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The Mayfly

The Mad Mataura Rise

If you had to pinpoint one thing that has put Gore on the map as the 'Brown Trout Fishing Capital of the World' it would be the Mataura River’s Mayfly hatch.

This is known, both locally and internationally, as ‘the mad Mataura rise’. A ‘rise’ is a phenomenon those who are lucky enough to be at the river's edge during one, will never forget.

“I was in the river up to my shoulders and trout started to rise all around us and I was totally mesmerised by it - it's what I later came to realise is called the 'mad Mataura rise'." Dougal Rillstone, Upstream in the Mataura

What is the Mayfly?

The mayfly is an insect that trout feed on at almost all stages of its life cycle. This provides a challenge for anglers as they need to be aware of and alter their fishing technique to match the changing physical and behavioural habits of the mayfly during its life cycle to be successful whilst fishing.

The Lifecycle of a Mayfly

The four-part development cycle of the mayfly

Stage 1

Larvae, or nymphs as they are referred to by most fishermen, live under the water for almost a full year. Nymphs have tiny claws and cling onto the rocks. Occasionally the nymphs will let go to find better feeding positions to feed and are often washed downstream in highwater flow events such as floods. To catch trout that are feeding on the mayfly at the nymph stage of its lifecycle, an angler must fish with a nymph imitation which is fished sub-surface where the nymphs reside.

Stage 2

After just under a year, the nymphs rise up to the surface of the river and float a short distance where they then shed their nymphal coat and hatch into what is called a dun or subimago, known to anglers as ‘emergers’.

The emerging insect (exo-skeleton) has delicate wings, and a slim tubular body with two or three tails. This process can trigger the ‘anglers' delight’ a ‘rise’. At this stage of their lifecycle, the mayfly is at its most vulnerable and is easy pickings for hungry trout who rise and grab the subimago mayfly’s off the surface.

Stretches of water, that had moments earlier been calm, can become a hive of activity in just minutes with fish rising all over the surface. Anglers will use a dry fly (one that floats) to attempt to imitate the ‘emerger’ (subimago mayfly).

This is a spectacle that is more prevalent on the Mataura River than any other river in New Zealand and is a huge draw card to the area both domestically and internationally.

Stage 3

The surviving duns (subimago) lift off and fly to nearby riverside trees and shrubs for a day or two. Over this period, they transition into full adults (Imago) developing more colours. The angler term for the insect at this stage of the cycle is called a ‘spinner’. This is the only part of the mayfly’s life cycle that the mayfly is not prey for hungry trout.

Stage 4

The final stage of the mayfly lifecycle involves the adult mayfly doing a brief dance which includes bouncing up and down before mating in the air above the rivers and streams. The females then fly upstream and drop their eggs on the surface of the water.

The eggs are carried downstream, and the process starts all over again. Once the adult Mayfly drops her eggs, she falls to the river surface and dies. This last act usually plays out in calm conditions. The most favourable time to fish during this stage is on overcast days, at dawn and dusk.

The number of dead mayflies are easy fodder for hungry trout and can cause a feeding frenzy. Trout take advantage of such easy pickings and often feed with less care and can be more easily approached by anglers.

This can create a double-edged sword for the angler whose fishing fly is now competing with numerous dead mayflies’ for the trout’s attention.

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