Biological Survey — Erie-Niagara Watershed 



21 



In the extreme left hand eohimn (Table 1) one will find various 

 stream widths from 1 to 10; in the other columns, numbers indi- 

 cating the number of 3-inch fingerlings recommended for the vari- 

 ous stream widths. These latter are based upon various combina- 

 tions of pool values designated by the capital letters A, B and C, 

 and food values, by 1, 2 and 3. Thus (Al) indicates the very best 

 pool conditions and the highest degree of nutritive richness. Should 

 this combination occur in a stream whose average width is 5 feet, 

 one would recommend an annual planting of 720, 3-inch fingerlings 

 per mile. 



Temperature in Relation to the Distribution of Trout. — 



One of the most difficult problems a stream surveyor has to meet, is 

 the interpretation of water temperatures in relation to the suita- 

 bility of streams for trout. AYe know from observations on central 

 New York streams and from careful experiments conducted in the 

 hatchery that 75° F., is just below the highest temperature that 

 the native brook trout may endure. This of course presupposes 

 that waters of that temperature are free from deleterious sub- 

 stances and that the gaseous content is satisfactory. It has been 

 learned also that 80° F., is pretty close to the limit for brown and 

 rainbow trout and of the two species, the rainbows seem to stand 

 a slightly higher temperature than the browns. It therefore 

 becomes a very important matter to know whether a stream on the 

 hottest summer days will show temperatures exceeding these limits. 



If one were studying a very few streams, it might be possible to 

 ascertain this without difficulty by visiting them on the few days 

 that maximum air temperatures prevail. In a survey of a large 

 area, this is not possible, because our hottest days are not numer- 

 ous. It becomes necessary therefore to estimate maximum water 

 temperatures from records made on moderately warm days. 



For this purpose Tables, 2 and 3, taken from the Oswego survey, 

 were used, the first for regions below 1,000 feet elevation in wdiich 

 summer air temperatures may reach 96° and 98° F., and the other 

 for elevations upward to about 1,900 feet where the maximum air 

 temperatures range from 88° to 90° F., since the streams of the 

 Erie-Niagara watershed were found at various elevations from 573 

 up to about 1,900 feet, both tables were very useful. 



Table 2. — Relation of Air and Water Temperatures in Trout Streams 

 Located in Open Country up to 1,000 Feet Elevation 



Max, air temp. deg. Fahr 



Max. water temp., brook trout 

 Max. water temp., 



Brown trout 



Rainbow trout 



94.0 

 75.0 



79.0 



