206 REPORT OF COMMISSIONER OP FISH AND FISHERIES. 



Following is a table sliowing the approximate time required for cod 

 eggs to hatch, with the water at the stated mean temperatures : 



Mean water tem- 

 perature. 



31° F 

 32° F 

 23° F 

 34° K 

 35° F 

 36° F 



No. of 



day.s. 



50 

 40 

 35 

 31 

 28 

 25 



Mean water tem- 

 perature. 



430 F 

 440 F 

 45° F 

 46° F 



47° F 



No. of 

 days. 



14 

 13 

 12 

 11 

 10 or 11 



Moderately clear water is essential to the healthy development of 

 the fry. If much sediment is present it collects on the eggs and acts 

 very injuriously, often killing them. Sometimes eggs become so coated 

 with sediment that the fry appear to be unable to burst the shell; 

 some lots of eggs thus affected have been known to retain fry fully two 

 weeks beyond the normal period of incubation. 



With eggs carefully taken and fertilized, and clear water of a 

 temperature from 41'^ to 47° F., it is possible t© hatch from 70 to 85 

 per cent of the eggs, but when the temperature gets below 38° the 

 percentage of fry hatched is only from 25 to 50, and the average for the 

 season is thus greatly reduced. The number of fry hatched is deter- 

 mined by deducting the losses shown on the hatching-cards from the 

 number of eggs originally in the box. One liquid ounce is estimated 

 to contain 10,524 eggs. 



CLEANING THE EGaS. 



Owing to the accumulation of sediment and other foreign matters in 

 the hatching-boxes, it is necessary to clean the eggs daily, running the 

 sound eggs from one box to another through a slot, the dead eggs 

 being left behind. The slots in the partitions dividing the hatching 

 compartments correspond with similar slots in the boxes ; they are 3 

 to 3J inches long and 1 J inches deep, and are placed 3 inches from the 

 front of the compartments. To begin the cleaning of a given row of 

 boxes, a glass slip is fitted into the slot between the second and third 

 boxes, the first box being left emj^ty for the purpose of receiving the 

 cleaned eggs from the second box. A wooden plug is then put in the 

 current hole at the back of the second box, and the siphon cap is 

 removed from the waste-pipe; this allows the box to fill with water, 

 and the eggs, undisturbed by the current, rise to the surface. The 

 water is allowed to enter the first box and to graduall}'^ fill it to the 

 level of the waste-pipe, and is then turned off. A plug is next put in 

 the waste-pipe of the box containing the eggs; the water rises till it 

 reaches the slot, and then runs over into the first box, carrying the good 

 eggs with it, while the dead eggs remain in the box. The regular water 

 circulation is then established in the first box. 



The inner box from which the good eggs have been removed is taken 

 out and the remaining eggs are washed into one end and poured into 



