FOOD FOR YOUNG SALMONOID FISHES. 845 



It will be noted that in this statement not only is the general average weight 

 of the larvse-fed fish 91 per cent higher than that of the meat-fed fish, but the 

 best of the 7 lots of meat fish was m.aterially below the poorest of the 6 lots of 

 larvse fish. 



Other data might be cited, but the above will suffice to demonstrate that 

 for increase of size of young fish, fly larvae constitute a far superior food to 

 chopped meat. There is reason to believe that the superiority does not end 

 here, but extends to the quality of the growth — that it induces a more healthy 

 condition of the tissues and functions of the fish, among other functions especially 

 those of the reproductive organs. A demonstration of the correctness of this 

 view must, however, wait for further experiment. 



Fly larvae are available for use during the greater part of the year. The 

 blow-fly {Calliphora) was found engaged in egg laying as late as November 24. 

 They have been actually used at Craig Brook as early as June and through the 

 autumn and winter and as late in the spring as the month of April. For winter 

 use, meat well stocked with very young larvae, or even with unhatched eggs, is 

 stored in pits or cellars where development can be retarded or hastened, as may 

 be desired, by changes of temperature. In this way sufficient larvae were kept 

 during the winter of 1889-90 to feed, exclusively, nearly 10,000 young salmon 

 to April 20, inclusive, with a loss of less than i per cent between December and 

 May. 



The materials which can be used in this work are sufficiently abundant and 

 accessible in most locaUties. Among them may be mentioned the refuse of all 

 sorts from slaughterhouses and fish markets, the refuse fish taken by all classes 

 of fishermen, domestic animals dying from accident or old age, especially old 

 horses, etc. 



The cost of fly larvae comes mainly from the labor involved. On one 

 occasion it was found that 40 pounds of horse meat, costing 40 cents, produced 

 8 quarts, or 16 pounds of larvae, the material costing thus about 3 cents for a 

 pound of larvae. It has been found that the mean cost of the labor through an 

 entire season was 7.3 cents per pound of food. Both labor and materials there- 

 fore cost 10.3 cents for a pound of larvae. 



One important feature requiring mention is the evil odor generated in the 

 process. However fresh and unobjectionable the materials may be when exposed 

 to the flies, they become, if handled in the usual way, exceedingly malodorous 

 before the larvae have completed their growth. This is sufficient to forbid the 

 location of the work near human habitations unless some means can be found to 

 suppress the odor. It is claimed that this can be done by the use of smoke. It 

 is also quite possible that the nuisance can be largely abated by the use of earth 



