Paddlefish (Polyodon spathula) COSEWIC assessment and status report: chapter 2

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Executive Summary

Species information

The paddlefish (Polyodon spathula) is an ancient species and, like its close relatives the sturgeons, it has been fished for its eggs, which are processed into caviar. It is a thick, robust fish with a long, spatula-like snout and a large, toothless mouth. The skin is smooth and scaleless.

Distribution

The present range of the Paddlefish is the Mississippi River system from Montana to Louisiana, and some smaller rivers draining into the Gulf of Mexico. In Canada, paddlefish were last reported about 90 years ago when they were occasionally encountered in lakes Huron, Superior, and Erie.

Habitat

There is little or no information on paddlefish habitat preferences in Canada. Paddlefish specimens collected from Canada at the turn of the 20^th century were taken from inshore areas, or from moderately large tributary rivers of the Great Lakes.

Biology

There is no information on the general biology of the populations of paddlefish that inhabited the Great Lakes; the information available is from the populations of the Mississippi River system. Paddlefish can live for up to 50 years, or more, and reach lengths of up to 2 m, and weights in excess of 80 kg. Males reach sexual maturity at about 7-10 years of age, while females reach sexual maturity between the ages of 14 - 17. Females spawn every 2 to 7 years. Paddlefish migrate over long distances, preferring reservoirs or lakes during the winter and large rivers during the spawning season.

Population sizes and trends

The paddlefish was known from Canada from specimens collected in Lake Huron, near Sarnia; in the Spanish River, tributary to Georgian Bay; and in Lake Helen on the Nipigon River. The species was also known from Lake Erie based on collections in the American waters of the lake. Since the turn of the 20^th century, the peripheral range of the paddlefish began to shrink and the relict population of the Great Lakes has been lost. None have been collected in Canadian waters for over 90 years.

Limiting factors and threats

There are five main limiting factors that affect paddlefish populations: the degradation or destruction of areas used for spawning; the construction of dams which block the movements of this species; a reduction of the amount of water in streams; industrial pollution; and, because this fish matures so slowly, over-harvesting, which can quickly deplete a population.

Special significance of the species

In areas where paddlefish are extant this species is recognized as a sport and commercial species (primarily for caviar). Significant public and scientific interest has been generated in the species since it represents one of the most primitive groups of fishes in North America, and is of interest to the scientific community for genetic and evolutionary studies.

Existing protection or other status designations

The paddlefish was assessed by COSEWIC in April 1987 as Extirpated, and this status was reconfirmed in May 2000. It is currently listed as an Extirpated species under Schedule 1 of the federal Species at Risk Act (SARA) [EC 2007]. Besides offering legal protection to the species and its habitat, the Act requires implementation of recovery initiatives.

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.