The Canadian Field-Naturalist

The freshwater mussel (Bivalvia: Unionidae) assemblage of the Mississagi River, Ontario: a stronghold for the federally Endangered Hickorynut (Obovaria olivaria)

Kelly A. McNichols-O’Rourke, Mandy P. Gibson, Keith Sayers, Todd J. Morris — Fri, 08 May 2026 00:00:00 +0000

Federally Endangered Hickorynut (Obovaria olivaria) was historically known to occupy a short section of the Mississagi River. Whether this distribution represented the true range of the species or simply reflected a paucity of directed mussel sampling was unclear. The Mississagi River was systematically surveyed in 2023 to evaluate the freshwater mussel assemblage in the watershed, focussing on Hickorynut. The river was divided into 21 contiguous reaches, the first of which was 1 km long, followed by 20, 2 km reaches from the Red Rock Falls Generating Station downstream to the mouth at Lake Huron. Each reach was surveyed at least once using SCUBA; additional surveys were conducted in some reaches if warranted (e.g., historical presence of Hickorynut). In total, 35 sites were surveyed (26 SCUBA, nine snorkel) and 7590 mussels of seven species, including 141 Hickorynut were found. A single Lake Floater (Pyganodon lacustris) was found and genetically verified, representing the third confirmed detection of the species in Canada. Eastern Elliptio (Elliptio complanata) was the most common species found, occurring at all sites. Our results clarify the distribution of mussels throughout this stretch of the Mississagi River and extend the known distribution of Hickorynut ~22 km upstream of its previously known range. These findings will aid in the conservation and management of freshwater mussels in Canada and inform future assessments of atrisk mussel species.

First sighting of Purple-striped Jellyfish (Chrysaora colorata) in Canadian Pacific waters

K.L. Flynn, J.R. King — Fri, 08 May 2026 00:00:00 +0000

We report the first record of a Purple-striped Jellyfish (Chrysaora colorata) from Canadian waters. A single specimen, ~65 cm in bell diameter, was collected in a trawl catch on 4 October 2024 in near-surface waters, off Clayoquot Sound, British Columbia, about 400 km from the previous most northern, research-grade record in the United States. Identification of our specimen was confirmed based on bell texture and size, colouration, number and shape of lappets, and the presence of a quadralinga. In the future, changing oceanographic conditions associated with climate change may lead to C. colorata becoming more common at more northerly latitudes.

The European terrestrial flatworm Microplana cf. terrestris (O.F. Müller, 1773) (Platyhelminthes: Geoplanidae) in a wilderness area of New Brunswick, Canada, suggests a previously unreported pathway to introduction

Donald F. McAlpine — Mon, 11 May 2026 00:00:00 +0000

The terrestrial flatworm Microplana terrestris (O.F. Müller, 1773) (Platyhelminthes: Geoplanidae) is a western European
native that has been introduced to North America and elsewhere. Introduction of terrestrial flatworms outside their native
ranges has been reported to have occurred via the horticultural trade, mainly in contaminated nursery plants and soil. A
second occurrence from Atlantic Canada is documented from a remote wilderness area. Circumstantial evidence suggests
that vermiculture (i.e., the cultivation of earthworms for use as bait in recreational fishing or composting or the use of worm castings as garden fertilizer) may be a previously unrecognized pathway for terrestrial flatworm introduction.