Science Advisory Report 2019/012

Recovery Potential Assessment of Redside Dace (Clinostomus elongatus) in Canada

Summary

• Historically, Redside Dace was found in 25 watersheds but has since been extirpated from nine (Pringle Creek, Petticoat Creek, Highland Creek, Mimico Creek, Etobicoke Creek, Clarkson Creek, Morrison Creek, Wedgewood Creek, and Welland Canal) and may be extirpated from 3 more drainages (Don River, Spencer Creek, Irvine Creek). Population status is poor for 9 other watersheds (Lynde Creek, Duffins Creek, Rouge River, Credit River, Sixteen Mile Creek, Bronte Creek, Holland River, Gully Creek, Saugeen River).
• The species prefers cool, clear streams and adults are found in pool and riffle habitats over a variety of substrates but most commonly gravel. Important habitat features include overhanging riparian vegetation (grasses, forbs, and shrubs), meander belt, and in-stream structures such as boulders and woody debris.
• To achieve 99% probability of persistence, given a 15% chance of catastrophic decline (50% reduction in abundance) per generation, the minimum viable population (MVP) ranged from ~18,000 adults to ~75,000 adults depending on the meta-population structure that exists as well as the MVP simulation criteria. The minimum area required to support an MVP population size (MAPV) ranged from ~3.2 ha for a population with 4 sub-populations affected by catastrophes independently to ~13 ha for a population where the entire population was impacted by catastrophes simultaneously.  
• The greatest threats to the survival and persistence of Redside Dace in Canada are residential/commercial development, intensive agricultural practices, pollution, natural systems modification, and introduced species (i.e., Brown Trout [Salmo trutta], Rainbow Trout [Oncorhynchus mykiss]). Lesser threats that may be affecting the survival of the species include human intrusion and biological resource use such as bait harvesting.
• The dynamics of Redside Dace populations are particularly sensitive to perturbations that affect survival of immature individuals (from hatch to age-2) and population-level fecundity. Harm to these portions of the life cycle should be minimized to avoid jeopardizing the survival and future recovery of Canadian populations.
• Sources of uncertainty include knowledge gaps in distribution, abundance, biology, and threats. Further research is required to address the key factors associated with urban development and agriculture that cause declines, the impacts of introduced species, and climate change effects.

This Science Advisory Report is from the February 21-22, 2018 Recovery Potential Assessment for Redside Dace (Clinostomus elongatus) in Canada. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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