Surber. — Biological Sur^/eys in Minnesota. 235 



hand, when the water supply becomes reduced to a weak slug- 

 gish flow like the upper waters of Mill Creek at Chatfield, the 

 many barnyards situated along its course have a telling effect 

 and create conditions which aquatic life can not withstand. 



Other matters besides pollution have a tremendous influence 

 on the conservation of our fish life. One of them is the care- 

 lessness or indifference of owners of power projects along some 

 of our important streams. In one instance complaint had been 

 made of certain devastation of spawning beds in one of our rivers 

 which demanded investigation. Quite by accident it was found 

 that a far more serious offense was being committed weekly by 

 the owner of a large mill who every Saturday evening at 6 o'clock 

 shut down his turbines and conserved every ounce of water 

 until Monday at 7 a. m., in order to raise a head. In doing this 

 he exposed the active river bed for several miles below, and bass 

 and crappie nests were found high and dry, resulting in the 

 utter destruction of thousands of fish ; yet no one complained of 

 this, though they were up in arms over a matter doing less than 

 a hundredth part of the destruction caused by this mill owner 

 in cutting off the overflow at his dam. 



RESULTS AS APPLIED TO STOCKING OE STREAMS. 



As previously stated it appears that many waters have be- 

 come unfitted for certain fishes, but admit of the substitution of 

 an almost equally desirable species. For instance, certain brook 

 trout waters have become much warmer than formerly without 

 an appreciable diminution of the food supply ; in such waters 

 the introduction of the brown trout has met with signal success. 

 Another means of great saving in these changed waters has been 

 the determination of the available food supply for young fishes, 

 whereby a far more conservative estimate of the number such 

 a stream would actually support has been made and fry planted 

 in accordance therewith. Previous to a critical examina- 

 tion thousands of fry had been dumped into certain streams 

 where but little food existed, resulting in overstocking, and na- 

 turally ending in almost complete failure. We, therefore, see the 

 application of the results of these surveys has been the elimina- 

 tion of waste in the distribution of fry and the substitution of 

 suitable for unsuitable species. These two remedies, elimina- 



