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Shelby D. Gerking 



index of the efficiency of the growth process because protein 

 synthesis is the most characteristic feature of growth in 

 animals. The fat content of fishes varies considerably from 

 one individual to another and during the seasons of the year. 

 Such large variations in fat complicate precise growth measure- 

 ments based on body weight, dry weight, or caloric content. 



LONGEAR SUNFISH 

 olO-DAY EXPTS. 

 • 50-OAY EXPTS. 



BLUEGfLL SUNFISH 



DRY WEIGHT IN GRAMS 



Fig. 1. Relationship between efficiency of protein utilization and dry 

 weight of four species of fish. Sources of information given in text. 



With the exception of the angelfish, the other four species 

 fit a common pattern. The efficiency of protein utilization for 

 growth decreases as the fish increase in size (Fig. 1), indicating 

 that either size, age, or both affect the ability of the fish to 

 utilize their food for the synthesis of new protoplasm. The 

 angelfish is a special case because of its herbivorous feeding 

 habits. They were unable to grow on a diet of algae and 

 generally had a negative nitrogen balance. Menzel concluded 

 that angelfish cannot grow on a diet of plants alone unless they 



