Reliability of Bioelectrical Impedance Analysis for Estimating Whole‐Fish Energy Density and Percent Lipids

Abstract

Abstract.-We evaluated bioelectrical impedance analysis (BIA) as a nonlethal means of predicting energy density and percent lipids for three fish species: yellow perch Perca flavescens, walleye Sander vitreus, and lake whitefish Coregonus clupeaformis. Although models that combined BIA measures with fish wet mass provided strong predictions of total energy, total lipids, and total dry mass for whole fish, including BIA provided only slightly better predictions than using fish mass alone. Regression models that used BIA measures to directly predict the energy density or percent lipids of whole fish were generally better than those using body mass alone (based on Akaike's information criterion). However, the goodness of fit of models that used BIA measures varied widely across species and at best explained only slightly more than one-half the variation observed in fish energy density or percent lipids. Models that combined BIA measures with body mass for prediction had the strongest correlations between predicted and observed energy density or percent lipids for a validation group of fish, but there were significant biases in these predictions. For example, the models underestimated energy density and percent lipids for lipid-rich fish and overestimated energy density and percent lipids for lipid-poor fish. A comparison of observed versus predicted whole-fish energy densities and percent lipids demonstrated that models that incorporated BIA measures had lower maximum percent error than models without BIA measures in them, although the errors for the BIA models were still generally high (energy density: 15-18%; percent lipids: 82-89%). Considerable work is still required before BIA can provide reliable predictions of whole-fish energy density and percent lipids, including understanding how temperature, electrode placement, and the variation in lipid distribution within a fish affect BIA measures.

Bioimpedance as a tool for evaluating the body composition of suruvi (Steindachneridion scriptum)

“…BIA has already been used to successfully determine the body compositions of different fish species (Cox and Hartman, 2005;Duncan, 2008;Andrade et al, 2014), although certain authors have argued that improvements remain necessary before BIA approaches can become a useful tool for fish farming (Bosworth and Wolters, 2001;Pothoven et al, 2008). We note that particular care (regarding room temperature and the position of needles, for instance) is required during BIA readings to minimize errors.…”

Reliability of non-lethal assessment methods of body composition and energetic status exemplified by applications to eel (Anguilla anguilla) and carp (Cyprinus carpio)

“…Thus, the quantity of water within fish flesh mainly influences the degree of resistance (Schoeller, 2000). Because body water is inversely related to body fat content as mentioned before (Craig, 1977;Schreckenbach et al, 2001) and hence water relates inversely to energy density (Chellappa et al, 1995), BIA measures have been found to correlate well with a range of body composition metrics in fish (e.g., Bosworth and Wolters, 2001;Pothoven et al, 2008;Hanson et al, 2010;Rasmussen et al, 2012).…”

“…All BIA measurements were triplicated, and the distance between the two sets of needles was measured. Raw BIA measurements (resistance and reactance) and parallel-transformed raw BIA measurements (Pothoven et al, 2008) are cross-sectional measurements and should relate to relative tissue properties like relative dry mass (Rasmussen et al, 2012), whereas volumetric measurements (e.g. needle distance 2 /parallel-transformed reactance, Cox and Hartman, 2005;Hanson et al, 2010) are three dimensional measurements and should reflect whole organism properties like total body water (Rasmussen et al, 2012).…”

“…In these applications water content in fish flesh is measured using electric currents [bioelectric impedance analysis, BIA, Cox and Hartman (2005)] or microwaves in handheld devices [fat meters, FM, Crossin and Hinch (2005)]. Calibration studies using BIA devices regressed various nutrients in fish flesh against BIA readings, in particular total body water, body fat, body fat-free mass, protein, and ash across a range of species (brook trout Salvelinus fontinalis Cox and Hartman, 2005;Rasmussen et al, 2012;steelhead Oncorhynchus mykiss Hanson et al, 2010; yellow perch Perca flavescens, walleye Sander vitreus, lake whitefish Coregonus clupeaformis Pothoven et al, 2008;channel catfish Ictalurus punctatus Bosworth and Wolters, 2001). It is worth noting that BIA cannot measure any of these variables directly (Schoeller, 2000).…”

Ichthyometry and electrical bioimpedance analysis to estimate the body composition of tambatinga

“…That study also revealed differences among the fish: it underestimated the energy density and the percentage of lipids in lipid-rich fish, and overestimated the energy density and the percentage of lipids in low-lipid fish. The different models included the following as independent variables: weight, total length, the resistance and reactance in parallel, and the relationship between the square of the length and the resistance in parallel (Pothoven et al 2008).…”