Cobb. — Pike-Perch Propagation. 97 



age. After the eggs are eyed up they begin to adhere to 

 the extent of causing a poor circulation. A slight movement 

 with a feather will start the circulation again but the eggs 

 are so delicate that the loss is considerable and we never 

 secure a good hatch from these eggs though a nice percent- 

 age reach the eyed stage. We find that when these eggs are 

 retained in the water, where taken, this condition does not 

 exist. We now hold all the eggs at this collecting station 

 in the hatchery located on the river in which the run of pike 

 takes place. We are unable to advance any reasonable ex- 

 planation of the condition. It is only one of the many prob- 

 lems not talked about by writers on fish culture. 



Penning of fish is another problem capable of making 

 much trouble. We have been told that the welfare of the 

 fish while penned depended upon the circulation of water, 

 amount of oxygen, temperature and the number of fish con- 

 fined in a given space. We have had occasion to watch this 

 matter closely and fourteen years study has convinced me 

 that while the above conditions must necessarily affect the 

 fish, as they affect all life they are not the condition that 

 cause the most trouble in Minnesota. 



In 1910 I spent the entire spawning season on Rainy 

 River. Our main problem w^as holding the fish. At that 

 time tremendous numbers of large pike could be taken be- 

 low the rapids at Birchdale and some of them yielded from 

 two to two and one-half quarts of eggs. The average of all 

 fish stripped was about one quart. The water ran extreme- 

 ly high being about fifteen feet above normal summer level. 



Above the spawning grounds was a mile of rapids and 

 one mile below our pens were placed. This mile of water 

 was one rushing mass. Under these conditions there could 

 have been no lack of aeration and certainly no lack of water. 

 The temperature during the season was hardly above that 

 required for good spawning condition and sometimes below. 

 I placed the spawners in cribs made from netting and also 

 in pens made from boards. In some instances I closed 

 portions of the pens and left other portions free to circula- 

 tion so the fish could take their choice of current. I an- 

 chored pens in the current and also below the dock. Some 

 were crowded and some were nearly empty. The results 

 were the same in all cases no matter how placed and regard- 

 less of numbers. The fish showed signs of sickness the 

 second day. A pinkish color showed on the tail and also, 

 slightly, on the cheek. Another indication which I have not 

 mentioned elsewhere was a slight depression along the cen- 

 ter of the belly which seemed to be caused by a shrinking of 



