Evaluation of a chinook salmon (Oncorhynchus tshawytscha) bioenergetics model Charles P. Madenjian, Daniel V. O’Connor, Sergei M. Chernyak, Richard R. Rediske, and James P. O’Keefe Abstract: We evaluated the Wisconsin bioenergetics model for chinook salmon (Oncorhynchus tshawytscha) in both the laboratory and the field. Chinook salmon in laboratory tanks were fed alewife (Alosa pseudoharengus), the predom- inant food of chinook salmon in Lake Michigan. Food consumption and growth by chinook salmon during the experi- ment were measured. To estimate the efficiency with which chinook salmon retain polychlorinated biphenyls (PCBs) from their food in the laboratory, PCB concentrations of the alewife and of the chinook salmon at both the beginning and end of the experiment were determined. Based on our laboratory evaluation, the bioenergetics model was furnish- ing unbiased estimates of food consumption by chinook salmon. Additionally, from the laboratory experiment, we cal- culated that chinook salmon retained 75% of the PCBs contained within their food. In an earlier study, assimilation rate of PCBs to chinook salmon from their food in Lake Michigan was estimated at 53%, thereby suggesting that the model was substantially overestimating food consumption by chinook salmon in Lake Michigan. However, we con- cluded that field performance of the model could not be accurately assessed because PCB assimilation efficiency is dependent on feeding rate, and feeding rate of chinook salmon was likely much lower in our laboratory tanks than in Lake Michigan. Résumé : Nous avons évalué en laboratoire et en nature le modèle bioénergétique Wisconsin chez le saumon quinnat (Oncorhynchus tshawytscha). Des saumons quinnat gardés dans des aquariums de laboratoire ont été nourris de gaspa- reaux (Alosa pseudoharengus), leur nourriture principale au lac Michigan. Durant l’expérience, nous avons mesuré la consommation de nourriture et la croissance des saumons quinnat. Nous avons aussi dosé les concentrations de biphé- nyles polychlorés (BPC) chez les gaspareaux et chez les saumons quinnat au début et à la fin de l’expérience afin d’estimer en laboratoire l’efficacité de la rétention des BPC par les saumons à partir de leur nourriture. D’après notre évaluation en laboratoire, le modèle bioénergétique procure des estimations justes de la consommation de nourriture chez le saumon quinnat. De plus, dans cette expérience de laboratoire, nous avons calculé que le saumon quinnat re- tient 75 % des BPC contenus dans leur nourriture. Dans une étude antérieure au lac Michigan, nous avions estimé à 53 % le taux d’assimilation des BPC par les saumons à partir de leur nourriture, ce qui laisse croire que le modèle surestimait considérablement la consommation de nourriture dans le lac. Toutefois, nous croyons que la performance en nature du modèle ne peut être vérifiée avec précision, parce que l’efficacité de l’assimilation des BPC est reliée au taux d’alimentation et que ce taux chez le saumon quinnat est vraisemblablement beaucoup plus bas dans les aqua- riums du laboratoire que dans le lac Michigan. [Traduit par la Rédaction] Madenjian et al. 635 Introduction Alewife (Alosa pseudoharengus) invaded Lake Michigan during the 1940s (Wells and McLain 1973). Declines in the abundance of several fishes, including yellow perch (Perca flavescens), deepwater sculpin (Myoxocephalus thompsoni), and emerald shiner (Notropis atherinoides), in Lake Michi- gan during the 1960s have been attributed to the alewife in- vasion. Alewives have been suspected of interfering with reproduction of these native fishes by feeding upon their pe- lagic fry (Wells and McLain 1973). Coho salmon (Onco- rhynchus kisutch) and chinook salmon (Oncorhynchus tsha- wytscha) were introduced into Lake Michigan during the 1960s to control the alewife population and to establish a sport fishery (Tody and Tanner 1966). Other salmonines, in- cluding rainbow trout (Oncorhynchus mykiss), lake trout (Salvelinus namaycush), and brown trout (Salmo trutta), have been stocked into Lake Michigan since the 1960s as well. Stocking of salmonines appeared to be not only effec- tive in reducing alewife biomass during the 1970s and early Can. J. Fish. Aquat. Sci. 61: 627–635 (2004) doi: 10.1139/F04-033 © 2004 NRC Canada 627 Received 18 July 2003. Accepted 13 January 2004. Published on the NRC Research Press Web site at http://cjfas.nrc.ca on 31 May 2004. J17649 C.P. Madenjian, 1 D.V. O’Connor, and S.M. Chernyak. U.S. Geological Survey, Great Lakes Science Center, 1451 Green Road, Ann Arbor, MI 48105, U.S.A. R.R. Rediske and J.P. O’Keefe. Grand Valley State University, Annis Water Resources Institute, 202 Lake Michigan Center, 740 W Shoreline Drive, Muskegon, MI 49441, U.S.A. 1 Corresponding author (e-mail: chuck_madenjian@usgs.gov).