**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**

Chinook salmon stock composition in Lake Huron: using otolith microchemistry as a

natural marker of stream origin

Yolanda E. Morbey², Brian J. Fryer³, David Gonder⁴, James Johnson⁵

² Department of Biology, University of Western Ontario, 1151 Richmond St N,

London, ON N6A 5B7, Canada

³ Great Lakes Institute for Environmental Research and Department of Earth

Sciences, University of Windsor, Windsor, ON N9B 3P4, Canada

⁴ Ontario Ministry of Natural Resources, 1450 7th Ave E, Owen Sound, ON

N4K 2Z1, Canada

⁵ Michigan Department of Natural Resources & Environment, 160 East

Fletcher, Alpena, MI 49707, USA

November 2011

ABSTRACT:

Analysis of otolith microchemistry was evaluated as a technique to assign natal origin to Chinook salmon in Lake Huron. Chinook salmon fry were collected from 17 tributaries and 7 hatcheries in the Lake Huron watershed, and the elemental composition of their otoliths was analyzed using laser ablation inductively-coupled plasma mass spectrometry (ICP-MS). Linear discriminant function (LDF) models of otolith elemental composition showed very high classification accuracies. Models correctly classified 89% of fry to the type of rearing environment (hatchery vs. wild) and 87% of fry to their individual collection site. Strontium isotope ratios of otoliths did not perform as well, however they clearly differentiated fry from Precambrian Shield regions and fry from geologically-younger regions. Adults of unknown origin (n = 102) were collected from five regions within Lake Huron and their otolith cores were analyzed for elemental composition. When these data were applied to the LDF models, 86% of adults were predicted to be of wild origin. This value is similar to that estimated from a recent, large-scale marking study. Of the wild fish, 57% were predicted to originate from southern Georgian Bay, 27% from the North Channel, Manitoulin Island, and northern Main Basin regions, and 16% from the southern Main Basin region. Otolith microchemistry is a promising technique to assign natal origin of adult Chinook salmon and to study questions concerning their population structure in Lake Huron.