Vermont, July 2013.  When fishing, you never know what will happen and on one of “those” days, nothing happens, not even a lowly refusal of the various flies you cast to the fish you have not seen and then with luck, you stumble into a “presto change-o” experience.

Even though the long deep pool was shaded and usually offered up one and sometimes more fish, either smallmouth bass and/or rainbow trout, pure nothing was going on on this August afternoon. Some fishers are surprised that the same pool could yield both warm and cold-water fish. Those of us who fish the Connecticut River watershed know that on the lower reaches of several tributaries, taking these different species of fish happens depending on the weather, flows, water temperature and time of year.

This pool pretended, convincingly, that it was devoid of fish life leaving the only option; move on upstream to the next pools. Despite the fishers usual unfounded hope that upstream will be better, on one of those days the results after two hours of fishing were no runs, no fish and no errors and not only were there no fish to be had but a lightning bolt announced a thunderstorm moving in from the west. Rain is no problem when fishing, you are either wet already, about to get wet or are wearing chest waders and adding a rain coat means you are completely wrapped in waterproof material.

The rain poured and with lightening streaking the sky it was no time to be in the river. When you want to leave this particular reach of river, you have to turn around and walk back downstream. You can hop up onto the shore and follow an animal trail most of the ways through a regrowth stand of trees back to the original pool.  You then cross the pool and follow the path out to the road.

The walk back took 15 minutes longer than the thunderstorm lasted and crossing the original pool, two pleasant events happened simultaneously. The sun came out and fish announced themselves as they started to rise, splashing as they fed on some kind of insect on the surface of the water. There had to be at least six different fish rising all down the detritus line flowing from the head to the tail of the 50 foot long pool. It did not seem possible that this was the same fishless pool abandoned only two hours earlier.

It is one thing to see rising fish but if you intend to catch those fish, you have to identify the insect they are feeding on; in this case, it was obvious. There was a ghostly black swarm of flying ants at the head of the pool. The rain had stimulated nest queens to go on their mating flights. The mating swarm meant that a nest and likely several others near it had reached their population limit, had some resources to spare so produced winged male drones and the rain cooled air gave the signal to the queens that now was the time to start other nests.

The queens mate with the male drones in flight. This phenomenon typically occurs in several colonies simultaneously. This happenstance avoids inbreeding and allows the ants to overwhelm predation with sheer numbers.  Mating flights by several nests might appear to be a timed event but usually it is nothing more than a common response to similar nest resources, temperature, humidity, windspeed and time of year.

Mating takes place in bursts that seldom last more than a few hours. The males die and the mated females disperse to establish new nests. The winged queen sheds her wings after mating and then crawls along the ground searching for the new nest location. Her body absorbs the now useless wing muscles to provide a source of nutrients during the early stages of nest development.

The males exist for the only one purpose, inseminating the queen and cannot even feed themselves during their short lives.  Males quickly die after mating. Predators of all kinds take note of the mating swarm, and it is common to see dragonflies and birds feasting on the swarming ants. In this case, the dying males falling on the water were providing a feast for the fish.

During the summer, this situation is why flyfishers have flying ant patterns in their fly box.  As the fish continued to rise to the depleted drones falling on the water, the artificial flying ant imitation did the trick. Three fish later, all caught on the flying ant pattern, the ant swarm either relocated or just stopped massing but it was gone from the pool. So were the rising fish. The quick disappearance of the fish reminds one of “Now you see them, now you don’t” but even on one of those fishless days, there are presto change-o moments to savor.

David L. Deen, River Steward for the Connecticut River Watershed Council. CRWC is celebrating 60 years as a protector of the Connecticut River.