Cobb. — Pike-Perch Propagation. 99 



Bureau of Fisheries. The hatchery on Rainy Lake has been 

 operated by men assigned to the work from the Bureau and 

 the same holds true of all spawning work connected with the 

 hatchery. One of their men has also operated the Otter- 

 tail hatchery. 



With all our work the fish can be saved in large numbers 

 only by rigid enforcement of our adequate laws. The con- 

 clusions arrived at from considering the notes on our work 

 as a whole might be of interest. 



Those streams, in which the water comes to a suitable 

 temperature for spawning before the ice is out of the lakes, 

 into which they flow, are the most desirable for spawning 

 operations. The spawners come up in a well defined run 

 and are ripe, or nearly so, v/hen taken. The best spawning 

 temperatures run from 45° to 50° preferably 46° to 48° 

 though eggs are taken at as high a temperature as 63°. 

 Eggs taken at the higher temperatures are as a rule poor. 

 Good hatches have been made from eggs subjected to a 

 temperature so low that slush ice has formed in the water, 

 and this in instances where eggs had already been taken. 

 Such conditions occurring when the run is on, invariably 

 drive the fish down stream and stop the run. 



We find that the egg bearing females will not ascend 

 above the first swift water in any numbers while the males 

 pass over rapids to a large extent. The females pass up and 

 join them after depositing their eggs. 



Below the rapids in Pike River we have found naturally 

 deposited eggs forming a mass from 6 to 8 inches. These 

 eggs were eaten by suckers during the night and another 

 mass deposited during the next day. This sometimes was 

 repeated for as many as three consecutive days. All efforts 

 to hatch eggs taken from this mass were a total failure. Not 

 one fish has been produced by such attempts. 



The presence of eggs to this extent took place some years 

 ago though even now there are places where the egg mass is 

 considerable. 



In most cases where an abnormally large loss has taken 

 place in eggs, indications have pointed to lack of care during 

 the hardening process. Rainy River is an exception to this 

 rule and here pollution is a determining factor. Lack of 

 care is generally the result of a sudden run producing more 

 eggs than the crew and equipment can care for in the 

 natural desire to secure the largest number of eggs possible. 

 The combination results in loss unless the men in charge of 

 the work have unusually good judgment. 



