Mayflies When You're Having Fun
One of our cottage rituals each summer growing up was to head outside after breakfast with a broom to sweep the mayflies off the side of the cottage. There would often be hundreds of them each morning. I thought they were kind of a nuisance (mainly because I was the one doing the sweeping). But my father told me of their importance as a food source to fish. Another common name for these insects is fishflies —although that has more to do with the smell emitted when you get large masses of the dead and decaying carcasses.
Mayfly (Hexagenia ephemeroptera — "Ephemeroptera" means "short-lived").
Mayflies, which are about an inch long, are part of the food web for both fish and many birds. They constitute one of the most important groups of bottom-dwelling animals in streams and rivers throughout the world. They are also found in ponds and lakebed sediments.
They live most of their lives as small nymphs underwater in lake sediments. While the larvae (nymphs) live in water, the adults are delicate flying insects. Adults usually lack a mouth and so are incapable of eating (or biting). They generally live less than three days after emergence. In fact, not only do adult mayflies lack mouths, they have no digestive tracts. Their adult bodies are designed for mating: they truly are love machines.
Mating normally occurs the same day these insects reach adulthood. Females release as many as 8,000 fertile, oval eggs over the water, scattering them or, in some species, laying them in mass in a suitable place. After depositing eggs on the water surface, the flies die, often falling to the water and floating, sometimes drifting onto beaches in nuisance piles. Others are strongly attracted to and congregate under lights at night.
Eggs laid on the water surface gradually sink to the bottom and, after a few days or several months, hatch into tiny aquatic nymphs well adapted for living at the bottom of quiet bodies of water or rapidly flowing streams. Some species burrow into the lake sediment to feed on algae, diatoms, aquatic vegetation, other aquatic insects, etc.The naiads spend four or five years on the lake bottom growing before leaving for their day or two of swarming and mating.
Mayflies are a vital link in the food web of freshwater ecosystems, making energy stored in algae and other aquatic plants available to higher consumers (other invertebrates, fish, birds, etc.). Their healthy population means good water quality.
Some people think of mayfly hatches as a nuisance, and they can be a bit annoying when they are swarming, especially if you are trying to waterski! But mayflies are a good thing. They are rarely found in degraded bodies of water because their external gills in the nymph stage are very vulnerable to silting and pollution. Mayflies are used by scientists as an indicator species when testing for environmental quality, and their presence reflects the good quality of the habitat from which they hatched.
So the next time you are charged with sweeping off the cottage, or are walking along the beach one evening, trying not to ingest mayflies as they swarm the shore, think to yourself: ‘this may be hell, but at least the water quality is good.’
Article by Geoff Peach, Coastal Resources Manager
Caring for Our Coast
To help maintain a high quality shore, the Coastal Centre has produced a new booklet for landowners and shore users called “Caring for Our Coast.” It contains a range of stewardship tips aimed at averting a degraded shoreline and at improving conditions for wildlife species and people.
Some key tips:
- Protect sand dunes. They contribute greatly to the high quality of our beaches. Take care not to damage dune vegetation, and use designated pathways or cross-overs as you make your way to the beach.
- Whatever you bring to the beach, be sure to take back home with you. Litter, especially plastic waste, can be dangerous to wildlife.
- Keep motorized vehicles off beaches and dunes. They can be extremely destructive to these ecosystems, can pollute air and water and can contribute to the spread of invasive plants along the shore.
Canada Day on Lake Huron
Canada Day on Lake Huron is a thing to behold. Fireworks, music, beer tents. And maybe if you’re lucky, the glorious sound of bagpipes!
However you celebrate, it’s a good day to reflect on what a great country we have. And what a great lake we have. You can help us keep it that way by making a donation to support our work in conserving our great lake!
To make a donation click here.