From its ice-cold tributaries with aquatic vegetation and gravelly riffles it provides ideal habitat for free swimming and clinging mayflies and stonefilies. The main rivers diverse structure of pool, riffle and silt-ridden eddies provide excellent habitat for the above mentioned species in addition to caddis and the large burrowing drakes like the Hexgenia and Siphlonurus . . . Though Pere Marquette trout are usually very opportunistic feeders, having to brave bitterly cold winters and the onslaught of migrating salmon and steelhead, the dense hatching period can find them selective about imitation and presentation. There are times during the gray drake and Isonychia hatches when there are a ridiculous amount of insects on the water - blanketing every square inch. The Pere Marquette is notorious for complex hatches.
Close inspection is required especially with stonefly and caddis hatching.
The giant Pteronarcys dorsata , or Midwest salmonfly averaging about size 2 to 6, stir up a lot of feeding commotion when they hatch during evening and early morning hours of May through early July. Memorial Day weekend to the middle of June will see the greatest numbers. The lower P.M. has excellent, if not unpredictable hatches of the giant Michigan mayfly Hexagenia limbata . This fabled hatch that stirs up visions of 10 pound browns slashing at giant patterns in the wee hours of the night . . . Late summer fishing is a hodgepodge of minutae and terrestrials with reliable nightly caddis hatches.