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2017

Marker mayflies

BY RUBY MOORE
Monday, 11 September 2017

Imre captured this incredible swarm on the Danube river with a continuous flashlight and long exposure.

Light fandango Imre Potyó/Wildlife Photographer of the Year

In our Wildlife Photographer of the Year exhibition, one of the most stunning images is of a spectacular swarming mass of mayflies on the Danube River in Hungary. This short-lived nuptial dance occurs at the end of their brief lives. After mating, the female will lay her eggs on the river’s surface, the eggs will hatch into water nymphs that feed on algae, slime and rotting leaves before emerging into a mouthless adult that lives for a few days, just long enough to fly, mate and lay eggs.

Natural Sciences Collection Manager, Ruby Moore, samples a freshwater stream.

Like Potyó, I feel heartened when I see mayflies because their presence indicates that our streams are clean.  Although I haven’t had the opportunity to become cloaked in a swarm of fluttering mayflies like him (our 40 varieties of endemic mayflies don’t swarm en masse), I share his love for this delicate waterborne creature. Indeed, whenever I visit a stream, I love looking under the rocks to find what is living there. From above the water, it may look lifeless, but on closer investigation or by turning over a stone or submerged log, you’ll often find it is humming with life. Pick up a stone and you’ll find snails, worms, midges, caddisflies, damselflies and stoneflies wriggling for cover and under the river-side plants you’ll discover shrimps, crayfish and dragonfly larvae hidden away.

The picture to the left shows poor mayfly habitat, while the picture to the right is an ideal habitat for mayflies. Most mayflies need cool, highly oxygenated water to continually flow past their gills, so they can breathe. High country streams with a steep gradient have lots of well aerated water, and shade-covered streams are good habitat for mayflies. Mayflies also prefer to feed on the thin algae films covering stones and logs in the water found in forested streams rather than the filamentous algae slime mats associated with poorer water quality and streamside vegetation.

Auckland War Memorial Museum Tāmaki Paenga Hira

When looking for these little aquatic creatures, it’s best to look closely because stones or sticks hanging off rocks are often casings with an animal lurking inside. Some types of caddisflies make their houses out of sticks, stones, or sand glued into a case. Under a rock in a clear, clean stream, I am likely to see mayfly larvae scurrying about. They can be easily identified by looking out for their three long tails.

From left to right: a 'flat' mayfly, a 'swimming' mayfly and a 'spiny gilled' mayfly. Mayfly nymphs have six legs, three tail filaments, and gills down the side of their abdomen. They can generally be grouped as “flat”, “swimming”, or “spiny-gilled” mayflies. The flat mayflies have flattened bodies, and strong claws which help them hold onto the beds of fast flowing streams. Swimming mayflies have more streamlined bodies, and a short tail. These are commonly found in the pools of good quality streams. The spiny-gilled mayflies have rigid, upright gills. They are filter feeders, catching bits of organic matter on their leg hairs!

Re-awakening our waterways

Mayfly larvae are the most “sensitive” of our freshwater invertebrates – if their habitat becomes polluted or altered in any way they are the first ones to be snuffed out. For any conservationist, clapping eyes on a mayfly is a golden moment because it indicates stellar stream health. So in recent years, it has been very exciting to work alongside community groups and the Council to bring back our mayflies by improving and monitoring stream quality. Tāmaki Makaurau was once covered in wetlands and streams, however over the years, humans have done their best to drain, de-nude, concrete and pipe these water-ways – effectively leaving these little creatures with little chance of survival. So I have been happy to witness a groundswell of change occurring across Auckland, as community groups take ownership of their local streams and turn little “ditches” into lush-forested, life-filled waterways. People are starting to muck in to re-forest the edges of streams, which provides critical temperature control by producing welcome shade, river-side habitat and a nutritious food supply of fallen leaves.

Project Twin Streams is one such community-driven project that is restoring the habitat for freshwater critters like the mayfly. Since it began in 2003, nearly 800,000 native trees and shrubs have been planted in the Waitakere catchment as part of this project.

In our cities, there has also been a move to “daylight” piped streams. To daylight a stream you essentially bring the stream back to the surface by removing the pipes, restoring the stream banks and landscaping the area to fit with the surrounding area. Then you just wait for the wildlife to turn up! Indeed, one of the most rewarding projects that I have witnessed is the daylighting of the upper reaches of the of Waitahurangi (Avondale) Stream around La Rosa Reserve.  Most people who visited that park would have had no idea that under the grassy slopes there were actually two streams. In 2014, it was daylighted, landscaped and replanted. Now, it is has been turned into a beautiful burbling creek with a winding walkway that offers you stunning views of the steam. I am excited to start seeing the aquatic life come pouring in! Indeed, a particular highlight of mine has been monitoring the Waitahurangi Stream with Avondale College over a number of years, seeing the stream habitat improving and discovering it now is home to mayflies.

The last part of the puzzle in improving mayfly habitat is to reduce pollution. Essentially, all the rain that falls onto our roofs, streets and motorways finds its way into a stream, so it can pick up all sorts of contaminants, from petrol to paint particles and that’s not even taking into account some of the toxins that we unwittingly pour down our storm-water drains. I have sadly been at many streams and witnessed concrete, paint and soap flowing directly into them. Needless to say, streams that become polluted quickly stem populations of invertebrates like midges, caddisflies, damselflies, stoneflies and mayflies are often first to disappear.

In December 2010, the Mayor's office chose Rosa reserve in Green Bay as a flagship daylighting project. In 2014, two tributaries were daylighted from their culverts to return them to their natural state.

Mayflies – like many of our native species – just require the basics, so by unpacking their needs and working to provide them with simple things such as a cool, aerated stream, plentiful food and a toxin-free environment, you’ll be well on your way to welcoming them back. So when you come to pursue the stunning photos at our Wildlife Exhibition of the Year, I hope you take the time to pay a visit to Potyó’s spectacular picture, and also make a date to explore your local stream to go in search of this incredible indicator species! 

  • Post by: Ruby Moore

    Ruby Moore is a freshwater ecologist who has a particular interest in the streams and waterways around the Auckland region.  During her career, she has worked with many school and community groups to raise awareness of the natural environment through education and citizen science. In her current role as Natural Sciences Collection Manager she is working to build a fuller picture of New Zealand’s unique critters and land vertebrates.