52 Conservation Department 



These trout had obtained a ration of this composition by taking 

 the following- natural foods in tlie percentages stated : 



Per cent 



Fish 2.52 



Insects 88.88 



(^rustacea 8.28 



Mollusca .27 



100.00 



Tlie high percentage of insect food is noteworthy. Naturally 

 it would be ex]iected that trout will be most abundant in those 

 parts of the stream which provide the greatest amount of such 

 food. It is not known how diverse fishes are in their protein, fat, 

 and carbohydrate requirements. It is quite apparent, however, 

 that different species differ widely in type of food organism. 

 Pickerel (Esox) feed largely upon other fishes; the stone roller 

 (Campostoma anomahim) subsists upon a diet of mud and 

 ''slime" containing very small plant and animal life. 



It is worthy of note here that young fishes differ from adult 

 fishes in type of food. A young bass {Micropterus dolomieu) 1 

 inch long, taken from Caneadea creek (Allegany county) July 6, 

 1926, had eaten 3 very young mayfly nymphs (Ephemerida), a 

 small species of fly (Diptera), 2 small midge larvae {Cliirono- 

 midae), and 5 tiny Crustacea (PhyUopoda and Copepoda). Adult 

 fishes of this species feed mainly upon crayfish and small fishes. 



(7) Shelter. — Certain species of fishes and the young of many 

 other species seem to require weed beds or some type of shelter. 

 A fish such as the golden shiner (Notemigonits crysoleucas) Is 

 most common among water plants, probably resorting there for 

 both shelter and food. In trout streams, pools affording shelter 

 of logs, roots and the like are usually more productive of fish than 

 are unsheltered pools. 



(8) Spawning Grounds. — All fishes show certain requirements 

 regarding ])laces to spawn. The optimum ty])e of breeding place 

 for small-mouthed black bass (Micropferns dolomieu) is shallow 

 Avater with gravel bottom. Many other fishes choose similar ]daces, 

 where there is less likelihood of silt and mud ''smotliering" tlie 

 eggs than there is in a muddy location. 



Comparatively little is known of the factors whicli iufluence the 

 presence and abundance of many of our common fishes. This is 

 a fertile field for stud.y. 



Fishes and Pollution. — Polluting of streams by man often 

 causes a decrcMse in fish life. In some cases fishes are ])oisone(l 

 directly by the dumping of a poisonous substance into a body of 

 Wfitei-. In others fishes ;ire snlTocnted dwv to ;i sei-ious reduction 

 of the oxygen content of the wntei', caused by the pi'esence of large 

 (juantities of milk wjisles oi- othei- orgjinie snl)st;inees. in still 

 othei- cases certain types of food oi-ganisnis are driven out by 

 ])ollution, aiul fishes which require these ])articular foods cannot 

 exist, even though the condition of the water itself may be good. 



