
If by “aggression” you mean a more aggressive fish response, this card is actually the opposite: a subtle mayfly nymph for selective trout. Big Y Fly Co Barr's Emerger BWO - Glass Bead is best when trout are keyed on Blue-Winged Olive insects and want a natural, low-flash presentation in clear, pressured water.
Fish it dead-drift, not with an active retrieve. Use it as a lead fly in a two-fly rig or trail it behind a heavier attractor to get it down while keeping the presentation subtle. Best in slow backwaters, spring creeks, and tailwaters with a slow sink and natural drift.
Switch to a more aggressive attractor pattern if fish are not responding to a dead-drift, if water is stained, or if you need more visibility and movement. If trout are chasing rather than feeding selectively, a subtler emerger like this is usually not the right first choice.
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