Gravel chub (Erimystax x-punctatus) COSEWIC assessment and status report: chapter 2

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Executive Summary

Species information

The gravel chub is a slender, round-bodied minnow with an average length of 76 mm TL (Total Length) and a maximum length of approximately 100 mm TL. It is the only member of the genus Erimystax known to have existed in Canada.

Distribution

The gravel chub is widely distributed in east-central North America. In Canada, the species was only known to occur in southwestern Ontario in the Thames River.

Habitat

In North America, the species was only known to occur in clear to moderately turbid streams with permanent flow. The streams typically have well-defined sand, gravel or rocky riffles, and their currents keep the bottom free of unconsolidated silts and clays. The species tends to avoid areas with macrophytes, larger algae species and aquatic moss species. In Ontario, the species once inhabited sections of the Thames River. These river sections have constant flow and are 1-3 m deep; the bottom is composed of sand, rock and stone with areas of soft organics and silt. The water is turbid here, and there is very little vegetation along the riverbanks.

Biology

Little is known about the gravel chub’s general biology. Adult specimens from Canada were 52-57 mm in length and spawning occurs in Kansas sites in early spring. The main food is probably insects attached to the bottom. The gravel chub is also thought to probe under rocks and into crevices with its sensitive snout.

Population sizes and trends

The gravel chub has been reported at only two Canadian sites, but has not been found at these, or other suitable sites in Canada, since 1958.

Limiting factors and threats

The gravel chub has specific habitat needs. It is only found in waters of low turbidity with enough current to keep the bottom silt-free. These conditions limit the species’ occurrence. In addition, impoundment of riffle areas is a threat to the gravel chub. It is thought that increased turbidity and siltation may have led to the extirpation of the gravel chub.

Special significance of the species

The Ontario populations were the only representation of the genus Erimystax in Canada and the only evidence for the existence of this species in waters of the Great Lakes basin. The greatest importance of this species to man may be as an indicator of habitat degradation due to its sensitivity to siltation.

Existing protection or other status designations

The gravel chub is listed as an Extirpated species under the federal Species at Risk Act (SARA). Besides offering legal protection to the species and its habitat, the Act requires the development of recovery strategies.

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 5, 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 (2008)

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)^Footnotea

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)^Footnoteb

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)^Footnotec

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.