360 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



or spermatozoan ; and while this is generally attributed to injuries received in capture, 

 attention may be directed to the suggestion that the periods of scarcity may be in part 

 due to lowered vitality and fertility of the fish. In this case it is obvious that to 

 attempt artificial propagation while the condition lasts would be a waste of time. 



But this explanation probably fails to reach the root of the matter, as a study of 

 the spermatozoa and eggs before and immediately after fertilization indicates, by the 

 activity of the former and the response of the latter, a good vital condition. Fertiliza- 

 tion is very easily accomplished, and the rhythm of development is strikingly constant 

 and simultaneous in all of the eggs of a batch. The unfavorable condition must be 

 sought in the method of propagation, and many facts point to the conclusion that the 

 shore waters utilized tor the purpose lack the physical qualities, and the apparatus fails 

 to supply certain important conditions requisite to the healthy development of the eggs. 

 To this conclusion are opposed the results reported from Gloucester Station, and these, 

 together with the partial success of experiments with water of increased density, lead 

 to the hope that the mackerel may some day be successfully hatched. 



There is, however, a further serious practical difficulty to be encountered. Even 

 were artificial propagation as successfully accomplished with the mackerel as with 

 the cod, and 50 per cent of the eggs handled turned out as fry, could the demands 

 imposed by the figures given above be met? During the season of 1890 the collection 

 of mackerel eggs was pushed with great vigor by the United States Fish Commission, 

 with the result that about 23,000,000 eggs were taken, a number which, even if all 

 were hatched and deposited under the most favorable conditions, would fall many 

 times short of producing 21,000,000 fish three years later. In 1897 less than 4,000,000 

 were obtained, although every effort was made to conduct operations on a large scale. 



These difficulties have led to the proposal that suitable arrangements be made 

 with the captains and owners of seining vessels by which one or more spawn-takers 

 (probably members of the crew would serve) would accompany each vessel during 

 the spawning season. Upon the capture of a spawning school vast numbers of eggs 

 could be taken, immediately fertilized, and turned overboard under the best natural 

 conditions for further development. 



The method has several obvious advantages (1) great numbers of eggs which 

 would otherwise be destroyed would be started on the way to future usefulness j (2) 

 it could be applied at small cost, and (3) in one respect it would be a gain over the 

 natural deposition of eggs, in that more certain fertilization would be insured. The 

 facts upon which this last statement is based are founded not upon investigations of 

 the mackerel, but of the cunner, where the gain is about 30 per cent. 



One disadvantage of the method would be that the eggs would be endangered by 

 contact with the waste thrown overboard during the splitting operations, and from 

 predaceous fishes thereby attracted. Moreover, in view of the above figures, it seems 

 futile to hope that operations could be conducted on a sufficiently large scale to be of 

 any considerable benefit. If it ever becomes possible to confine the fry until they 

 reach a considerable size, say until after they have assumed the adult form, then it may 

 be possible to secure the supply of eggs in this way, to transport them to a station 

 of great capacity and operating under conditions most favorable to the development 

 of the species, such as would be obtainable upon an ocean-going steamer or an 

 outlying island, and thus to bring about the desired result. But in view of the great 

 area covered by the wanderings of the mackerel, of the vast numbers which inhabit 



