CONDREY, GOSSELINK, and BENNETT: SHRIMP DIETS 



Oxidizable carbon analyses were by the wet di- 

 chromate procedure of Johnson (1949) as re- 

 viewed by Strickland and Parsons (1968). Glu- 

 cose was used as a standard. The limitations 

 of this method are discussed by Johnson (1949) . 

 Total nitrogen was determined by a micro- 

 Kjeldahl technique with ninhydrin color devel- 

 opment; lipids in terms of fatty acids by sapon- 

 ification followed by complexing with pinacya- 

 nol; and carbohydrates in terms of glucose using 

 the anthrone reaction. Methods are those de- 

 scribed by Strickland and Parsons (1968). Pro- 

 tein was estimated by multiplying the nitrogen 

 values by 6.25. 



Ash-free dry weights were determined from 

 samples heated to dryness after addition of 1 ml 

 of nitric acid and then ignited at 500°C (2 hr). 

 For the defined diets (i.e., diatom, detritus, AF-1, 

 and Trout Chow) , F' values were obtained from 

 samples treated in this manner. Because of 

 small sample size, accurate determinations of 

 ash-free dry weight could not be made for fecal 

 material. Therefore E' was calculated from 

 oxidizable carbon in the feces, assuming that the 

 ratio of total organic weight to oxidizable carbon 

 {R) determined for the food was true also for 

 the feces. Markedly diflferent diets yielded a 



ratio of oxidizable carbon to organic weight of 

 1.92 to 2.33 (Table 2). This gives an estimate 

 of the likely error involved in the assumption. 

 Insufficient material was obtained from the algal 

 mat for ash-free dry weight determination of F', 

 and this value was estimated by multiplying the 

 oxidizable carbon concentration by 2. 



Analyses of variance were performed on the 

 raw data and are shown as standard errors of 

 the mean in the appropriate tables. 



RESULTS 



The effect of using 10 to 14 shrimp as a group 

 in each test was to average individual variation. 

 As shown in Table 3 variation in fecal analyses 

 among subsamples within the tests was extreme- 

 ly low, the coefficient of variation usually less 

 than 59r. Individual variability is shown in the 

 results of the feeding study on a natural algal 

 mat (Table 8). In this test, the substrate pre- 

 sented to the shrimp was not homogeneous. The 

 coefficient of variation of U' for individual 

 shrimp fed on diets ranging from 20 to 31^^ 

 oxidizable carbon was 16 Cr. 



Comparison of total organic concentration to 

 the sum of protein, lipids, and carbohydrate re- 



Table 2. — Chemical analyses of defined diets. 



1 Figures are mean values from 2-8 determinations ± standard error. 



Table 3. — Chemical analysis of feces produced by shrimp fed on defined diets. 



1285 



