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Recovery Strategy for Paddlefish (Polyodon spathula) in Canada (Proposed)


Executive Summary

In Canada, the past occurrence of paddlefish (Polyodon spathula) is known from only four individuals collected from the Great Lakes basin, the most recent in 1917. Currently, paddlefish is considered extirpated from the Great Lakes basin. Disagreement exists as to whether these Great Lakes paddlefish records represent an historic resident population or were vagrants from the Ohio River and/or Mississippi River.

Paddlefish was designed as Extirpated by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 1987. This status was re-examined in 2000 by applying new quantitative criteria to the information contained in the 1987 status report, and the status of Extirpated was confirmed.

The paddlefish is a large, primitive fish with a typical specimen having an average length of 0.5-1.2 m and weighing 0.9-9 kg. Larger individuals can attain lengths of 2 m and weights of more than 80 kg. The paddlefish has a long, paddle-shaped snout which is approximately 1/3 the length of the fish, and a very long, pointed, opercular flap that nearly reaches the pelvic fin. It has no scales aside from a few rhomboid scales on the tail. Colouring is gray to blue-black dorsally and laterally and whitish ventrally.

In the United States, adult paddlefish inhabit the slow waters of medium to large rivers, channels, oxbows, impoundments, backwaters and river-margin lakes. Paddlefish are primarily zooplanktivorous, but occasionally consume small insects, insect larvae and small fishes.

Population growth is limited by late sexual maturity and intermittent spawning by females. Paddlefish require a long period of time to become sexually mature, which is estimated at 7 years for males and 9-10, possibly up to 12, years for females. While male fish are able to spawn each year, several studies suggest that females require 2 to 5 years to develop mature ova between spawning bouts.

In the spring, spawning is generally preceded by an upstream migration (sometimes over extremely long distances) to the spawning area. Successful migration to spawning habitats and initiation of spawning is dependent on barrier-free migration routes and specific water temperatures and flow levels. Paddlefish recruitment is therefore vulnerable to natural and man-made changes to these factors.

It has been determined that recovery of the paddlefish in Canada is not feasible as only four individuals have ever been found in Canada. There is no evidence that there were ever any reproducing populations in Canada, and it is likely the four individuals collected in Canada in the late 1800's and early 1900's represent vagrants from the United States.