Frank Sawyer’s Killer Bug is deadly in streams of chalk. Although it is designed to catch large numbers of grayling, it can also be effective against trout. The Killer Bug Technique is unique, but anyone who is willing to learn can learn it quickly.
As far as I know, no one is really sure why the Killer Bug is so effective. My grandfather, the late Frank Sawyer, originally designed it to mimic the freshwater shrimp Gammarus Pulex, but it is just as effective in the water without the crustacean, or when tied several times larger than natural. The Killer Bug is generally taken when it is made to ‘swim’. Most of the time, this will be in the ‘shrimp zone’, but sometimes it can be carried above this area while seemingly ‘swimming’ to the surface. Since shrimp only inhabit the bottom of a chalk stream, it’s hard to see why the fish would take an artificial shrimp to the wrong place. Pigs can fly, but who would eat a bacon sandwich if it were floating several inches above the table? My grandfather suggested in ‘The Nymphs and the Trout’ that the swimming insect resembled a sedge making its way to the surface. Some well-known fishermen claim that the Killer Bug looks like a worm or larva that has fallen into the water, others say that it looks like a food pellet for stored fish. I’ve even seen small pike follow a killer bug through the water (though never take it), so it might look like a minnow in some conditions.
The widespread malaise of chalk streams and declining fly abundance is a clear cause for concern, but we sometimes forget that perhaps as much as 80% of a trout’s food is eaten below the surface. Unless we are lucky enough to be fishing during hatching, trout may not be as interested in dry fly. This presents a problem. Like most fishermen, I fish when I can find the time, hatch or not hatch. Fortunately the fish have to eat. If there are no flies on the surface, or they seem to ignore whatever flies and nymphs are hatching, then they must be eating something else. It is often the freshwater shrimp.
It is always surprising how often fishermen fail to detect the large numbers of clearly discernible fish in a stretch of water. The first step in fishing for Killer Bug is to attempt to operate where the fish are visible. It is not essential, but it makes the technique easier and more fun.
Upper Avon, where I enjoy most of my fishing, has a grayling population that far exceeds that of trout. It is very tempting to ignore the grayling and keep moving upstream in search of trout. My grandfather had a phrase for this: “Give up gold to fish for tinsel.” Graylings are a true wild fish and they are a pleasure to catch. Not only do they provide a decent sport, but they taste good and are more abundant than trout. On many occasions I have been fishing for grayling and a previously hidden trout has come out of hiding to take my Killer Bug. For the angler out of practice, or those of us who fish infrequently, grayling is an ideal way to start the day and polish up those Killer Bug skills before tackling the big trout a few hundred yards upstream. My father and I sometimes spend a day fishing grayling with a Killer Bug. The goal is to catch each grayling on a sandbar before continuing. It is not uncommon for us to land more than 50 grayling in 3 or 4 hours of fishing.
The most important part of the Killer Bug technique is getting the bug to swim the right way in the right place. To achieve this, the insect must be allowed to sink to the bottom of the river and then it must be made to swim to the surface in a smooth and natural way. Where to start the swimming movement will depend on the location of the fish and the current flow. The point at which the swimming movement begins is known as the trigger point. The cast has to be far enough upstream from the trigger point so that the insect can sink to the correct depth before the swimming motion begins. This point is known as the launch area. Here’s the good stuff. As long as there are no weeds or obstructions, the insect can bounce off the bottom for a certain distance before beginning the swimming motion. This reduces the requirement for a precise and delicate casting, as anywhere upstream from the casting area will be satisfactory. All the angler has to do is allow the insect to bounce along the river bed until it reaches the trigger point and then begin the swimming motion by slowly lifting the tip of the rod and maintaining a tight line. The peculiarities of undergrowth, obstructions and currents can occasionally prevent the angler from performing this technique, and fish have a habit of feeding in awkward places, but there will be many places in the chalk stream where this technique can be used. . Trout can sometimes be startled by an insect rolling along the river bed, but grayling rarely worry.
The trigger point is easy to calculate. To be most effective, the insect should be made to start swimming 1 to 2 feet in front of the target fish. This makes the trigger point 2 feet in front of the target fish if it is located at the bottom of the river, or higher if it is feeding closer to the surface. The launch area will depend entirely on the depth of the water and the current speed. Unless it’s a particularly deep pool or a very fast current, 4 feet is a good starting point, but trial and error will ultimately be the deciding factor. If it is clear that the bug has not sunk to the bottom before the trigger point, move the launch area higher.
Knowing when to attack is without a doubt the hardest part of Killer Bug fishing. I have seen a fisherman draw his line and cast again happily without realizing that several fish have caught and then spit out the assassin bug. The hit is easier when the angler can clearly see the insect and the fish, but can also be performed when only the fish is seen. It is even possible to use the line at the point where it enters the water as an attack indicator and the best Killer Bug anglers can be successful attacking only on instinct.
With good light conditions and clear water, it is very easy to see insects in the water and even easier to see fish. What could be simpler than watching the Killer Bug enter the fish’s mouth and then attack it? Unfortunately, fish spit out insects very quickly and the act of striking can be time consuming in comparison, particularly if the fish is too far away or there is a lot of slack in the line. That’s why Killer Bug fishing is more successful nearby; eliminates the need to anticipate fish action. If the fish is more than 15-20 feet away, the hit should begin before the fish has caught the insect due to the time lag between the hit and the hook setting. Fish rarely latch onto a killer bug.
It is also relatively easy to judge when an insect has been caught by looking at the fish. This is the most common technique, as it is very difficult to keep observing a small Killer Bug as it sinks several feet away. Although you may not be able to see your mistake, you should have a reasonable idea of where you are in the river. Any fish that runs to that rugged spot and then stops may well have caught. This is the time to attack. If your cast has been very precise, your fish may not have to move that far to carry your bug. In this case, look for a flick of the tail, a jerk of the head, or a slight upward tilt. Ironically, the inaccurate cast, which causes a fish to move towards its insect, is sometimes more successful as it can be easier to identify the shot.
Occasionally it is not possible to see the fish or the Killer Bug. Maybe the river is too dirty or the light is wrong. Under these conditions, it is worth keeping an eye on the line at the point where it enters the water. When the insect is swimming, watch for minute, almost imperceptible marks or movements at the point where the line dips below the surface. If you see such an indication, knock. Every now and then the fish will take with a bang and there will be no question of the act, but this is rare.
Fishing just by instinct is the most difficult technique, but it’s really just common sense and experience. Common sense dictates that the Killer Bug is more likely to be caught in the first few seconds of swimming action while in the “shrimp zone.” Experience tells us that grayling and trout are predictable; most fishermen know where they can feed. Combining common sense and experience leads to an instinct for where and, more importantly, when you are most likely to catch a fish. Hitting at this point can result in success. It’s certainly worth a try if none of the other techniques can be used.
No matter how you caught the first fish, it is important to “file” the insect, the nylon cast, and the leader. Fish slime has several properties that are extremely helpful to the Killer Bug angler. First of all, the slime makes the bug taste more natural. This takes longer for the fish to spit out the artificial, giving them valuable extra milliseconds to attack. The slime from the cast “wets” the nylon and allows it to slide through the water more easily. This causes the insect to sink quickly and force is imparted along the line with less resistance to water. Lastly, the slime masks distinctively human odors, such as soap or tobacco, that remain in tiny fingerprints on everything we touch.
There are no promises in fly fishing, but a competent Killer Bug technique on the chalk stream is the closest to a guarantee that can be achieved while still abiding by club rules. The technique is simple, effective, a lot of fun, and once mastered, it is never forgotten. The Killer Bug’s biggest attraction is possibly its versatility. In today’s hectic lifestyle, with the associated pressures on valuable fishing time and the marked decrease in fly life and surface feeding, it is perhaps more relevant to modern anglers than ever. After more than 50 years of distinguished service, Killer Bug remains a deadly enigma, and will remain so for a long time to come.