Frank Sawyer’s Killer Bug is deadly in chalk streams. Although designed to catch large numbers of grayling, it can also be effective against trout. The Killer Bug technique is unique, but can be quickly learned by anyone willing to learn.
To my knowledge, no one is really sure why Killer Bug is so effective. My grandfather, the late Frank Sawyer, originally designed it to mimic the Gammarus Pulex freshwater shrimp, but it is just as effective in water without the crustacean, or when tied several times larger than its natural size. The Killer Bug is usually taken when made to “swim”. Most of the time this will be in the “shrimp zone”, but sometimes it can be taken 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 fish would take an artificial shrimp in the wrong spot. Pigs can fly, but who would eat a bacon sandwich if it was floating several inches above the table? My grandfather suggested in ‘The Nymphs and the Trout’ that the swimming insect resembled a sedge that makes 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 it looks like a pellet of food to seed fish. I’ve even seen small pike follow an assassin bug through the water (although I never take it), so it might look like a minnow in some conditions.
The widely reported chalk current discomfort and decline in fly abundance is a definite cause for concern, but we sometimes forget that perhaps as much as 80% of a trout’s food is taken below the surface. Unless we are lucky enough to be fishing during a hatch, the trout may not be as interested in the dry fly. This presents a problem. Like most anglers, I fish when I can find the time, with or without a hatch. Fortunately the fish have to eat. If there are no flies on the surface, or they seem to be ignoring any hatching flies and nymphs, then they must be eating something else. It is often the freshwater shrimp.
It is always surprising how often anglers fail to spot the large number of clearly discernible fish in a stretch of water. The first step in Killer Bug fishing is to try to operate where the fish are visible. It’s not essential, but it makes the technique easier and a lot more fun.
Upper Avon, where I enjoy most of my fishing, has a population of grayling that far exceeds that of trout. It is very tempting to ignore the grayling and continue upstream in search of trout. My grandfather had a phrase for this: “Give up gold to fish for tinsel.” Grayling is a true wild fish and a joy to catch. Not only do they provide worthy sport, but they taste good and are more plentiful than trout. On many occasions I have been fishing for grayling and a previously hidden trout has darted out of hiding to grab my Killer Bug. For the unpracticed angler, or those of us who fish infrequently, grayling is an ideal way to start the day and hone those Killer Bug skills before tackling big trout a few hundred yards upstream. My father and I sometimes spend the day fishing for grayling with an assassin bug. The objective is to catch all the grayling on a school before continuing. It is not uncommon for us to land more than 50 grayling in 3-4 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 made to swim to the surface in a gentle and natural way. Where to start the swimming motion will depend on the location of the fish and current flow. The point at which the swimming motion begins is known as the trigger point. The cast must be made far enough from the trigger point that the insect can sink to the proper 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 some distance before beginning the swimming motion. This reduces the requirement for precise and delicate casting, as anywhere upstream of the casting area will be satisfactory. All the angler has to do is allow the bug to bounce along the riverbed until it reaches the trigger point and then begin the swimming motion by slowly raising the rod tip and keeping a taut line. Peculiarities of brush, obstructions and currents can occasionally prevent the angler from carrying out this technique, and fish have a habit of feeding in awkward places, but there will be plenty of places in the chalk stream where this technique can be used. . Trout can sometimes be triggered by an insect rolling across the riverbed, but grayling almost never have a problem.
The activation point is easy to calculate. To be most effective, the insect should be made to start swimming 1-2 feet in front of the target fish. This causes the trigger point to be 2 feet in front of the target fish if located on the bottom of the river, or upstream if feeding near 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’s clear the bug hasn’t 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 anglers draw on their line and happily recast without realizing that several fish have taken and then spit out the killer bug. Hitting is easiest when the angler can see the insect and fish clearly, but it can also be done when only the fish is visible. It is even possible to use the line at the point where it enters the water as a strike indicator and the best Killer Bug anglers can be successful hitting on instinct alone.
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? Unfortunately, fish spit out insects very quickly and the act of striking can be comparatively time consuming, especially if the fish is very far away or there is a lot of slack in the line. That’s why Killer Bug fishing is more successful up close; eliminates the need to anticipate fish action. If the fish is more than 15 to 20 feet away, the hit will need to start before the fish has caught the insect due to the time between the hit and the setting of the hook. Fish rarely get hooked on an assassin 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 watching a small assassin bug as it sinks several feet away. Although you may not be able to see your bug, you should have a reasonable idea of where it is in the river. Any fish that runs into that rough spot and then stops may well have caught it. This is the time to attack. If your cast has been very accurate, the fish may not have to move as far to catch your bug. In this case, look for a flick of the tail, a sudden movement of the head, or a slight upward tilt. Ironically, inaccurate casting, which causes a fish to move towards its bug, is sometimes more successful, as it can be easier to identify the catch.
Occasionally neither the fish nor the Killer Bug can be seen. Perhaps the river is too dirty or the light is not right. In these conditions, it is advisable to monitor the line at the point of entry into the water. When the bug is swimming, watch for small checks or almost imperceptible movements at the point where the line dips below the surface. If you see such an indication, hit. Occasionally the fish will catch it with a hit and there will be no mistake on the spot, but this is rare.
Fishing on instinct alone is the most difficult of techniques, but it’s really just common sense and experience. Common sense dictates that the Killer Bug is most likely to be taken in the first few seconds of the swim action while in the ‘shrimp zone’. Experience tells us that grayling and trout are predictable; most fishermen know the places where they usually feed. The combination of common sense and experience leads to an instinct of where and more importantly when you are most likely to catch a fish. Hitting at this point can result in success. It’s definitely worth a try if you can’t use any of the other techniques.
No matter how you caught the first fish, it’s important to ‘get down’ the bug, the nylon cast, and the leader. Fish slime has several properties that are extremely helpful to the Killer Bug angler. First, the slime makes the bug taste more natural. This makes it take longer for the fish to spit out the artificial, giving it valuable extra milliseconds to attack. The slime from the plaster ‘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 the water. Lastly, slime masks distinctly human odors, such as soap or tobacco, which leave tiny traces on everything we touch.
There are no promises in fly fishing, but competent Killer Bug technique on the chalk stream is as close as one can get to a guarantee while still adhering to club rules. The technique is simple, effective, a lot of fun and, once mastered, it is never forgotten. Arguably the biggest attraction of the Killer Bug is its versatility. In today’s busy lifestyle, with the associated pressures on valuable fishing time and the marked decline in fly life and surface feeding, it is perhaps more relevant than ever to modern anglers. After more than 50 years of distinguished service, the Killer Bug remains a deadly enigma, and may it remain so for a long time to come.