FOOD FOR YOUNG SALMONOID FISHES. 847 



resultant weights of these fish were not ascertained; but the record of losses 

 seems to indicate in a very positive manner that the food tested was quite 

 unfit for salmonoid fish to eat. 



In 1907 a test was made at the same station of the merits of Spratt's 

 "aquarium fish food" and" fibrine fish food." In submitting them for a 

 test, the general manager of the Spratt's Patent Company said: 



Our pure-food law guaranty serial number is 1632, and I wish to reiterate the state- 

 ment I have made previously, that the above-mentioned foods are purely meat, and 

 cereal and meat, respectively, and no preservative, coloring matter, or chemical, etc., 

 whatsoever, has been added to them. 



The aquarium food, it was understood, was in part cereal, the other wholly 

 meat. Both of them, as well as the food tested in 1905, were received directly 

 from the company. The fishes selected for the experiment were brook trout, 

 all derived from the same source. Six lots of 500 each were counted out to be 

 fed with Spratt's foods, and several other lots of equal size to serve as control 

 lots, and to be treated in various experimental ways. Three lots of 500 each 

 were to be fed with the aquarium fish food and three with the fibrine fish food. 



The experience of 1905 having indicated that it might be difficult to induce 

 fry to take these foods well from the start, the whole six lots were as a preparatory 

 step fed from May 20 to June 30 on finely ground hogs' liver, such as the other 

 fry and fingerlings at the station were receiving. On June 30, therefore, the 

 feeding of the Spratt's foods began, two of the lots receiving the aquarium food 

 and two of them the fibrine food, while the liver regimen was continued with 

 the other two until July 20. 



Of the four lots beginning the new food June 30, one was given the fibrine 

 food until October 1 9 and no other food ; another lot was given the same fibrine 

 food and liver on alternate days; a third lot received the aquarium food solely 

 until October 19; and the fourth lot received the aquarium food and liver on 

 alternate days. Of the two lots that continued to eat liver until July 20, one 

 was fed from that date until October 1 9 on the fibrine food and the other for the 

 same period on the aquarium food. All were fed three times daily. 



Of the other lots of trout derived from the same original source, two may be 

 regarded as control lots, numbered respectively, 1939Z' and I939Z^ Both of 

 these, consisting of 1,000 fish each, began to feed May 21, and were fed three 

 times daily through the season to October 9, hogs' fiver until the end of July and 

 hogs' plucks from that date to the close. 



All of these lots were treated alike, all in troughs fed by water of the same 

 quality, having trough room in proportion to their numbers at the start, the two 

 control lots of i ,000 each having troughs twice as long as the lots having 500 

 each. Two exceptions were made in favor of two small lots, 1939K' and 1939N', 



