Seasonal aquatic insect hatches are no different than a garden growing. In the aquatic insect world seeds are planted in the form of eggs. Eggs are deposited shortly after aquatic insects become adults (the hatch) during our summer months.
Living in the rubble on the bottom they slowly mature as nymphs then emerge and become adults around a year later. If the weather keeps the water cooler longer a species of insect may hatch a bit later one year than another. We have seen the first mayfly hatches as early as mid-May and as late as the mid-June.
Aquatic insect cycles are much like your garden. You plant your seeds in the soil, water and wait for them to begin growing. A glance at the package will tell you how many days until a vegetable reaches maturity and is ready to harvest. If the season is colder than normal it will likely take a little longer to mature. If there is lots of sun and rain it may be ready a bit sooner. Do enough gardening over the years and you have a pretty good idea what is going to be ready to pick first and so on throughout the growing season.
For instance radishes are often first to mature, then lettuce, spinach, peas, beans, corn, tomatoes, and brussel sprouts.
In the aquatic insect world there is also an order. Tiny midges are the first to hatch. After midges are the mayfly hatches and on their heals begin the caddis, dragon and damsel flies then the giant stoneflies of summer.
There is no need to get much more complicated than that unless you desire to get scientific about it. As with vegetables there are many varieties of a family of insects. You can find volumes of books dedicated to the mayfly, caddis, or stonefly. It’s fun to be able to identify one species from another but the fish really do not care. The scientific name of particular insect means nothing to fish. It’s simply about size and color.
What was ripe and delicious last week and you could get enough of, say peas , your not even bothering with next week because the green beans are in season an you have moved on to them until the corn comes into season.
Fish feel the same about bugs. There may still be a few Hendricksons still hatching a week after they began, when fish couldn’t get enough of them, but are now passing them by for Red Quills that are just beginning. As hatches progress along fish get sick of the same old thing just like we do and get all excited about the next species to hatch.
So the moral of this story is “What worked for you last week probably isn’t going to work nearly as well next week.” As guides we have a pretty good idea what’s coming next and the best we can hope for is the fly they wanted yesterday still works today, and if it does we know it’s not going to last much longer.
A prime example is the sucker spawn, which is unrelated to insect hatches but a very desired short-term food source. We know suckers are going to spawn sometime around mid-May and the water temperature has to be 48 degrees or above. We start drifting spawn patterns everyday when the conditions are approaching ideal. We know we might be a bit early but we don’t want to miss out. For a day or two nothing pays your best spawn pattern any attention what-so-ever. Then one day you toss it in the same place you’ve fished it the last 3 days and it doesn’t go five feet before something has it. And on that day it seems like every fish in the river wants it. Three days later you’ll fish it all day long and have a hard time convincing three fish they should eat it.
If you don’t have lots of time to follow hatches on your favorite river what can you do to increase your odds of knowing what’s in season? Put a little notebook in your bag. Whenever you have it figured out or hit a particular hatch make a note about it with the date. Odds are the same crop will be ready every year around that same date, give or take a few days.