Spotted sucker (Minytrema melanops) COSEWIC assessment and status report: chapter 7

Population Sizes and Trends

No studies examining population size or trends have been conducted on Canadian populations. Between 1962 and 1992, 24+ spotted sucker were collected from Canadian waters. Since 1992, 67+ specimens have been collected. Fifty - four of the 67+ spotted sucker collected since 1992 were collected in 2002 and 2003. Almost all specimens collected have been adults. While spotted suckers haves been collected from new sites since the last update status report, its regional distribution in southwestern Ontario is unchanged as the recent records mentioned in the following paragraph are within the Canadian range previously described for this species. There have, however, been significant changes in the distribution within this area, as indicated by the large number of post-1990 records.

The comparatively large number of individuals captured in the past 2 years is considered to be the result of increased sampling effort and the use of boat and backpack electro-fishing gear. The use of electro-fishing gear has resulted in improved distributional information for other rare catostomid species (M. carinatum and M. valenciennesi) in the Ohio (Yoder and Beaumier 1986) and Illinois rivers (Retzer and Kowalik 2002). The low number of spotted sucker records identified in previous status reports might also reflect a lack of interest by resource managers or proper species identification. For example, historical commercial fisheries records of all catostomids in Lake Erie and Lake St. Clair were simply reported as “suckers” (Baldwin et al. 2000).

The distribution of thespotted suckerin the Detroit River, St. Clair River, Sydenham River and Thames River drainages has expanded since 1990. In June of 1996, a single specimen was collected with a seine net from Maxwell Creek (Lake St. Clair drainage) which represents a new occurrence for the spotted sucker. In 1997, a single juvenile was captured from Bear Creek, North Sydenham River drainage (Dextrase and Holm, 2001). Although specimens have been collected from North Sydenham tributaries in the 1980s, this is the first spotted sucker record from the Bear Creek portion of the drainage. In 2002 and 2003, 27 spotted sucker were collected from 14 sites throughout the Sydenham River and nine from six sites along the Detroit River. In 2002, nine spotted sucker were collected from two other locations along the Canard River. In 2003, spotted suckerwere caught at three sites in the Thames River drainage as far as 75 km upstream of historical records. Spotted suckerwere alsocaught for the first time in Whitebread Drain, a tributary of the St. Clair River, in 2003.

A single spotted sucker was captured in a gill-net during the fall of 2000 from west-central Lake Erie (OMNR 2001). It was the only record from over 187 000 fish sampled during an 11 year monitoring period (1990-2001). There have been no recent records of spotted sucker from Lake St.Clair (last record 1984).

The potential rescue effect of neighboring United States populations is interpreted to be moderate. While nearby source populations exist in western Lake Erie and the Huron-Erie corridor, it is not a common species. The status of spotted sucker in adjacent Michigan is vulnerable (S3) and imperiled in Pennsylvania (S2) (NatureServe 2004). In Ohio, its status has not been ranked. Its abundance in Lake Erieand its tributaries is considered to be a fraction of historical abundance (Trautman 1981).

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