Published July 01, 2011, 12:00 AM

Hot weather triggers mayfly hatch on most lakes

The warm weather usually associated with summer finally arrived in the Bemidji area just in time for the Fourth of July Weekend.

By: Paul Nelson, Bemidji Pioneer

The warm weather usually associated with summer finally arrived in the Bemidji area just in time for the Fourth of July Weekend.

The sudden warm-up triggered the mayfly hatches in most of the lakes. The mayfly hatches were delayed this year by all the cold weather and rain.

Both predator and prey species of fish will head for deeper water to take advantage of the explosion of food taking place in the mud basin of most lakes.

The large lakes like Winnibigoshish, Leech, Cass, Pike Bay and Bemidji usually have the most mayflies because of the vast areas of mud basin surrounding most of the mid-lake structures in those lakes. The lakes with the most mayflies are also usually the lakes with the largest populations of walleyes and perch.

Many of the smaller lakes have a few mayflies but there are usually far fewer mayflies and other insects hatching because of the limited amount of mud basin.

The insect hatches have already slowed fishing in most of the larger lakes. Many walleyes are in the process of changing locations from shoreline connected structure to mid-lake structure. That movement was also delayed this year because of the cold water conditions.

Many anglers have been using live-bait rigs with leeches or night crawlers for walleyes. Both leeches and night crawlers resemble large insects and are more of a treat to walleyes than minnows, which are more of the main course. This usually means walleyes with full stomachs are more likely to take a leech or night crawler rather than a minnow.

Walleyes feeding on emerging mayflies often suspend, so anglers usually have to use longer leaders (six to 10 feet or more) to get their baits into the same zone as the walleyes. Injecting air into night crawlers or leeches will help float them off the bottom.

Walleye anglers have been finding a few fish remaining on shoreline structure in the cabbage weeds but many walleyes have been moving into deeper water to take advantage of the insects hatching out of the basin. Walleyes will feed on the insects and also on the minnows and other smaller fish that are also feeding on the emerging mayflies.

Mayflies live in the mud in the basin of the lakes as larvae for about a year. When they are mature they emerge and migrate to the surface in huge clouds that are visible on sonar.

Most mayflies rise to the surface of the lakes at night when the water is usually calm. They float on the surface until their wings are dry and then fly away to complete their life cycle. .

Mayflies don’t have mouths and won’t eat while they are in the adult phase. Their sole purpose is to lay their eggs into the lakes before they die. Most mayflies only live a few days during their adult phase.

If the weather stays hot the mayflies will hatch more quickly and be done sooner. If the cold weather returns the mayfly hatches will be more drawn out and take longer to complete.

Among the other signs that summer is approaching is the blooming of the algae. The algae gather in tiny globs in the water, which will eventually tint the water green and reduce visibility in the lakes.

The water in the lakes is still very clear so the fish in shallow water are spooky when the winds are calm and the skies are clear. Most shallow fish want some wind and overcast skies before they will bite.

Walleyes using deeper water will often move closer to structure when they feed and then move back down the drop-off when they are resting. Anglers can often tell how active the walleyes are by how deep they are and how close to the bottom they are hanging.

Paul A. Nelson runs the Bemidji Area Lakes Guide Service. He can be e-mailed at panelson@paulbunyan.net.

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