INVESTIGATION OF RIVERS AND LAKES. 73 



These are by no means all the faets which should be observed, recorded and 

 studied. 



That there is great necessity for accurate observation in these matters is evident 

 from the different opinions expressed by different gentlemen regarding - the menhaden 

 yesterday. The truth is, we have very little exact information regarding the life- 

 history of the menhaden, and have but little if any more about any of our fresh- water 

 fishes. We possess some facts, it is true, and upon these few facts we have based 

 broad generalizations; but are they warranted by the facts? For example, we know 

 that vast quantities of sawdust and vast amounts of refuse from paper-mills and 

 other factories are let into our streams, aud we know, perhaps, that great mortality 

 has occurred with the fishes in some of those streams; but do we know that the one 

 is the cause of the other f We think that sawdust injures the fish, but do we know it? 



In conclusion let me say that the whole subject of the relation aud interrelation 

 of the various animal aud plant forms found in our waters, their action and reaction 

 upon each other, and their relation to the physical as distinguished from their bio- 

 logical environment, is the subject which is demanding investigation and upon whose 

 investigation must depend all important advance in fish-culture and fishery legislation. 



