Connecticut Fly Fishing Hatches: A Season-by-Season Hatch Chart
Matching the hatch is the most satisfying discipline in fly fishing — and one of the most misunderstood. You don't need to memorize 200 Latin names. You need to understand what's hatching in the water you're fishing and when. Here's the Connecticut-specific hatch calendar that covers the major events on the Housatonic TMA and Farmington River.
The Concept of Matching the Hatch
Aquatic insects (mayflies, caddisflies, stoneflies) spend most of their life as nymphs underwater. When they're ready to hatch, they rise to the surface, split their nymphal shuck, and emerge as adults. This emergence — the hatch — is when trout feed selectively on a single insect species and size. During a heavy hatch, trout may refuse anything that doesn't closely match the emerging insect. Matching the hatch means identifying what's hatching (species and size), having a fly that approximates it, and presenting it appropriately (dry fly for adults, nymph for underwater stages, emerger for the transitional stage). You don't need a perfect match every time — you need a good-enough match presented drag-free.
March–April: Quill Gordon and Hendrickson
Quill Gordon (Epeorus pleuralis): the first significant early-season hatch in CT, typically beginning in late March. Size 12–14 dry fly. Dark brown body, gray wings. Emerges in riffles during afternoon on cold days (water 45–50°F). Use a Quill Gordon dry fly (size 14) or a soft-hackle wet fly below the surface during emergence. Hendrickson/Red Quill (Ephemerella subvaria): the most anticipated CT spring hatch. The Housatonic TMA Hendrickson hatch typically peaks in mid-to-late April, occurring mid-afternoon when water temperature reaches 50–55°F. The hatch can be spectacular — fish rising everywhere, dry fly fishing at its best. Dry fly: Hendrickson pattern (size 12–14) or Parachute Adams as a general match. Emerging insects: CDC Emerging Dun. Spent spinner: Red Quill Spinner after the hatch ends.
May–June: Sulphur and March Brown
March Brown / Grey Fox (Maccaffertium vicarium): overlapping hatches from late April through June. Size 10–12 dry fly. Brown/olive body. Hatches throughout the day in overcast conditions. A Grey Fox soft hackle works well during the hatch. Sulphur (Ephemerella dorothea): May through June, often peaking in late May on CT rivers. Size 14–18 pale yellow/sulphur colored body. Evening hatch — often most intense in the last hour before dark. The Farmington River Sulphur hatch can be outstanding. Sulphur patterns: CDC Sulphur Dun (size 16), Parachute Sulphur. Spinner: Sulphur Poly Spinner. Light Cahill: similar timing to Sulphurs, similar presentation. Size 14, cream/tan body.
June–July: Trico and Caddis
Caddisflies (various Hydropsychidae): the most abundant insect in CT rivers by volume. Caddis hatch in late spring and summer across a wide range. Size 14–18, tan, olive, or gray. Evening hatches are most intense. Elk Hair Caddis is the universal go-to pattern. Film spinner (spent caddis): fish the surface film at dusk during spinner falls. CDC Caddis spent wing is effective. Trico (Tricorythodes): tiny size 18–24, early morning spinner falls from July through September. The white wings of the male spinner and the spent female are the trigger. Fish need to rise actively before you can identify this hatch by the impossibly small insects on the water. Use a Trico Poly Spinner (size 22) on 7X tippet. This is advanced dry fly fishing — the presentation must be perfect.
August–September: Late Season Hatches
Blue-Winged Olive / BWO (Baetis species): year-round in small sizes, but particularly significant in August–September and again in October–November during cloudy, drizzly conditions. Size 16–22 olive body, gray wings. The classic 'bad weather hatch' — BWOs often hatch most intensely on overcast, cold, rainy days when you might not think about going fishing. Use a Parachute BWO (size 18) or CDC BWO Emerger. Isonychia / Mahogany Dun: late summer and early fall. Size 12–14, dark burgundy/brown. The best dry fly match is an Isonychia Dry. White Fly (Ephoron leukon): late August–September evening hatch on some CT rivers — a white mayfly that hatches in significant numbers at dusk. When present, it drives fish to the surface aggressively. White fly dry pattern in size 14–16.
October–November: October Caddis and BWO
October Caddis (Pycnopsyche): large orange/amber caddis, size 8–12. Late September through October. Excellent hatch that drives feeding activity in fall. Elk Hair Caddis or stimulator in orange works well. Adult stage is large enough to use as a streamer-style wet fly. Blue-Winged Olives: return in force during overcast fall days (October–November). The same BWO patterns from summer apply. Fall fish are feeding more aggressively in preparation for winter — a well-presented BWO during the October hatches can produce exceptional fishing. Stoneflies: some large stoneflies emerge in fall and winter in CT rivers. Their nymph patterns (black stones, size 6–8) fished deep are effective year-round but particularly in fall when adults are present.
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