SCHAEFER, J. T.*; SCHULTZ, E. T.: Scaling allometry of energy allocation to growth and storage in temperate populations of an annual fish, Pimephales promelas

The allocation patterns of acquired energy to growth or storage are subject to environmental factors and may be modified by evolution. Selective pressures on the allocation strategies of annual temperate fish are likely to be strong, especially where the growing season is short, the winter is long, and reproduction begins early in the spring. We studied the somatic composition of fathead minnows (Pimephales promelas) from three temperate ponds to elucidate energy allocation strategies. We predicted that both lean mass (a measure of energy allocated to growth) and lipid mass (representing energy devoted to storage) would be disproportionately high in larger individuals because of hyperallometric scaling on any single date, and would accumulate over the season. Our analysis indicated that patterns of tissue scaling differed between ponds and over time within each pond. Lean tissue at length accumulated over the season, but did not scale hyperallometrically. Lipid tissue did not clearly accumulate and scaling relationships generally were not hyperallometric. We conclude that fathead minnows do not have a strategy of storing energy in preparation for winter, and that environmental factors have a strong influence on the allocation of acquired energy in fathead minnows.