RESULTS OF BLUEBACK FEEDING TRIALS 



The first experiment was limited to trials in which blueback salmon 

 were used as the test animals. Both cold-water and warm-water trials were 

 conducted. In the cold-water tests no meals were included in the diets 

 except in specific instances where it was desired to determine toxicity. 

 All the diets that were carried through the additional 12-week warm-water 

 period, with the exception of the beef-liver control, were supplemented 

 with various dry meals. This supplementation was accomplished by a propor- 

 tionate reduction of the other components of the diet. 



A control diet of 100 percert beef liver (Diet 1) was included merely as 

 a basis for comparison with the work of other investigators in which beef 

 liver served as the control, and no reference has been made to this diet in 

 the comparison of results o 



The results of this experiment are summarized in table 1. 



Meal toxicity Tests 



This phase of the experiment was designed to determine whether a better 

 fortification with vitamins would reduce the mortality experienced when fish 

 meals were feed at cold-water temperatures. Burrows et al. (19%2) reduced the 

 mortality in meal-fed fish by supplementation with vitamins of trie B-complex. 

 While the reduction in mortality was significant, it was still not comparable 

 to the mortality encountered in diets without meal. 



In these tests the standard meat-viscera mixture (Diet 2) served as the 

 control and this combination supplemented with 10 percent salmon meal (Diet 

 3) as the index of toxicity. The meat-viscera-meal combination was fortified 

 with the vitamins of the B-complex plus A, C, D, E, K, inositol, and choline 

 at levels determined by Phillips (19^6) and McLaren et al (19U7) as ade- 

 quate for trout. Table 2 shows the levels of fortification used in Diet u. 

 In addition the meat-viscera combination supplemented with 5 percent meal 

 (Diet 5) was included to determine whether a lower meal level would still 

 produce a toxic effect. 



The mortality in the fish fed the 10 percent meal supplement (Diet 3), 

 when compared with that in the meat-viscera combination (Diet 2), was sig- 

 nificantly higher. The vitamin-fortified meal diet (Diet k) did not differ 

 significantly from the nonmeal diet. The meat-viscera combination supple- 

 mented with 5 percent meal (Diet 5) produced mortalities which, unlike those 

 in the fish fed 10 percent meal, were no greater than in those fed the con- 

 trol diet. The least mortality occurred in the control (Diet 2), the next 

 higher in the vitamin-fortified meal diet (Diet U), and the third highest 

 in the nonfortified 5 percent meal diet (Diet 5), and the highest in the 

 nonfortified 10 percent meal diet (Diet 3) as shown in table 1. A signifi- 

 cant difference in mortality was attained only between the meat-viscera 

 control (Diet 2) and the 10 percent meal supplerrent. 



