Invasive mussels seen as threat in Sydenham River
Zebra and quagga species pushing out native species: conservation biologist
No other river has more species of freshwater mussels and it has several species that are either not found anywhere else.
The Sydenham River is considered one of the richest and most bio-diverse rivers in North America. The 165-kilometre waterway winds its way from just west of London, through Lambton County and into Dresden and Wallaceburg before emptying into Lake St. Clair.
With 35 species of freshwater mussels, several of which can’t be found anywhere else, the Sydenham is an incredible treasure that needs to be protected against the twin dangers of habitat loss and invasive species, said Erin Carroll, biology manager for the St. Clair Region Conservation Authority.
During a presentation to Lambton Wildlife Inc., Carroll outlined the history and biodiversity of the Sydenham, originally known by local First Nations as Jonquakamik or Milky River because of its murky colour.
“The Sydenham is one of the most mussel-diverse rivers in all of Canada,” she said. “No other river has more species of freshwater mussels and it has several species that are either not found anywhere else or can only be found in a couple of other spots globally.”
Along with being home to 35 freshwater mussel species — such as the Lilliput mussel, the purple wartyback mussel and the snuffbox mussel, all of which have developed creative ways of releasing their fertilized eggs into host species — the river is also home to 82 species of fish, which include at-risk species such as the eastern sand darter and the blackstripe topminnow.
The Sydenham is also a habitat for the endangered eastern spiny softshell turtle, whose numbers have slightly recovered in part due to efforts by the conservation authority, Carroll said.
“We’ve worked hard to try and recover that species,” she said. “It started out with canoe surveys to find out where they were and then building on that, understanding where they’re nesting.
“In the last year, we were actually able, in some situations, to incubate eggs that were at immediate risk of being lost, and we were able to release little turtle hatchlings back into the river. It was very successful, we had about 400 turtles released back into the river.”
Yet it’s the river’s wide range of freshwater mussels, mollusks that can reach up to 20 centimetres in length and can live for decades on end, that are of great significance, Carroll said, because they serve as a type of early warning indicator for the river’s overall health.
“Freshwater muscles are an indicator species,” she said. “They are sensitive to many kinds of pollution and habitat alteration ... and because they are longlived and accumulate many toxic substances, they can be used as bio-indicators of environmental contamination.”
She said it’s important to protect these freshwater mussels.
“People should care because if they have a general interest in biodiversity and an interest in maintaining what we have, these (mussels) are like canaries in the coal mine for what’s going on, on a larger scale,” Carroll said.
Unfortunately, two factors challenging the survival of the Sydenham’s unique species of freshwater mussels are the mussels’ loss of habitat as well as the introduction of the zebra and the quagga mussels, two invasive species inadvertently brought from the Caspian Sea to the Great Lakes in ballast water aboard an oceangoing ship during the mid-1980s.
“They’ve multiplied rapidly and now out-compete the (native freshwater mussels) in their habitat and have absolutely decimated the Great Lakes populations,” Carroll said. “They’re only in the lower reaches of the Sydenham River at this point.”
While habitat loss and degradation have been a big problem in the past, members of the public are now co-operating with the conservation authority to reduce the amount of habitat loss, Carroll said.
“We’ve worked with other partners to create a Sydenham River Recovery Strategy and a subsequent action plan,” she said. “These documents take a larger view, looking at all the species present in the river, with a particular emphasis on the species at risk and what can be done to help recover these animals.
“I think most people really care, so if they have marginal land along the riverbank that they can retire, they tend to do that. If they can plant trees, create wetlands, even if they want to download the ‘Clam Counter app’ (a smart phone app developed by the Toronto Zoo and Fisheries and Oceans Canada) where they can report mussel sightings and that information is shared amongst many organizations, then they do that too,” Carroll continued.
“Every little bit helps and I’ve found that the majority of our landowners are keen on protecting our river.”