142 



U. S, BUREAU OF FISHERIES 



ever, that any such conchisions must be left open to revision or 

 modification, since future experience may show that in some respects 

 our results may have been misleading. 



As previously pointed out we have no yardstick by means of 

 which we can compare with preciseness the results obtained in J 



5.5 



5. 



^4.5 



?4. 



»- 

 X 



S3.5 



•<3 



> 

 H2.5 



cc 



UJ 



^ 1.5 



\ 





o 



^e 



Nl N2N3N4N5N6N7N8N9N10NIIN12N13NI4N15N16N17N18NI9NZON2I 

 LOT NUMBER 



30 

 25 

 20 

 15 

 10 

 5 

 



FiGDRB 10. — Comparative erowth and mortality of brook trout fingorlings on experi- 

 mental rations, April 20 to September 24, 1929. Since the fish in the various lots 

 were approximately the same size on April 20, comparisons are based on average, 

 individual weiglits at tlie close of the experiment. Shaded columns indicate aver- 

 age individual weight in grams at close of experiment. Cross-hatched columns 

 indicate total mortality during the course of the experiment. The rations of the 

 individual lots were as follows: Nl = heet liver, 50; beef heart, 50. ^2=beef 

 melts. 100. NS=beef melts, 50; beef heart, 50. iVi = beef liver. 50; clam meal, 

 50. A'.5 = beof liver, 75: dry clam meal, 25. A'6" = beef liver, 50; clam meal, 25; 

 shrimp meal. 25. N7 = beef liver, 50; haddock meal, 50. .V8 = beef liver, 50; 

 shrimp meal, 50. 2V9 = beef liver, 50; haddock meal, 25; shrimp meal, 25. NJO = 

 beef liver, 75 ; dry buttermilk, 25. Nll=heet liver, 40 ; " consolidated " buttermilk, 

 60. A'/2 = beef heart, 85; dry skim milk, 15. N13=beef liver, 75; dry skim milk, 

 25. A'/.} = beef liver, 25; beef heart, 25; clam meal, 50. 2VJ.5 = beef liver, 50; 

 pilchard meal, 50. Nlfi = he('f melts, 50; clam meal. 50. A'/7=beef melts, 50; 

 clam meal, 25; shrimp meal, 25. A'/S = beef melts, 25; beef heart, 25; clam meal, 

 .50. .V/.9 = pig liver, 50; clam meal, 50. N20=pig liver. 50; clam meal, 25; shrimp 

 meal, 25. V3/ = pig liver, 25; beef heart, 25; clam meal, 50 



different years or even during the same year under somewhat differ- 

 ent conditions. Attempts to rate the various rations on a strictly 

 statistical basis have not proved satisfactory, since there are many 

 variable factors involved which can not be successfully subjected 

 to mathematical analysis. Any ration to be satisfactory should 

 result in rapid growth and low mortality, but the comparative 



