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COSEWIC Assessment and Update Status Report on the Redside Dace in Canada

Technical Summary

Clinostomus elongatus

redside dace
méné long

Range of Occurrence in Canada: southern Ontario


Extent and Area Information

Extent of occurrence (EO)(km2) Calculated using polygons in ArcView 3.2 that encompass the global and Canadian distributions as defined by COSEWIC (see Fig. 2)
Global: 930 000
Canada: 46 900





Specify trend in EO

decline

Are there extreme fluctuations in EO?

No

Area of occupancy (AO) (km2)

≈ 4 km2 (based on occupied stream length X steam width as determined from 1:50 000 topographic maps)

441 km2 (based on overlaid grid of cell size one km2, total AO is the number of occupied squares that are intersected by streams)

Specify trend in AO

decline

Are there extreme fluctuations in AO?

No

Number of known or inferred current locations
(watersheds see Table 1)

14 -19



Specify trend in # of locations - extirpated from 6 and possibly extirpated from another 4

decline



Are there extreme fluctuations in number of locations?

No


Specify trend in area, extent or quality of habitat

decline


Population Information

Generation time (average age of parents in the population)
3 years


Number of mature individuals

Unknown

Total population trend:

decline

% decline over the last/next 10 years or 3 generations.

unknown


Are there extreme fluctuations in number of mature individuals?

unlikely


Is the total population severely fragmented?

yes


Specify trend in number of populations

decline

Are there extreme fluctuations in number of populations?

No

List populations with number of mature individuals in each: see Table 1- number of individuals unknown in all populations


Threats (actual or imminent threats to populations or habitats)

  • Urban development and its associated impacts (instream channel structure changes through peak flow increases and channelization, increases in siltation, removal of riparian vegetation, increases in water temperatures, reductions in groundwater inputs, increases in contaminants)
  • Introduced species (competitors and predators such as trout, bass, and pike)
  • Intensive agriculture and its associated impacts (removal of riparian vegetation, increases in siltation, channelization, pesticides, manure spills)
  • Water extraction (reduced flows, increased stream temperatures)
  • Stream barriers
  • Succession from field to dense forest (reductions in suitable riparian vegetation)
  • Climate change (potential for reducing stream flows or increasing flooding events)
  • Bait harvesting
  • Scientific collecting


Rescue Effect (immigration from an outside source)

Status of outside population(s)?
USA: Secure (N4)
[other jurisdictions or agencies]

Is immigration known or possible?

No

Would immigrants be adapted to survive in Canada?

Yes


Is there sufficient habitat for immigrants in Canada?

Unknown


Is rescue from outside populations likely?

No


Quantitative Analysis

Not Applicable


Current Status

National and Sub-national Heritage Ranks – see Table 2
Wild Species 2005 – National - 1, ON –1 (At risk) [Canadian Endangered Species Council 2006]

Ontario (COSSARO:
Threatened)

COSEWIC:
Special Concern 1987
Endangered 2007


Status and Reasons for Designation

Status: Endangered
Alpha-numeric code: B2ab(I,ii,iii,iv,v)

Reasons for Designation: This species is especially sensitive to stream alterations that interfere with flow regimes and lead to increased siltation and water temperatures. It has been lost from 5 of its 24 historic locations, and may now be gone from an additional 5; continuing decline is evident in 8 of the 14 remaining locations. More than 80% of the Canadian distribution occurs in the ‘Golden Horseshoe Region’ of southwestern Ontario where urban development poses the most immediate threat to the continued existence of this species in Canada. The 6 stable populations are on the fringe of urban development in watersheds that are, as yet, relatively undisturbed, but more than 50% of these locations are in, or adjacent to, areas that are expected to be developed within the next 10 to 15 years.


Applicability of Criteria

Criterion A (Declining Total Population):
Not Applicable – decline rate unknown

Criterion B (Small Distribution, and Decline or Fluctuation):
Meets criterion B2 as the area of occupancy is well below the threshold value. Criteria B2a, and B2b(i,ii,iii,iv,v) are also met as populations are fragmented, and continuing decline is observed in the extent of occurrence and occupancy, as well as the extent and quality of habitat, number of locations and number of mature individuals.

Criterion C (Small Total Population Size and Decline):
Not applicable – the number of mature individuals is unknown.

Criterion D (Very Small Population or Restricted Distribution):
Not Applicable – distribution and number of locations exceed threshold values.

Criterion E (Quantitative Analysis):
Not Applicable – no data available for quantitative analysis.