78 



Fishery Bulletin 97(1), 1999 



D 



35 

 30 

 25 1- 



20 

 15 

 10 



Yellow perch 



Perfect correspondence 



36 

 34 

 32 

 30 

 28 



15 20 25 



Sunshine bass 



30 



35 



26 



Perfect correspondence 



26 28 30 32 34 36 



38 



Channel catfish 

 36 



34 



32 



30 



28 



26 



24 



2^ 



35 

 30 

 25 

 20 

 15 

 10 



14 16 18 20 22 24 26 

 Red drum 



Perfect correspondence 



^ 



20 



25 



30 



35 



2 24 26 28 30 32 34 36 38 

 Actual %DWT 



Wet weight and TOBEC 

 Wet weight 



Figure 3 



Comparisons between actual and predicted values of percentage dry weight (dry weight/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). The line 

 in each panel represents the location of equivalence between actual and predicted. 



be reduced and wet weight could be eliminated from 

 prediction equations. 



Variability associated with the scanning equip- 

 ment, fish preparation prior to scanning, fish condi- 

 tion, and geometry offish within the scanner cham- 

 ber may generate errors too high to accurately pre- 

 dict ecologically significant changes in fish body com- 

 position. Analysis of TOBEC readings taken in fish 

 fed, fasted, frozen, and thawed in Bai et al.'s study 



(1994) indicates that both physiological and physi- 

 cal states affect conductivity values. Dehydration in 

 terrestial animals has also been obsen'ed to cause 

 disproportionate changes in TOBEC values (Wals- 

 berg, 1988). Our fish were frozen in water and prob- 

 ably were not dehydrated; however, the death of the 

 fish and the effect of freezing and thawing may have 

 altered conductance. Also, the potential existed for 

 exchange between body water and the water sur- 



