156 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



From the above table it will be seen that upwards of 12,500,000 cod 

 eggs were fertilized, and that 5,000,000 young fish, or 40£ per cent., were 

 obtained from these. It will be observed also that the largest stock 

 of eggs possessed at one time was somewhat over 5,000,000, which was 

 merely one-eighth of the capacity of the establishment. Since it is not 

 difficult, with an abundant supply of parent fish, to hatch out two broods 

 in a year, the yield might be increased to about 80,000,000. 



When I heard the American fish-culturists, at the London Fisheries 

 Exposition last year, lament about the muddy water which they had to 

 use, I stated somewhat freely that the sea- water on the Norwegian 

 coast would be sufficiently clean for hatching purposes without filtering, 

 and, as a result of my opinion, 1 had it pumped directly into a reservoir, 

 from which it was afterwards conducted through wooden pipes and rub- 

 ber tubes to the apparatus. It was quickly apparent that this was a 

 great mistake, and that even very carefully constructed filters are 

 necessary for successful hatching. It is unquestionable that the sea- 

 water here is tolerably clear, but if we consider the fact that about 

 15,000 liters of water daily flow through each apparatus, and that the 

 bottom of the box is covered with wire gauze so fine that neither eggs nor 

 young fish can escape through it, we must realize that this gauze will 

 arrest all the dirt contained in the water and soon become so clogged 

 that the circulation will be greatly retarded. Moreover, if some of the 

 eggs, which float freely in the box during the process of development, 

 should from time to time come into contact with the bottom, these 

 also will soon be coated with mud and will sink to the bottom and be 

 destroyed usually within a few hours. The loss occasioned in this way 

 was at first considerable, but after the water became cleaner through 

 the use of tilteriug frames, and I, besides, had learned by experience 

 how to handle the eggs more carefully, there was an improvement, and, 

 towards the lastas high as50 j>er cent, of young fish were obtained. This 

 may indeed be regarded as very gratifying, especially when we consider 

 the fact that the Americans, who had all possible expedients at their 

 command, after a whole winter's work obtained a considerably smaller 

 average. 



The next difficulty which presented itself, and which caused a con- 

 siderable loss of eggs, was the circumstance that the sea-water some- 

 times contained so little salt that its specific gravity was less than that 

 of the eggs, which may be placed, with little variation, at 1.023. In 

 consequence of this the eggs fell to the bottom, and were securely held 

 there by the current, which has a downward movement as well as a ro 

 tary motion. It was possible, of course, to increase the saltness of the 

 water, but not without considerable expense, and to move tbe whole 

 establishment farther out to sea, to obtain Salter water, was naturally 

 not to be thought of, at least until other means had been tried to get 

 rid, if possible, more easily of this drawback, which for a long time re- 

 mained so serious that I even began to doubt the result. Naturally 



