(73) 



Some valuable fishes may be found dependent on food too liable to in- 

 jury or destruction by man or nature, to make it worth while to cultivate 

 them, while others, equally valuable, may be proven to subsist on food 

 practically indestructible. 



Such species as eat mixed food^ so that, in case of scarcity of one kind, 

 another may be drawn upon, are evidently more promising, other things be- 

 ing equal, than those of a more limited diet. 



That a full understanding of the competitions among the fishes of a 

 stream or lake is necessary to anything better than guess-work in fish-cul- 

 ture, or an expensive and improvident trusting to luck, is evident at once. * 



The scavenger fishes, which, by devouring the filth of streams, help to 

 purify them, are doubtless worthy of recognition. Whether a filth-eating 

 fish is better or healthier food than a bird or a mammal of similar habits, 

 may, perhaps, be profitably discussed. 



An acquaintance with the subject sufficient for the purposes above 

 mentioned must, of course, include the whole life of the fish, at all ages and 

 in all seasons. It is not impossible, for example, that the draining of stag- 

 nant waters connected with a stream may unfavorably aifect some of its 

 fishes, by lessening the supply of Entomostraca, especially Cladocera, for the 

 food of the fry. 



So much may properly be said concerning the purpose and promise of 

 the research, to justify the labor given to it, — especially since the general 

 neglect it has received may seem to indicate that it is not worth elaborate 

 study. 



METHODS. 



The stomachs and intestines were taken out of the fishes just as these 

 came from the seine : were labeled with specific name, place and date, and 

 preserved in strong alcohol. They were afterward opened and the contents 

 examined (usually with the microscope). Notes were made upon the objects 

 found in each, as far as they were recognizable — the species being deter- 

 mined, if possible, otherwise the genus, family, order, or even only the class. 

 The contents of each stomach were then bottled separately in alcohol, 

 labeled and preserved for future verification and further study. The emp- 

 tied stomachs have also been kept for anatomical purposes, and as a means 

 of verifying the species. It was found unnecessary to remove the stomachs 

 of the minnows, as these were well enough preserved in the bodies of the 

 fishes themselves. 



* That fishes and land birds should ever come into competition, seems at fir.st 

 sight remarkable ; nevertheless some of the former eat lar^e numbers of land 

 insects which fall into the water. The supply of these would, of course, be limited 

 by the depredations of birds. 



