164 BULLETIN OF THE BUREAU OP" FISHERIES. 



olliers togetlicr." It is ti'iie, of coiii'so, that tliere is a very nuiilvcd (lirtcroiicc in tli(> 

 rate of orowtli of trout, even under apparently the same food conditions. Trout 

 cidturists, for instance, tind it necessar}- to sort the young trout of a pond at reoular 

 intervals after the}' are a few months old, and separate the larger, precocious 

 individuals from the smaller, weaker ones, in order to keep the former from preying- 

 upon tiie latter. Hut. in spite of this apparent contradictory evidence, there is little 

 doubt that the great difference in the results otitained in the above experiment was 

 duf. in soHK^ measure at least, to the dili'ereut kinds of food supplied. 



As long ago as IG.oS Walton appreciated the importance of the ((uality of the feed- 

 ing ground, for he says: "And certainly, as some pastures breed larger sheep, so do 

 some rivers, by reason of the ground over which they flow, breed larger trouts." 

 Fran<as (18(!8) makes the assertion that "trout in one stream will be much larger, 

 tii-mer, redder, and better shaped than in others. This may, in a measure, be owing 

 to the greater al)undance of food, but I have evei'y reason to lielieve that it j)roceeds 

 quite as nuich from the kind of food that they are enabled to obtain." Further on 

 he says: " In lakes also it is a very common thing to tind the trout in one lake large, 

 bright, and well ferl and in another, very similar in appearance and perhaps onh* a 

 bare half mile distant from the other, they will })e long, black, and lean, with heads 

 out of all proportion to the thickness of the body. In another, probably but a 

 similar distance from the tirst two, the tiout will be abundant, but very small, though 

 Inight and well colored." To exemplify this he cites a group of small lakes in which 

 he had tished and attributes the superior condition of the trout in the smallest lake of 

 the group to the al)undance and greater variety of the food found in it. Baird (1857) 

 cites a similar ditl'erence lietween the trout of two streams, one of which is a tri!)utary 

 of the other, and he ascribes it to the great ditl'erence in the quantity and variety of 

 the fish food which he found in the two waters. 



Thus it is evident that a knowledge of both the quantity smd kinds of food found 

 in a stream or lake is of very great importance when it comes to the cpiestion of trout 

 culture. This, doubtless, is true also of the culture of all other fishes, and this 

 knowledge woukl l)e very valuable in the introduction of a species of fish into new 

 waters. If we know the kind of food on which the tish thrives best and if we also 

 know the i|uantity and kinds of food available in the water to be stocked, then the 

 proldem of stocking the water can be attacked in such a way as greatly to increase 

 the chances of success. Until such knowledge is acquired we must continue to 

 experiment more oi' less blindly. 



FOOD OF THE TROUTS. 



Walton tells us that the trout "lies at watch for any Hy or minnow that comes 

 near him; and he especially loves the May-Hy." In the two and a half centuries 

 since Walton wrote, relativel}' little has been added to his observations on the feeding 

 habits of most of the trouts, though several writers, especially writers on trout-culture, 

 have conuuented in a general way upon the great vai-iety of trout food. There is 

 very little definite information as to the quantities and proportions of the various 

 component elements, however. From general statements we learn that the food 

 includes various kinds of worms, all kinds of insects (both adults and larva'), moUusks 

 of one sort or another, crustaceans, small tish, tish eggs — in fact, almost anything 



