Table 15-8. Percent Survival and Weight Gain for Silversides 

 Cultured on Various Experimental Diets 

 (Modified from Beck and Poston (7))^'^ 



Weight Gain 

 mg % 



1 



2 



Diet #1 data only one replicate, diets 2, 4-9 are averages of two replicates. 

 Fish were 23 days old at onset of the study and were cultured for 23 days. 



percent) and the best weight gain (411 percent). Normal growth of the wild 

 fish has been estimated at 12 mm per month during the growth period (6). 

 None of the other diets gave an appreciable weight gain; in fact some groups 

 actually lost weight. With the exception of Tetra Marin, all the artificial diets 

 produced a relatively poor survival rate. 



Table 15-9 shows the fatty acid composition of the natural and artificial 

 diets. The effect of the dietary fatty acids on the cultured fish hpids is 

 presented in Table 15-10. The diet profiles and the respective cultured fish 

 profiles were quite similar. The cultured fish fed the cod liver oil based diets 

 (Diets 6, 8, 9) and those fed Diet 5 contained a much higher level of 22:6a;3 

 than the brine shrimp fed fish (Table 15-6 and 15-10) or the soybean oil fed 

 fish (Table 15-7 and 15-10). These fish more closely resembled their wild fish 

 counterparts. A lipid modification of the salmon diet had therefore effected a 

 biochemical change in the fish to a more "wild like" laboratory fish. The 

 replacement of the soybean oil in Diet 7 by cod liver oil (Diet 6) doubled the 

 survival level, however growth was only one-half as great. It is very difficult to 

 draw a direct correlation between the dietary lipid composition of the 

 various diets and survival, since the experimental design of this study was quite 

 unlike the classical nutrition experiments. 



The comparison of the amino acid profiles of fish fed the natural and 

 artificial diets indicated little variation between the treatment groups (Table 



225 



