Description
Mayfly Nymphs – Life Below the Surface
Mayfly nymphs are the engine of the river and lake ecosystem. They are active year-round and represent a constant, reliable food source for trout and grayling from early spring to late autumn. To fish a mayfly nymph successfully, you must understand their behavior. They are categorized into three main types: Digging, Swimming, and Clinging nymphs, each adapted to specific environments.
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Digging Nymphs: Found in lakes and slow-moving river sections with soft or sandy bottoms. These include some of the giants, like the Green Drake (Ephemera danica).
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Swimming Nymphs: Agile and active, these are found in both still and moving water. They are often drift-feeders, like the Claret Dun (Leptophlebia).
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Clinging Nymphs: The "bodybuilders" of the mayfly world. Short, compact, and powerful, they live on rocks in the roughest currents, like the Yellow May Dun (Heptagenia).
Our Commitment: Anatomical Accuracy & Performance Since mayfly nymphs spend most of their lives tucked away near the bottom, they only become truly vulnerable when they lose their grip, drift to find food, or begin their journey to the surface to hatch. This is when the fish strike.
Our commitment is to provide imitations that match the specific silhouette and behavior of these three categories. By using J:son’s unique materials, we create nymphs with the correct proportions, lifelike legs, and balanced weight.
The Barbless Micro-Swimmer – J:son Mayfly Nymph 4 Black (Hook #14 BL) The Black Nymph 4 BL is our most delicate swimming nymph imitation, specifically designed for technical fly fishing and conservation-minded anglers. Tied on a barbless (BL) size #14 hook, this fly matches the smallest species within the Baetidae and Leptophlebiidae families. On this small scale, the nymph represents insects that turn dark, almost jet-black, just before ascending to the surface to emerge.
Using a barbless hook not only complies with regulations in many catch-and-release waters but also ensures a deeper, cleaner hookset and easier release of the fish. Despite the small size, this nymph retains J:son’s hallmark anatomical realism, featuring a segmented body and lifelike legs. Its sharp black silhouette provides high contrast in various light conditions, making it an essential pattern for selective trout and grayling in clear mountain streams or calm lake margins. Best fished on a fine tippet with a dead-drift or subtle, minute pulses.