NOTES ON THE REARING OF SALMON 



By H. B. Torrey and D. E. Lancefield, 

 Reed College, Portland, Oregon. 



I. 



Raw versus Cooked Beef Liver as Food. 



Finely ground beef liver has long been highly esteemed 

 by fish culturists as a food for salmon fingerlings, in 

 spite of its cost. The custom has been to feed it raw. 

 That this has been so is due partly to the widespread 

 belief that raw foods more closely approach the natural 

 food of the species in the wild state, and are accordingly 

 more satisfactory; partly because, in the absence of 

 definite tests, no good reason has appeared for assuming 

 the added expense of preparation which cooking would 

 entail. It is a common practice to soften refractory tis- 

 sues, such as the bones and cartilages of fishes, with su- 

 perheated steam. But this method of preparation would 

 be quite superfluous for beef liver, unless it could be 

 shown that cooking would actually increase the efficiency 

 of the liver fed. 



We have attempted to find a definite answer for this 

 problem. Our experiments are not concluded, so that the 

 results so far obtained must be considered tentative. 



The method of investigation consisted in dividing a 

 given lot of Chinook salmon that were just beginning to 

 take solid food through the mouth into two numerically 

 equal groups. These were placed side by side in separate 

 troughs, the flow of water, temperature and all other con- 

 ditions being as nearly as possible the same with the 

 single exception of food. One group was fed on raw liver, 

 the other on an equal daily weight of cooked liver. The 

 weight of twenty fish was taken at the beginning and at 

 the end of the experiment, the average weight per fish 

 obtained in each case and the average gain per cent, in 

 weight during the elapsed time. Four pairs of groups 

 are tabulated. 



