REPORT OF COMMISSIONERS OP INLAND FISHERIES. \) 



THE FLUCTUATIONS IN THE NUMBER OF FISH ; AND THE NATURAL 

 CAUSES OF THEIR DEPLETION. 



The fluctuations from year to year and for indefinite periods 

 have been noted all along throughout the whole histor3^ of them. 



Often a great diminution without known cause has occured, 

 and also immense numbers appear without any known reason ; such 

 has ever been the case with fishes. 



These fluctuations were as clearly observed in the middle ages 

 as now, the increase and diminution then caused the rise 

 and fall of towns ; their settlement and opulence, as well as 

 their decay and poverty have been due to the increase or diminu- 

 tion of the fishes. In later times the changes have been no less 

 obvious and important. 



The influences that produce these changes upon our coast is of 

 especial interest to us. 



Unquestionably the great factor in producing the change in 

 numbers is amongst the fishes, the larger or best armed destroy- 

 ing the smaller or weaker. 



But those most reduced with us, are those that cast their spawn 

 in the fresh upper water of our streams. Some of these have been 

 so long absent, or their numbers so reduced that we hardly realize 

 that they once existed in great abundance in our waters. Of these 

 the most important are the salmon, shad, herring and bass. While 

 the influence of natural causes is suflicient to produce this change, 

 the generally accepted theory is that ^he depletion is caused by 

 the obstruction to streams, pollution of the water, and such as 

 arise from the development of the country. AVe incline to the 

 belief that this is the primary cause of the depletion of the anadro- 

 mous fishes. 



The appearance in ever varying numbers of the fishes that visit 

 our coast every season, affords room for much study, and no end 

 of speculative theory. 



Their history while absent is one of the uurevealed mysteries 



