In a suburban creek steps from busy roads, biologists sent a mild, electrical current into the water and waited to see what surfaced.
The stunned fish they scooped up included spiky mottled sculpins, blacknose dace with striking red racing stripes and chunky creek chub — residents of the largely hidden freshwater world in and around Ontario’s towns and cities.
Scientists are using techniques such as electrofishing and environmental DNA sampling to uncover that biodiversity. They are finding far more species than traditional methods have detected, even as many are disappearing or being replaced by invasive species.
Scientists say protecting creatures from dace and mayfly nymphs to mussels starts with knowing what is there.
But identifying and measuring freshwater life is challenging.
Uncovering little creatures — and bigger ones
A recent study published by University of Guelph biologist Mehrdad Hajibabaei and his team searched for environmental DNA (eDNA) in water from 18 Ontario rivers.
Organisms shed DNA through skin, scales and feces. Using those traces, researchers identified hundreds of aquatic invertebrates that had not been found through traditional methods.
Only 22 species identified through traditional methods were not detected by the DNA survey. Many species were found at just one site, showing how much river life can be missed.
Last year, CBC News accompanied a team using another technique — electrofishing — to count fish in Tannery Creek in Aurora, Ont., near busy streets and subdivisions.
Wearing hip waders, gloves and battery-powered backpacks, Ontario Streams staff dipped pole-mounted rings into the creek, delivering mild electrical shocks that briefly stunned nearby fish. They netted, counted and measured the fish before returning them to the water.
Kat Lucas, then the group’s outreach co-ordinator and spokesperson, said passersby often ask what crews are doing when they see them electrofishing in urban parks around Toronto.
“They’ll be surprised to hear that there are fishes that live in these rivers right through our big cities,” said Lucas, who is now an outreach specialist with Credit Valley Conservation.
Urban creeks are even home to critically endangered species such as redside dace and an Ontario population of Atlantic salmon that went locally extinct a century ago and is now being reintroduced.
A ‘silent mass extinction’
Scientists who compiled data from freshwater surveys around the world reported last year that one-quarter of freshwater animals on Earth are threatened with extinction.
Although half the world’s population lives within three kilometres of freshwater, the researchers noted that “declines are continuing, generally out of sight and out of mind.”
Anthony Ricciardi, a McGill University biology professor who studies freshwater biodiversity, said North America has already lost many species.
“At least 120 extinctions of freshwater animals in North America were recorded over the past 125 years,” he said. “Hundreds of mussels, gastropods, fishes, crayfishes and amphibians are at risk of future extinction.”
Ricciardi calls it a “silent” mass extinction because even conservation biologists “do not seem to be aware or paying much attention to it,” he said.
That’s partly because freshwater biodiversity has traditionally been difficult to measure, as Hajibabaei’s findings show.
‘What’s going on underwater is dramatic’
People who work, play or live beside the water may know little about its inhabitants. That can put species at risk, Ricciardi suggested.
“How would people who don’t know what’s living underwater feel any empathy or any sense of loss?”
As a boy, he waded waist-deep to collect native crayfish and mussels in the St. Lawrence River near Lachine, Que. Many of those species are disappearing, pushed aside by invasive spinycheek crayfish and zebra and quagga mussels.
“Even if the river looks more or less the same,” he said, “what’s going on underwater is dramatic and rapid.”
Freshwater species are going extinct five times faster than animals on land, Ricciardi said. Pollution, invasive species and dams have all taken a toll.
Why we need mussels — and other aquatic creatures
Each species disappearing from rivers and lakes has a job, Ricciardi said, “and as we lose species, some of those jobs don’t get done.”
Native mussels burrow into lake and river beds, helping replenish oxygen needed by other creatures. Insect larvae, including dragonflies, mayflies and caddisflies — groups experiencing “significant” species declines — are essential food for fish.
Hajbabaei said many freshwater species are also important indicators of water quality.
“They are much more sensitive than any other chemical test or physical test,” he said.
Knowing what lives where, and what is disappearing, is “critical” to their conservation, Hajbabaei said.
“You can’t manage something that you cannot measure.”
He said greater public awareness of freshwater neighbours is key. When people know which species live nearby, “they can actually come up with creative ways to protect biodiversity.”
Ricciardi said many declining freshwater creatures could still be saved by reducing polluted runoff, removing dams from rivers and fighting invasive species.
Migratory fish are returning to rivers where dams have been removed, he said, and no new invasive species have been recorded in the Great Lakes since ballast-water regulations were introduced in 2008.
“There are success stories,” he added, “when we intervene to reverse a problem.”
Nearly 800 kidneyshell mussels were released in the Medway Creek in London, Ont. on Wednesday. This is the first time a freshwater mussel species has been reintroduced to a lost habitat in Canada. Find out how these little creatures protect biodiversity.
This is part of a series of articles highlighting the work of scientists looking at disappearing groups of species you may not have thought much about. It’s a chance to get to know them and how they impact our lives, and find out what can be done to keep them around.
