Bug of the Month: The Leech

“Trout love leeches. No doubt about it.” ~~ Phil Tereyla

Our Bug of the Month for February is the leech. Covey guides, Phil Tereyla and Brian Hilbert, offer up some suggestions for fishing with this productive pattern. 

Brian Hilbert says that it’s the “most consistent pattern on my rig regardless of time of year. Fish them in winter, spring, summer, and fall.  There may be an ebb and flow with fish eating them, as with most bugs, but they are a consistent food source.”

About The Leech

The leech is a carnivorous worm that feeds on little aquatic insects.

You’ll find them under the rocks, or living in the mud, or attached to logs in our fisheries. When they get dislodged or venture out from those protective structures, they will drift and swim in the current.

Most often they’ll be in dark brown, or black, but there are quite a few olive-colored leeches in our tailwaters. They can take on the color of the vegetation.

Leeches are tough to measure.  They may range ½ inch to 2.5-3” long. When they are swimming, they can stretch themselves to around 3” long.  If you watch them swim, you’ll get a different perspective on their size compared to flipping over a rock or the bottom of a log and checking them out. Because of their size, they are a great food source, full of calories compared to smaller insects in the water.

Phil Tereyla has his clients observe the leech’s swimming behavior down on the Arkansas tailwater. “It’s pretty incredible how many leeches are on the Ark.  Walk around in the mud and the sediment for even a couple of steps and then let the water settle. You’ll see two or three leeches swimming around when the water clears.”

Their movement is very distinctive because the leech is an invertebrate. Somewhat surprising, the leech is also muscular. With their deceptive strength, they can extend and contract making them appear almost like inch worms propelling themselves through the water.  Phil says “they’re kind of like an inverted snake when they ball up and then stretch out.”

Leeches are a year-round food source because they are “not water-temperature dependent.”  You’ll see more leeches in the water when the flows are higher. They’ll get displaced from run-off, knocked loose from logs or rocks.  (Which means, too, that they could be our focus bug in the spring!)

Fishing the Leech

Because the leech is a bigger food source, trout will tend to hunt for them more. They’ll search them out in low light scenarios like the early morning or in the evening.

Leeches will emerge from under rocks or structures along the bank and drift with the river or stream’s current.

Phil and Brian have different approaches for presenting the leech to hungry trout. Their different strategies show the versatility in fishing this pattern. Anglers will need to experiment with their rig to see what works for their fishery. 

Brian’s approach is “a little out of the ordinary. I’ll fish a weighted jig-style leech on the bottom and then unweighted nymphs above that. Even though this rig drops the leech closer to the bottom of the riverbed, I’ll have clients finish their drift and swing it all the way to the bank. Give it a couple of twitches as it rises in the water closer to the bank. That swing and then some movement produces pretty ferocious strikes.  It’s consistent enough that it’ll result in a grab or two.”

Phil agrees that any tactic that gives the leech an undulating motion can result in aggressive takes. It mimics how they swim and move through the water. 

Dead Drift the Leech

Phil and Brian agree that dead drifting the leech patterns can be very productive. While it is sometimes tempting to strip or do something with the leech pattern, allowing it to dead drift with the current can get plenty of takes.

 “Dead drifts give fish the opportunity to eat something big and meaty without having to do much work,” Phil says. “They don’t have to chase them down.”

To give them a little movement, “you can definitely throw a mend or allow the current to catch your line so that it swings a little bit. Then give it a mend and slow it down where it is drifting more naturally.  Those adjustments can elicit a more aggressive take because the motion triggers a fish to eat it.” 

The leech can also serve as a great attractor. Maybe the fish are keyed in on BWOs, PMDs, midges.  Even though the fish might ignore the leech, it will get them excited.  Sometimes fish will eat leeches until a hatch is heavy, and then they’ll switch to the hatching insect.  And once the hatch ends, fish will often switch back to eating the leech.

In February, fish are starting to move around. They are actually in pre-spawn mode. Fish are well aware of what is coming.  It’s the natural cycle of things.  As Phil says, “They know that the grueling spawning ritual is ahead. They are going to try and pack on some extra poundage because of how much energy it takes for them to spawn. In these coming weeks, fish will be searching out those bigger meals.” Because of this behavior, the leech rises to the status of “bug of the month.”

Tying the Leech

When it comes to tying, Brian says, “I almost exclusively fish Landon Mayer’s mini-leech because it is such a spot-on imitation. I don’t over-complicate tying it. I tie them in 16s and vary my bead size. Brown patterns and olives are the mainstays in my fly box. The profile and movement of the mini-leech is so good that it sort of makes color a little less relevant.”

Phil will tie up and carry leech patterns from a size 12 to an 18.  He ties his own leather leech pattern (available soon from MFC).  His pattern is “flat and streamlined. And I keep them about an inch to 1.5” long.”

For Phil, his color choices are black, olive, and brown.  The black patterns will serve specifically to imitate a leech.  Other colors, though, can be more enticing. “The brown or rust-colored pattern can work as a leech or a worm. The olive one I tie can work as a leech or as a big cranefly larva.”

Final Thoughts

While their strategies for fishing the leech and their approaches for tying the patterns may differ, Brian and Phil agree: “Leeches are one of my favorite patterns to fish.” 

Watch this space and our YouTube channel throughout the month for videos on how to fish the leech and how to tie up some of the patterns.