Help Manage our Muskellunge

Background on the Cleithrum Project

In the late 1970's, a concern arose amongst fisheries biologists that valuable biological information was being lost as large, trophy muskellunge (Esox masquinongy) were "fished up". This information is important for managers of muskellunge fisheries in assessing the status of populations and subsequently regulating them. However, fisheries workers using conventional 
sampling techniques rarely see muskellunge and the relatively small population sizes do not allow for intensive sampling. As a group, anglers and taxidermists handle more muskellunge than fisheries professionals. 

photo by John M Casselman

Thus, in 1979, the Ontario Ministry of Natural Resources, through Dr. John Casselman, and the Royal Ontario Museum, through Dr. Ed Crossman, initiated the Cleithrum Project as a joint study to collect, archive, and disseminate biological data on trophy muskellunge.

A guiding principle of the project is fish should not be killed for the data, but every fish killed should be used to provide the data. To collect the data, the Cleithrum Project relies on the most common handlers of muskellunge: anglers and taxidermists. In return for supplying biological data and the cleithral bone, participants are given information on the age and growth rate of the submitted fish. The Cleithrum Project is designed to be independent of geographical and political boundaries; many muskellunge populations are fished by both Canadian and American anglers, and fish are commonly mounted far from where they were caught.

 The Cleithrum Project is based on the cleithral bone, part of the pectoral girdle of fish. The cleithrum is the only valid method for assessing the age of old, slow-growing trophy members of the pike family, especially muskellunge. Scales commonly fail after sexual maturity is reached.