Lantry et al.: Electrical conductivity to estimate water content of Perca flavescens and Alosa pseudoharengus 



77 



82 



80f fBaietal. 1994) 



78 



76 



74 



72 



70 



68 



Red dnim 



* 

 * • 



  *« t 



0.75 



0.95 



1.15 



1.35 



1.55 



0.75 



1.15 



1.55 



1.95 2.35 



81 

 76 

 71 

 66 

 61 

 56 



0.5 1.0 1.5 



TOBEC/g 



2.0 



Figure 2 



Comparisons between standardized values of percentage water (water content/wet weight) and 

 total-body electrical conductivity (TOBEC/wet weight) for yellow perch, alewife, sunshine bass, 

 red drum, and channel catfish. Data for sunshine bass, red drum, and channel catfish are from 

 Brown et al. (1993). Bai et al. (1994). and Jaramillo et al. (1994). 



ations where nutritional status can be controlled (e.g. 

 in aquaculture) and electrolytic balance is given suf- 

 ficient time to equilibrate throughout all bodily fluid 

 (i.e. serum, cellular, and extracellular) compartments. 

 Our ultimate goal was to use our predictions of 

 water content to assess the energy content of yellow 

 perch and alewife. Our energy density relationships 

 (Rand et al., 1994; Lantry, 1997) use percentage dry 

 weight as the independent variable. Percentage dry 

 weight values calculated from predicted water con- 



tent did not, however, correspond to values calculated 

 from measured water content for any of the five fish 

 species used in TOBEC studies (Fig. 3). Our analy- 

 sis indicates that further evaluations of the use of 

 TOBEC to predict fish body composition are war- 

 ranted. Fish size should be constrained to narrow 

 ranges, and percentage water ((water content / wet 

 weight) X 100) between individuals of different con- 

 dition should be evaluated. By controlling fish size, 

 conductivity differences due to body geometry could 



