**The title, authors, and abstract for this completion report are provided below.  For a copy of the completion report, please contact the GLFC via e-mail or via telephone at 734-662-3209**

 

 

Disruption of alewife recruitment in Lake Michigan by Cercopagis pengoi and Bythotrephes longimanus

Henry A. Vanderploeg ¹

¹GLERL-NOAA

2205 Commonwealth Blvd.

Ann Arbor, MI 48105

 

Radka Pichlová²

²Dept. of Fisheries and Wildlife

Michigan State University

13 Natural Resources Building

East Lansing, MI 48824-1222  

Abstract

Predation of two invasive invertebrate predators, Cercopagispengoi and Bythotrepheslongimanus together with their effects on prey field of YOY fish in Lake Michigan was studied. Additionally, role of adult alewife in controlling competitive and predatory interactions between Bythotrephes and Cercopagis was investigated. We found out that Cercopagis and Bythotrephes predation rate is highly species specific and the predator to prey size ratio plays a role too. They together can consume significant part of prey production in periods of abundance peaks. Size selective predation by adult alewives on Bythotrephes led to removal of Bythotrephes and to dominance of Cercopagis in the nearshore zone; therefore, impacts of these cercopagids are mediated by alewife planktivory. Intensive diel studies at an offshore site showed that Bythotrephes are able to dominate there by remaining high in column above the fish at critical times. The one remaining dominant species of Daphnia in the offshore region avoids both fish and Bythotrephes by undertaking extensive vertical migrations. This study demonstrated that intense diel studies with the latest technologies are necessary to understand the impacts of these and other invasive species.