The annual swarms of shad flies are back in North Bay

The swarms of shad flies are making their annual appearance in North Bay, but not nearly in the numbers one retired biologist remembers.

"You would have so many shad flies you would have to shovel them off your porch like you would shovel snow," recalled Jean-Marc Filion

"I haven't seen that for many decades now. So, for one reason or another, the population of shad flies in Lake Nipissing has gone down," he said.

Filion said this year they hatched a little later, because of the cool spring.

He's not sure what has caused the drop in the numbers, but climate change may be one of the reasons.

"Either something's eating the eggs, or the eggs are being deposited in water that is too warm or too cold. It's just not exactly clear at this point in time what is going on. But, for sure, when I was a kid there was way more of these shad flies." Filion said.

The role of adultshad flies, also called mayflies,is just to mate and lay eggs before they die, according to Bruce Doran, writing on the Science North website.

"In fact, adult mayflies do not have mouthparts and die several days after they have emerged. Hence, we do not have to be afraid of them since they cannot bite," Doran wrote.