Speckled dace (Rhinichthys osculus) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

Speckled dace
Rhinichthys osculus

Species information

The speckled dace (Rhinichthys osculus) is a small minnow (usually less than 70 mm in total length) with a robust elongate body. It is grey to brownish grey in colour with dark flecks. Speckled dace in Canada are isolated above a 30.5-m high barrier at Cascade Falls, Columbia drainage, British Columbia. The absence of barbels and high scale counts around the caudal peduncle differentiate them from populations in the United States below the barrier. Many subspecies and distinct populations are recognized in the United States, and many of these isolated populations are considered to be at risk.

Distribution

Speckled dace are only found in western portions of the United States and Canada. In the United States, populations occur as far south as California, Arizona and New Mexico. In Canada, they reach the northern limit of their distribution and are confined to the Kettle River system (Kettle, West Kettle, and Granby rivers) of south central British Columbia (BC).

Habitat

In Canada, speckled dace are found among the larger bottom substrates of riffle habitats where they can hide from predators and feed on aquatic insects. They have been captured at depths of over 1 m. Small young-of-the-year fish are often reported from shallow stream edge habitat. In the Kettle River system, extreme low flows occur during the winter months while low summer flows occur during August and September. Peak flows occur in the April to June period with snowmelt conditions.

Biology

Existing data indicate that they breed in July at sizes larger than 40 mm standard length, probably spawning for the first time at the age of 2+ or 3+. Speckled dace are not likely to live beyond the age of four. Depending on their size, mature females can carry between 400 and 2,000 eggs. Newly hatched fry can be seen in August and September.

Population sizes and trends

No quantitative sampling throughout the Kettle River system has been completed in Canada. Numbers may be declining based on inferred trends in the amount of limiting habitat.

Limiting factors and threats

Limited range within a single river system and lack of abundance are major risk factors for speckled dace in Canada, where they are isolated above a natural barrier from other populations.  A single natural or man-made event could be disastrous for a significant portion of the total population. Abundance appears to be limited by the availability of good quality habitat for adults, which is presumed to be decreasing partly as a consequence of low summer flows.

Special significance of the species

The range of the species in Canada consists of only a few (probably less than 10) populations that represent the most northern extent of the species range. Speckled dace above the barrier at Cascade differ morphologically from other populations in the United States as they lack barbels and have much higher scale counts.

Existing protection

Speckled dace in Canada receive general protection under federal legislation, the federal Fisheries Act, and provisions of various provincial statutes designed to protect the environment, water quality and fish. None of this legislation specifically protects speckled dace or its habitat.

COSEWIC History

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list.  On June 5th 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species. 

Definitions (2006)

Wildlife Species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)
A wildlife species that no longer exists.

Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A wildlife species facing imminent extirpation or extinction.

Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)**
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)***
A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
** Formerly described as “Not In Any Category”, or “No Designation Required.”
*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

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