When does the March Brown hatch?

March–May, typically 12:00–15:00. It starts from about 8°C, peaks around 11°C and tails off by 15°C.

What flies imitate the March Brown?

March Brown, March Brown Spider, typically on a #14–12 hook.

How big is the March Brown?

Spinner stage: 9–12mm. That matches a #14–12 hook.

Mayfly · Aquatic insect

March Brown

Rhithrogena germanica

Size

9–12mm

Hook size

#14–12

Hatch window

Season March–MayPeak time 12:00–15:00

Water temperature

11° peak

8°15°

How fish feed on it

Largely academic on most rivers. March brown spinners return in the evening, by which point an early-spring day has usually gone cold enough that nothing is looking up. Worth carrying, rarely worth fishing.

Flies that imitate this

March Brown

March Brown Spider

Ecology

Rivers & stillwaterAlpine riversSpate rivers

Where you'll find this

British IslesPresent
IberiaPresent
The AlpsPresent
ScandinaviaPresent
Continental EuropePresent
Atlantic fringePresent

Present throughout

Identification

Rhithrogena germanica is a European species of mayfly, and is "probably the most famous of all British mayflies", because of its use in fly fishing. It is known in the British Isles as the March brown mayfly , a name which is used in the United States for a different species, Rhithrogena morrisoni . It emerges as a subimago at the end of winter, and can be distinguished from similar species by a dark spot on the femur...

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