[15] OPERATIONS AT THE NORTHVILLE HATCHERY. 1051 



obtainable, and ripens them at about the same time each season, there 

 being- but little fluctuation of temperature in these ponds at correspond- 

 ing periods of one year with another. 



The spawning season therefore opens almost invariably from the 1st 

 to the oth of November, and closes practically from the 10th to the 15th of 

 January, although much the greater portion of the fish spawn from the 

 middle of November to the middle of December. During the past 

 season, perhaps a half-dozen spawned later than the latest date men- 

 tioned, and from one of these eggs were not taken until February 2. 



Some 140,000 were taken altogether. The first 120,000 turned out 

 very well, a loss not to exceed 10 per cent, occurring during incubation; 

 but the last 20,000 showed a loss of 50 per cent., due to the plan of 

 handling the fish from which they were taken. A majority having 

 spawned, we placed the remaining fish in the raceway, and carefully ex- 

 amined them every morning. As a result of this repeated dipping up 

 and inspection of the fish for several mornings in succession, we were 

 compelled to pick away quite half of the eggs so taken — which is pretty 

 good evidence that the less the fish are disturbed or manipulated while 

 ripening, the better the eggs produced. 



The following statement accounts for the disposition of the eggs and 

 fry: 



Total number eggs taken 140, 000 



Loss during incubation 22, 000 



January 10, shipped to F. Mather, for reshipment to 



France 20, 000 



January 24, shipped to Druid Hill hatchery, Balti- 

 more, Md 30, 000 



72, 000 



Number frv hatched 68, 000 



March 8, planted in Washtenaw County, Michigan, in spring 



brook tributary to river Eouge 10, 000 



March 15, planted in spring brook near the Northville hatchery, 



and tributary to river Eouge 10, 000 



May 8, shipped per United States Fish Commission car, in 

 charge of J. F. Ellis 30, 000 



Loss on fry since hatching 8, 000 



Fry now on hand in nursery tanks 10, 000 



G8, 000 



Average j^eriod of incubation, 84 days. 



As our breeding force of brook trout will receive large accessions next 

 fall from the stock of growing fishes, we confidently expect to take at 

 least a half million eggs during the next spawning season. 



