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ICAIS Media Advisory

Media Advisory for ICAIS 2019.pdf 

Media Contact: Deb Sparks, Invasive Species Centre, (705) 255-8301, dsparks@invasivespeciescentre.ca




The Tench, a European species of bottom-dwelling fish, is likely to be the next invasive species to colonize the Great Lakes – the world’s largest and most invaded freshwater ecosystem. In the late 1980s, about 30 live fish were imported from Germany by a Quebec farmer who reared them in ponds on his property in the Richelieu River. Fish from these ponds escaped into the Richelieu River in 1991 when the ponds were drained by the farmer, who had abandoned his project after it became apparent there was no commercial demand for the species. By 2000, the fish was discovered to be reproducing in the river. By 2006 it appeared in the St Lawrence River at Lac Saint Pierre. Since 2006, the population grew exponentially in the St. Lawrence River and had spread like a travelling wave upstream to Montreal and downstream to Quebec City. In the autumn of 2018, a single specimen was collected in the Bay of Quinte, Lake Ontario. A recent assessment * of the ecology of the species determined that the Great Lakes are highly vulnerable to a Tench invasion. A review of published research indicates that the species can compete with other bottom-dwelling fishes, transmit parasites and diseases to other fishes, degrade water clarity in shallow lakes and wetlands, constrains submerged plant growth, reduces invertebrate populations which serve a s food for other fishes, and promotes bottom algal growth. It is considered to be a potential threat to the endangered copper redhorse (chevalier cuivré) – Quebec’s only native vertebrate species. Tench can tolerate temperatures from 0 to 38C, which gives it an advantage over many native species under a rapidly warming climate. ICAIS will feature three talks and two research poster presentations on the ecology, invasion success and impacts of Tench. *Avlijas, S., A. Ricciardi, and N.E. Mandrak. 2018. Eurasian Tench (Tinca tinca): the next Great Lakes invader. Canadian Journal of Fisheries and Aquatic Sciences 75: 169-179.


The impacts of invasive species can vary greatly over space and time as they are affected by local environmental conditions. In other words, impacts are ‘context dependent’, and this poses a major challenge for forecasting when and where an introduced species will cause the greatest impacts. An emerging experimental method has been developed by researchers from Queen’s University Belfast. Many ecological impacts are related to how well an introduced species consumes resources. The new methodological approach tests the ‘functional response’ of the species (how efficiently it consumes food, for example) under different contexts and compares these responses to ecologically similar native species. This method has accurately distinguished between high-impact invasive and low-impact species and has thus proven to be a very promising risk assessment tool for prioritizing invasion threats. McGill researchers have adapted this method to forecasting how climate change will affect the success and impact of invasive species. Previous risk assessments in the Great Lakes and most other aquatic ecosystems have not considered how currently established invasive species and future invasion threats are influenced by climate change. Researchers at McGill have applied the comparative functional response method on invasive fishes and crayfishes in water temperatures projected under different warming scenarios for the Great Lakes, to determine who will be the ‘winners’ and ‘losers’ under climate change in the next two decades. Several scientists at ICAIS will be presenting research on the functional response method.


After more than 25 years since the zebra mussel had begun to invade Quebec waterways (beginning with the St Lawrence River in 1991), the mussel was discovered in Lac Memphremagog. In 2017, a single specimen was found near Magog. In the summer of 2018, an established population was observed – including some mussels that were large enough to be at least two years in age, suggesting that the invasion began in 2016. In 2019, Divers confirmed that the zebra mussuel population was expanding but was still at low abundance, with recorded zebra mussel densities of less than 15 individuals per square meter. What remains to be seen is to what extent and how fast the population will grow. Lac Memphremagog’s water chemistry is deemed to be sufficient but suboptimal for zebra mussel persistence. The species thrives in highly alkaline waters, such as those found in Lac Massawippi. There is a risk that the mussel will be transported (e.g. attached to boat trailers) by recreational water users to neighboring waterways including Lac Massawippi. Thus, although the zebra mussel has been present in Quebec for three decades, it continues to invade waterways including those that are considered suboptimal environments for the species. Meanwhile in the St Lawrence River, the zebra mussel is fighting a turf war with another invasive species, a close relative called the quagga mussel, which has become dominant in most areas of the river.