Bloaters produce 24% fewer eggs today
Ann Arbor, MI — Bloater, one of Lake Michigan's native prey fish, has been declining in abundance since 1989 and scientists have been unable to explain this disturbing pattern.
Researchers recently compared how many eggs an individual bloater in Lake Michigan produced in 2006 to the number that was produced in 1969, when the ecosystem was less disturbed and when Diporeia, an important invertebrate bloater prey, was still abundant. They found that bloater were 24% less fecund in 2006 than in 1969, and attributed the decline to the disappearance of Diporeia.
"The decline of bloater is troubling because it is a native species that has historically filled an important niche in the Lake Michigan food web. In addition, bloaters (or "chub") support a commercial fishery that has been negatively affected by its declining population," says David "Bo" Bunnell, Research Fish Biologist at the USGS Great Lakes Science Center.
Bunnell and colleagues concluded, however, that limited egg production was not the sole factor underlying the bloater decline.
"Lower fecundity likely has contributed to the downward trend in bloater numbers, but we do not think it is the primary reason."
In fact, they have embarked upon a new research study that evaluates whether slimy sculpin and round goby consumption of bloater eggs may be a more critical factor.
Original Publication Information
Results of this study, "Decline in bloater fecundity in Southern Lake Michigan after decline of Diporeia," are reported by David Bunnell, Solomon David, and Charles Madenjian in the latest issue (Volume 35, No. 1, pp. 45-49) of the Journal of Great Lakes Research, published by Elsevier, 2009.
Contacts
For more information about the study, contact Bo Bunnell, USGS Great Lakes Science Center, Ann Arbor, MI 48105, dbunnell@usgs.gov, (734) 214-9324.
For information about the Journal of Great Lakes Research, contact Marlene Evans, Editor, National Water Research Institute, 11 Innovation Boulevard, Saskatoon, SK, S7N 3H5, Canada; editor@iaglr.org; (608) 692-1076.
Since 1967, IAGLR has served as the focal point for compiling and disseminating multidisciplinary knowledge on North America's Laurentian Great Lakes and other large lakes of the world and their watersheds. In part, IAGLR communicates this knowledge through publication of the Journal of Great Lakes Research, available to members in print and electronic form. A searchable archive of the journal is available online and includes the abstracts of articles from the journal's inception in 1975 through the most recent issue. In addition, complete articles are available to members who have signed up for an electronic subscription.