15-1 1). Although histidine and methionine were present in greater amounts in 

 Diets 6 and 9 than in the other treatment groups, no relationship is obvious 

 between these amino acid levels and growth and survival. The higher amounts 

 of leucine in the brine shrimp fed fish could indicate a role of this amino acid 

 in their greater growth and survival. However, this was not evident in the 

 freeze-dried brine shrimp fed group. 



No substantial differences were found in growth and survival of fish fed the 

 nonsupplemented amino acid diet (Diet 8) versus the supplemented diet (Diet 

 9). Therefore, it is difficult to say the quantity of dietary amino acids influence 

 the metabolism and utilization of the various diets. Bioavailability studies will 

 be necessary to ascertain the degree of incorporation of the supplemented 

 amino acids. 



CONCLUSIONS 



1 . The best growth and survival of juvenile silversides was obtained on a live 

 3-day-old brine shrimp nauplii diet. Substantially lower growth and 

 survival was obtained on the artificial diets. 



2. Freeze-dried brine shrimp provided less growth than a live brine shrimp 

 diet. Live brine shrimp must contain some component which is removed 

 or altered upon freeze drying. 



3. It is difficult to say whether protein (amino acids) in the diets was a 

 factor in the differences in growth and survival of cultured fish fed the 

 artificial diets and the brine shrimp fed fish. The brine shrimp fed fish 

 did, however, contain higher levels of leucine than all other cultured 

 groups. Bioavailability studies will be necessary to ascertain the degree of 

 assimilation and incorporation of dietary amino acids. 



4. Whole body hpid fatty acid composition of cultured fish changed to 

 reflect the composition of their diets. Fish fed the brine shrimp diet had 

 higher fat levels and lower polyunsaturated fatty acid levels than wild 

 fish. Cultured fish appear to be storing large amounts of lipids in order to 

 obtain a threshold level of the polyunsaturated fatty acids. 



5. Fish fed a cod liver oil based diet more closely resembled their wild 

 counterparts. However, growth and survival were poor compared to 

 3-day-old brine shrimp fed fish. 



ACKNOWLEDGEMENTS 



The experimental part of the project required a close working arrangement 

 between scientists of the marine fish culture team at the Environmental 



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