Sample Preparation Techniques for Determination of Fish Energy Density via Bomb Calorimetry: An Evaluation Using Largemouth Bass

Abstract

We evaluated three homogenization and subsampling techniques for preparing fish tissue samples for bomb calorimetry to identify differences in efficiency for estimating fish energy density. We compared (1) drying the whole fish and homogenizing the dried fish tissue, (2) homogenization prior to drying and then drying the subsample of fish tissue, and (3) homogenization after autoclaving to soften the hard structures and then drying a subsample of the homogenized fish tissue. Sample drying time and energy density estimates were compared among techniques across a size range (wet mass = 32–1,080 g) of largemouth bass Micropterus salmoides. Both of the subsampling techniques reduced drying time by about 40% relative to drying the whole fish. All three methods provided statistically similar estimates of largemouth bass energy densities. The autoclave process was most efficient, minimizing both sample preparation time and drying time. Variance of energy density estimates was greater for both subsampling methods compared with the traditional whole-fish method. Thus, subsampling can decrease sample preparation time for bomb calorimetry but may reduce power to detect differences among variables of interest (e.g., season). Lastly, estimates of energy density for largemouth bass were a function of body mass, suggesting that using a constant energy density in bioenergetics models is not appropriate.