MILNER FISHERIES OF THE GREAT LAKES. 33 



of eggs, the delicate nature of the embryo, and the numerous spawn - 

 oaters, effect a certain balance of numbers with relation to the general 

 fatuiiTB of tlie lakes, so that, up to the time of tlie early setth-ment of the 

 hike-region, the fish were found in great abundance. The nets now 

 came in as an additional agent in preventing the increase, the pound- 

 not, particularly, killing a large percentage of the fishes that had not 

 matured sufficiently to.assist the increase by depositing spawn, and in 

 consequence the numbers of fishes were rapidly reduced. 



The care of the eggs in the hatching-troughs has proved, beyond 

 question, the frail nature of the eggs of the white-fish. They are 

 smaller, and have a much thinner investing membrane, or shell, and have 

 not the same enduring vitality that the ova of the trout and salmon 

 have. So that in the open water of tlie lakes and rivers by far the greater 

 uuml)er are lost because of the disturbance of the bottom by the au- 

 tumn storms and the deposit of sediment fro;n the muddy water, the 

 failure of many of the eggs to come in contact with the milt of the male 

 lish, the myriads devoured by the army of spawn-eaters, and the addi- 

 tional evils of pollution of the waters from the drainage of cities, manu- 

 factories, and saw-mills, and the dragging of seines over the spawning- 

 beds. 



A quantity of white-fish eggs taken from the bottom of the Detroit 

 E,iver, a very extensive s{>awning-gTound, while dredging in company 

 with Mr. George Clark, at the close of the spawning-season, v,'ere found 

 to be dead and white, or so coated and stained with the black ooze that 

 they could not have survived. In the pond on Grassy Island, where as 

 many as ten thousand female white-fish deposit their spawn in a season, 

 we succeeded in taking between fifty and sixty embryo fishes, by draw- 

 ing a seine lined with millinet, and a diligent search through several 

 hours at the surface in the month of Aj^ril. 



In obviating all of these evils, artificial propagation asserts its ad- 

 vantage, and though the number of eggs that may be handled is ex- 

 ceedingly small compared with the millions sown by the fishes, yet the 

 number of fishes produced may really exceed the present production in 

 a state of nature. This assertion has amjile proof in the restoration of 

 fishes in regions where they have been nearly exterminated, and even 

 where no change was made in the restrictions upon the fishing that 

 might have assisted the increase. 



The experience of the past few years has proved entirely the possi- 

 bility of increasing the numbers of the white fish by artificial propa- 

 gation. The running water in the troughs supplies the conditions re- 

 quired by the eggs; the fertilization of the ova in the pan brings every 

 egg in contact with the milt ; thej- lie undisturbed and free from injuri- 

 ous sediment or filthy water ; the spawn-eaters have no access to them 

 whatever, and the dead eggs are immediately removed from contact 

 witli the living ones ; the young fish are under control in the troughs, 

 until the ovisac is ab*sorbcd, when they are ready to be placed in their 

 natural home, the cold waters of the northern lakes. 

 S. Mis. 74 3 



