May 6, 2013


Slimy and deepwater sculpin: adaptability in underappreciated native Great Lakes fishes

Ann Arbor, MI — Despite recent and unprecedented declines in their favorite invertebrate prey, Lake Michigan slimy and deepwater sculpin are not starving.

Over the last decade and a half, populations of this prey, called "Diporeia," crashed in Lake Michigan. Fishery managers feared that without this key prey, slimy and deepwater sculpin would have less to eat and their health could suffer. In addition, their role as important invertebrate predators and prey for native fishes could be affected.

Although they are relatively abundant in some lakes compared to other fishes and even recent invaders like round goby, little is known about the biology of these sculpin species. In particular, estimates of daily consumption (or how much a fish eats in a day) do not exist for these species.

"Slimy and deepwater sculpin occupy an important role in the Great Lakes food web because they eat invertebrates and fish eggs and are themselves eaten by predators such as lake trout. Because of this role, any negative impacts on sculpin populations have the potential to adversely impact the entire foodweb," says Justin Mychek-Londer, a scientific contractor at the USGS Great Lakes Science Center. "Accurate estimates of consumption by sculpins will help address concerns such as whether they’re eating less today than in the past and what the potential effects of their predation on native fish eggs may be."

Our work provides the first daily ration model for slimy and deepwater sculpin and reveals that as Diporeia have declined, each sculpin species supplemented its diet by eating more of other prey. An unexpected result was that both species appeared to be eating as much, if not more today (as percent bodyweight) than in the past when decreases in Diporeia had yet to occur. As each sculpin species found different prey types to eat in the absence of Diporeia, results suggest they can co-exist where spatial overlap occurs despite a lack of important prey.

Additional methods in this research will allow for first-time estimations of exactly how many fish eggs or how many other prey sculpin consume, adding to the ability to better manage Great Lakes fisheries and increasing the knowledge of roles sculpins play in the foodweb. Results support that slimy and deepwater sculpin restoration and recovery efforts could work in Lake Ontario where presently deepwater sculpin exist marginally or are extirpated, slimy sculpin populations are reduced, and Diporeia have been extirpated as a result of recent and similar environmental changes as Lake Michigan has experienced.

Original Publication Information

Results of this study, "Gastric evacuation rate, index of fullness, and daily ration of Lake Michigan slimy (Cottus cognatus) and deepwater sculpin (Myoxocephalus thompsonii)," are reported by by Justin Mychek-Londer and David (Bo) Bunnell in Volume 39, No. 2, of the Journal of Great Lakes Research, published by Elsevier, 2013.


For more information about the study, contact David (Bo) Bunnell: USGS Great Lakes Science Center, 1451 Green rd. Ann Arbor, MI 48105;; (734) 994-3331 extension 278.

For information about the Journal of Great Lakes Research, contact Stephanie Guildford, Scientific Co-Editor, Large Lakes Observatory, University Minnesota Duluth, 2205 East Fifth Street, Duluth, Minnesota, 55812-2401;; (218) 726-8064.

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.