Using environmental DNA metabarcoding to determine endangered Redside Dace occurrence and associated community composition in urban streams

Redside Dace, an endangered fish native to the Greater Toronto Area (GTA),
faces significant threats from urbanization, which has degraded its
habitat and water quality. Understanding its current distribution is
essential for guiding conservation efforts, identifying critical habitats
for protection, and targeting degraded areas for restoration. We collected
water samples from streams previously inhabited by Redside Dace in the GTA
and used eDNA metabarcoding to determine its contemporary distribution and
the associated fish communities. As expected, Redside Dace was less
frequently detected in heavily urbanized streams, highlighting the
negative impact of urbanization. Co-occurrence analysis identified nine
positive associations with other fish species, many of which inhabit cool
water streams and build nests, suggesting possible shared habitat
preferences or reliance on these species as nest hosts. This study
emphasizes the value of eDNA metabarcoding in assessing urbanization’s
effects on Redside Dace and freshwater ecosystems, reinforcing the
importance of focused conservation strategies to protect this endangered
species and restore critical habitats.