J. Appl. Ichthyol. 2017; 33: 3–12 wileyonlinelibrary.com/journal/jai | 3 © 2016 Blackwell Verlag GmbH Received: 26 April 2016 | Accepted: 26 May 2016 DOI: 10.1111/jai.13200 Summary The objectve of this study was to investgate lipid accumulaton and storage in age-0 and age-1 paddlefsh Polyodon spathula (Walbaum, 1792) in relaton to age, stock, year, and growth. Juvenile paddlefsh were collected from three locatons in North Dakota and Montana, USA, during July and August of 2011 and 2012 and proximate analysis was used to determine lipid content. RNA/DNA ratos were used as an index of growth rates. Diferences in age-based lipid accumulaton and storage in juvenile paddlefsh suggest a split allocaton between growth and lipid storage, with growth being the highest inital priority and emphasis on energy storage occurring at a larger size, later in life. Diferences in lipid allocaton between stocks indicate that allocaton is infuenced by hatchery/wild rearing conditons. Diferences within and between year-classes are consistent with feld evidence observed in 2012 of a strong 2011 year- class, and indicate that during productve tmes, paddlefsh may allocate energy to both body growth and lipid reserves, and that allocaton difers among years. The lack of a relatonship between RNA/DNA rato and lipid does not support a physiologically exclusive allocaton strategy between growth and lipid. Evidence from this and other studies suggests rather that an emphasis on growth, some energy storage, and a large rostrum size in relaton to overall fsh length in age-0 and age-1 fsh, may be adaptve in avoiding predaton while accruing necessary energy reserves for overwintering. Although this study also provides reference informaton regarding proximate compo- siton of wild and hatchery origin juvenile paddlefsh, much more study is needed into the relatonships among growth, low and high lipid groups, lipid allocaton in juvenile paddlefsh as well as the existence and tming of allocaton changes between growth and storage. To aid in understanding paddlefsh survival and year-class strengths, these relatonships also need to be linked to inter-annual diferences in early rearing environments for age-0 and age-1 fsh. 1 Western Fisheries Research Center, Columbia River Research Laboratory, Cook, WA, USA 2 Department of Fish and Wildlife Sciences, University of Idaho, Moscow, ID, USA Correspondence R. J. Hemingway, Western Fisheries Research Center, Columbia River Research Laboratory, WA, USA. Email: rhemingway@usgs.gov and D. L. Scarnecchia, Department of Fish and Wildlife Sciences, University of Idaho, Moscow, ID, USA. Email: scar@uidaho.edu ORIGINAL ARTICLE Energy acquisiton and retenton by age-0 and age-1 paddlefsh Polyodon spathula (Walbaum, 1792) in relaton to size, growth, and rearing conditons in two Great Plains reservoirs and hatchery ponds R. J. Hemingway 1 | D. L. Scarnecchia 2 1 | INTRODUCTION Characterizaton of energy acquisiton and use in a fsh species or stock is fundamental to understanding its life history, recruitment, and populaton dynamics. Energy acquisiton and use (primarily in the form of lipids) difer with age and conditon, as well as with external environmental conditons and selectve pressures (Adams, 1999; Olsen, 1999). As individual fsh develop from exogenous