Back in the innocent world of 2019, I was guiding a group of Norwegian dry-fly purists who came to fish a river I work on in Iceland. This river is big and wide, spring fed straight from a volcano, which means it is cold, harsh, and barren of most insect life aside from sporadic midge hatches — not ideal conditions for fishing a dry fly, but they wanted to try anyway. Knowing this, I took them to a place where a small creek flows into the main stem, one of the few places in the river where I can consistently find rising fish.
Immediately, we spotted a 12-to-15inch brown rising, and the Norwegians started getting excited — apparently that is a sizeable fish elsewhere in the world — but I told them to hunker down and wait. “Let’s watch him and see what else is going on,” I told them. We sat and watched for a few minutes until a shadow emerged from the deeper part of the pool, and in the blink of an eye, a huge wake had come into the shallows, swirled around the rising fish, and then disappeared back where it came from. I looked at my Norwegians, laughed at their shock, and handed them a streamer box.
After that, we walked down to the river, and on the first cast, an over-30inch trout flew out of the water and hammered the streamer. The innocent Norwegian was so surprised that he dropped the rod. Only by a miracle did we save it, but the fish had been lost. After getting plodes, and your mind gets blown — is enough to change your life.
I learned to chase cannibalistic fish in the barren rivers and lakes of my home country of Iceland, but the lessons I learned there apply to California, as well. Predatory fish everywhere turn to eating fish of their own species when the conditions are right, and knowing this can help you target the large, cannibalistic fish in each population. Learning where, when, and how predatory fish target others of their kind will improve your chances of landing a beast cannibal and reduce the time you spend aimlessly blind casting at unproductive water.

The Biggest Fish in the River
Trout, especially predatory trout species such as brown trout, decide to eat other fish and not just insects at some point in their growth. This is especially true in rivers and lakes that may lack nutrients or a stable food source to sustain large fish. Sometimes the best and most nutritious baitfish around is the offspring of the predators themselves. That’s why trout in a lot of river systems that are higher in altitude and that therefore lack salmon smolts, eggs, or any big protein-rich food items turn to eating their babies to sustain themselves.
To reproduce, trout often run up side streams and small creeks to spawn. Once they’ve finished spawning, most of the big fish head back to the main river channel. Small fish often spend the first few years of life in these smaller streams for protection, food, and safety, but during the big storms of the fall and spring, when rain and snowmelt flood the smaller stream, the flows flush the weaker individuals out into the main river, and in these areas, you often find the biggest fish in the river waiting to ambush the now-exposed younger fish.
Often, these smaller creeks will be muddier than the main river, and the big fish utilize this to their advantage. Look for the areas where the color changes from muddy to clearer water — big fish will sit in the darker water and use it as cover for ambushing the fish that get washed into the clear water. Putting your fly right on the edge of the confluence, darting it in and out of the dirtier water, is the best tactic. Expect a big fish to come out of nowhere and slam the fly harder than you’d expect. When a big fish attacks a prey item this large, it isn’t playing around.
In the same vein, when storm systems are absent, think like a smaller fish. Small trout hold in secondary holding spots, because the bigger the fish is, the better feeding lane it gets. To find easy areas for big fish to target smaller fish, look for secondary feeding lanes that are near the prime feeding areas. Sometimes those are smaller rocks next to big rocks and a drop-off, or a mud flat next to a big, deep pool, or a sandbar in the middle of a deep run. Targeting the bigger fish that eat the smaller fish requires knowing where the smaller fish live.
Another clue to where these larger, cannibalistic trout reside: a pool that looks like it should be just perfect to hold a large number of fish, but doesn’t. Although similar pools in the river hold plenty of small to midsized fish, this pool has everything the others have except the fish you’d expect to find there. You nymph through it, dry-fly it, or fish a smaller streamer, all to no avail. This is when you should pull a huge streamer imitating a small trout through it. More likely than not, this pool is home to a huge, scary fish that eats smaller trout and that will slam your streamer. Just be prepared so you aren’t so shocked you’ll drop the rod or have a heart attack.
In one of the rivers I guide on in Iceland, I’ve watched a pattern develop in one of those perfect-looking pools. For the first few years I was there, we’d see only a handful of random big fish, and if we were lucky, catch them. Then, for some reason — most likely the big fish died — the pool filled with smaller fish, and for a few years, it was a haven for small, 12-to-20-inch fish. But in the last two years, the fish have become more and more scattered to the point where this year, there were only two fish left — two very big fish. Most likely, these were fish that moved from a different section of the river, found the pool full of small fish, enjoyed a bit of slaughter, and have now eaten most of the smaller fish and scared off the rest.
How to Catch a Cannibal
Fly choices when imitating small trout as prey items of big trout shouldn’t be overly complicated. The fly pattern is not as important as the action and color. I stick to three main styles of fly actions when I head out on the river looking for cannibalistic trout: a jigging fly, a diving fly, and a gliding fly. In the jigging fly category, a few of my favorites are the Circus Peanut, Dumbbell Feather Game Changer, and the Hog Farmer. For a diving fly, I like the Sex Dungeon, the Big Pig, and the Boogeyman. My favorite of these styles is the gliding flies, mostly since they sit just under the surface, and the takes can be explosive. My favorite gliding flies are the Jerk Changer, Drunk and Disorderly, and any of a million Muddler-style flies. In general, I try to match the color to the fish I’m imitating. With brown trout, for example, that often means patterns with various shades of brown, tan, and olive. But when the water is off color, dark purple, black, and dark blue stand out well. Arm yourself with a variety of flies in each category, and you should be set to chase cannibalistic trout in any conditions you might encounter.

The way I usually choose which style of fly to use is by judging the weather conditions and the water temperature. The exact weather conditions and water temperatures are less important than how they compare to the days preceding the day you’re out fishing. If the temperature has been dropping or is colder than it has been, jigging flies generally seem to do better, because the fish will be tucked in close to rocks, ledges, and shelves. On warmer days and during warming trends, I lean toward the gliding flies, and I use the diving f lies when temperatures are moderate and more or less the same from day to day. But as with everything in fishing, there are no rules, and I’ve caught fish on gliding flies in cold weather and on jigging flies in warm weather. The trend of weather conditions and water temperatures is just a good starting place when heading into a day of fishing, but if you fish a certain style of fly and you’re not seeing the reaction you’re looking for, don’t be afraid to switch it out.
The most important aspect of fishing these bigger streamers is the action you impart to them during the retrieve. You could be in the right place with the wrong fly, but still give it the right action and catch fish. But if you’re in the right place with the right fly and give it the wrong action, that same fish is unlikely to take the fly.
Here’s what I see a lot of beginners doing wrong when I first put a big fly in their hands: they point the rod straight at the fly once it lands and retrieve it with small, repetitive strips. When retrieved like this, these big flies don’t swim or move in a very enticing way, and injured trout that are easy prey don’t swim in a predictable, repetitive manner. An injured fish swims in a jerking, unpredictable motion that kicks and stops, swims and drops. To imitate this movement effectively, you need to use your line hand to pick up slack, but use the tip of your rod to create most of the movement in the fly. Whether that is moving it up and down to jig the fly or side to side to give it jerks on the strip, make it unpredictable, stop the fly, give it random movements, and most importantly, feel what your line is doing. Make sure you maintain tension when using the rod to move the fly. Use your line hand to keep the line tight to the rod tip, creating slack only on purpose in front of the rod. Controlled slack gives the fly room to move, but uncontrolled slack means missed strikes and lifeless flies.
Since the flies used to chase these cannibalistic monsters usually are big, difficult to cast, and especially difficult to pick up and cast over and over, you have to pick your shots carefully. Whenever I arrive at a pool or a piece of water, I sit there for a few minutes examining the current and the bottom structure and seeing if I can spot any fish. Once you’ve located a likely holding spot, pick out the best route your fly should take back to you — that is, where you need to place your line and the path the streamer will take during the retrieve. I want to give the predator the best chance of catching my streamer while still making it look like an injured animal in retreat. If you can, place the fly so it’s against rocks, a bluff wall, a ledge, a sandbar, or anywhere a predator can pin its quarry so that the odds of escape are less. This makes them more likely to commit to crushing the streamer. Your other option is to use the surface film as the pinning point, which I do if a fish has followed my fly but I can’t drag it next to rocks or ledges. Instead, I slowly bring it closer to the surface, and more often than not, the fish will explode on the fly in the surface film.
You might think that since this style of fishing mostly uses sinking lines, that a lot of the casting you do is blind and that the takes will mostly be deep and out of sight. But in fact, fishing a big fly on a heavy line involves sight fishing of a kind, too. It requires you to read the bottom structure well, so as to know where a likely holding area might be, and where best to retrieve the fly through the area in a way that entices the fish to take it. A pair of polarized glasses will help you immensely in figuring out where rocks jut into the subsurface current, where there are ledges, and where a gently sloping sandbar might lie. Some of these areas aren’t as obvious as others, so always spend a bit of time before making the first cast to scan the area.
Another key visual aspect of this style of fishing is reading the body language of the fish. Many times a big fish will follow your fly from a holding spot into the shallows, and seeing the fish’s reaction to the movements of the fly can make or break whether the fly gets hammered or not. If the fish is lazily cruising up behind a jerking streamer, try speeding it up, just as an injured trout would do once it realizes that a huge predator is right behind it. Or if you’re moving the fly fast and a big fish is following, give it a jerk and a stop, then jerk and stop it again, like a fish that’s hurt and running out of momentum. Think like the prey of the fish you’re targeting.
When pursuing large trout with big streamers, I tend to keep my gear relatively simple. My preferred setup is a 9-foot 7-weight fast-action rod with a sink-tip line, my favorite being a sink-tip with a 5 inches per second sink rate and a floating back section. I use it for jigging flies off ledges or wherever there are shallow pockets and areas I need to reach, but it also allows me to pop the flies over the shallows and use the rod tip to manipulate the fly’s depth more easily than with a full sinking line.
The other setup I like is a 9-foot 8weight rod with a full sinking line, which I use more in areas with deep, bowl-shaped pools, deeper runs, and areas where I don’t need to manipulate the fly as much into shallower water and can keep the line deep throughout the whole retrieve. When fishing a full-sinker in these conditions, I like at least a 7to 8-inch-per-second sink rate. Keep in mind that I do all of my fishing from the shore, because I prefer a more boots-on-the-ground approach to chasing fish, and we don’t fish off boats much in Iceland. However, I know the typical American approach is to fish everything from a boat. In that case, a full sinking line might be your number-one line for this kind of fishing, because the retrieve is out to the boat, as opposed to into the shallows, as when you fish as a wade angler.
Catching Cannibal Fever
The life of a fish is brutal. Just imagine what led humans to cannibalism in the past — it wasn’t because things were going well. Predatory animals will do anything to get food when they need it, and to a trout, the Donner Party must have seemed like an actual dinner party. I’ve witnessed schools of small trout migrating down side streams into the main river, only to be annihilated by what were presumably their parents and grandparents. Full-on feeding frenzies reminiscent of tuna slaughtering baitfish in the ocean happen in the right conditions on river and lake systems. And while I didn’t touch on it in this article, I’ve used similar techniques to chase bass in lakes that lack the proper food supply to maintain large bass populations. It’s a fish-eat-fish world out there, and when it comes down to it, nothing is off-limits. Learn to use this to your advantage, and you might just catch some of the largest fish in any given body of water. They didn’t get that big eating midges.