98 American Fisheries Society. 



the ovaries. Fish could not be held over the end of the 

 second day without loss. 



At Tower, which is one of our best stations, we were not 

 penning fish at all but seining, stripping those ripe, and re- 

 leasing the balance to be handled over again. In 1912 I 

 put in three weeks at this point and put in a trap and holding 

 pens. Conditions of the water were similar to those at 

 Rainy River but on a smaller scale. I was glad to learn, 

 that at this point fish could be held indefinitely and under 

 almost any conditions which could be desired. Loss from 

 penning at Tower has never occurred and none of the signs 

 of sickness have been in evidence. 



Other investigations have been carried on in other places 

 and though it will doubtless raise a question of scientific 

 reasoning I have found the following to hold true in every 

 case during my fourteen years service in Minnesota. Where 

 the run is composed of large yellow pike they cannot safely 

 be penned longer than from one day to the next. A run of 

 black pike can be held as long as desired and between these 

 colors the ability to stand penning very closely corresponds 

 to the degree of color. I will not try to explain this but hope 

 some time a scientific study of this subject can be made. Up 

 to this time I believe we have results from scientific reason- 

 ing which is altogether a different thing from scientific 

 study- 



I do not believe color would have any effect on fishes' 

 ability to stand penning but it does not follow that the con- 

 ditions which produced the color would not otherwise con- 

 trol the general life of the fish. 



One thing has held true in all cases where conditions are 

 such that fish return for the day to some point further down 

 the stream. When they are released below the net the 

 same fish return at dark and will continue to come to the net 

 night after night until ripe apparently suffering no harm. 

 It all leads me to believe that the cause of the trouble is in 

 the nervous system of the fish rather than in the physical 

 surroundings and that the condition which brings this out 

 strongest has a direct bearing on size and color. In any 

 event we have only experienced trouble where instructions 

 based on this theory have been disregarded. 



I have gone somewhat lengthly into the subject as it is 

 one of the most important questions with which we have to 

 deal. Were we able to pen and ripen the fish we could ex- 

 tend our work to almost any extent at comparatively small 

 cost. 



The work has been extended as rapidly as circumstances 

 would permit and in this we have been greatly aided by the 



