distances comparable to the unaltered fingerlings. This indicates that muskies use their eyes to notice prey at first and orient to it (they are visual predators). The main difference in their hunting behavior is that they initiated their final strike at a closer distance to their prey than muskies that had full use of their lateral line. This suggests that muskies use their lateral line in the late stages of the prey-capture sequence to more precisely locate that prey item. Lacking information normally provided by their lateral line, they will close the distance even further than normal to ensure successful capture.
Collectively, these observations paint an interesting picture of muskie hunting behavior. It appears that muskies use their eyes to locate and orient to a prey item that they perceive (the lateral line appears to play little if any role in this initial location and orientation stage). The prey item could be above, below, or beside the muskie, but are most easily perceived in an elongated cone in front of the fish, 45 degrees to either side and 60 degrees above or below the muskie. The range at which prey is perceived is generally about 1.5 to 2.0 body lengths from the fish. The muskie will then slowly approach the prey item, using its eyes and its lateral line to track the prey item. With lateral line information coupled with visual cues, the muskie will judge when to strike its prey to maximize its chance of success, typically from about 0.5 body lengths away. If the muskie perceives that the prey may get away before it can close to its optimal strike distance, it may swipe at the prey item from a non-optimal distance. When this happens, it was invariably for angles greater than 20 degrees and almost always when the prey item was increasing that angle by swimming away.
This study of muskie hunting behavior gives us a lot of information about how to maximize the success of our presentations. Hopefully you can use this to put a few extra muskies in your net. Best of luck on the water!
Dr. Bob
