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First finding of the amphipod Echinogammarus ischnus and the mussel Dreissena bugensis in Lake Michigan

Journal of Great Lakes Research

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Abstract

The first finding of the amphipod Echinogammarus ischnus and the mussel Dreissena bugensis in Lake Michigan is documented. These two species are widespread and abundant in the lower lakes, but had not yet been reported from Lake Michigan. E. ischnus is generally considered a warm-water form that is typically associated wtih hard substrates and Dreissena clusters in the nearshore zone. Along the eastern shoreline of Lake Michigan, this species was present at rocky, breakwall habitats, along the entire north-south axis of the lake. Although not abundant, this species was also found at soft-bottom sites as deep as 94 m in the southern basin. The finding of this species in deep offshore waters apparently extends the known habitat range for this species in the Great Lakes, but it is found in deep water areas within its native range (Caspian Sea). D. bugensis was not abundant, but was present in both the southern and northern portions of the lake. Individuals of up to 36 mm in length were collected, indicating that it had probably been present in the lake for 2 or more years. Also presented are depth-defined densities of D. polymorpha at 37 sites in the Straits of Mackinac in 1997, and densities at up to 55 sites in the southern basin in 1992/93 and 1998/99. Mean densities decreased with increased water depth in both regions. Maximum mean density in the Straits in 1997 was 13,700/mA? (a?? 10 m), and maximum density in the southern basin in 1999 was 2,100/mA? (a?? 30 m). Mean densities at the a?? 30-m interval in the southern basin remained relatively unchanged between 1993 and 1999, but increased from 25/mA? to 1,100/mA? at the 31 to 50 m interval over the same time period. D. polymorpha was rare at sites > 50 m. The presence of E. ischnus and the expected population expansion of D. bugensis will likely contribute to further foodweb changes in the lake.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
First finding of the amphipod Echinogammarus ischnus and the mussel Dreissena bugensis in Lake Michigan
Series title:
Journal of Great Lakes Research
Volume
27
Issue:
3
Year Published:
2001
Language:
English
Contributing office(s):
Great Lakes Science Center
Description:
p. 384-391
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Great Lakes Research
First page:
384
Last page:
391