NATIONAL FISHERY CONGRESS. 
361 
the ocean, and of the peculiar difficulties which have to be overcome, it seems unlikely 
that propagating operations conducted at a few points along the shore can ever reach 
that magnitude demanded in order to make them effective. 
The conclusions arrived at may be summarized in the following propositions: 
1. The total mackerel supply has not been proved to have diminished materially 
within the present century. 
2. The abundance of mackerel has varied greatly within the area of operation of 
the American Ashing fleet. 
3. The minor annual variations in the catch are in part due to the local migration 
of the schools, and in part to the activity with which the fishery is prosecuted. 
4. The more important fluctuations are of long interval, and may be represented as 
waves of elevation and subsidence having a period, during the present century, of 
usually 20 years. They are normal, in the sense of being independent of the fisheries. 
5. The causes of these more important fluctuations are not fully known, but the 
most probable which have been suggested are, first, extensive migrations which carry 
the body of the fish to and from our shores, and second, variable fecundity. These, 
again, are the result of complex cooperating factors, some known and some unknown. 
6. The need is, therefore, not to increase the total number of mackerel, but to 
render available a uniform portion of the supply each year, or at least to furnish a 
means of forecasting the prospects of each season — that is, to determine the laws of 
this periodicity. 
7. The method of artificial propagation, even if successfully conducted, is not off 
proved utility for the mackerel. 
8. If artificial propagation is to be of any benefit, it must be practiced on a vast 
scale, commensurate with the great area over which the American school of fish roams. 
9. Owing to the capricious roving habits of the mackerel, it is doubtful if local 
schools could be established and maintained by the deposition of artificially-hatched 
fry in the desired localities. 
10. With our present knowledge of the subject, the mode of procedure which 
promises the best practical results with the least expenditure would be to deposit in 
the water immediately after fertilization the enormous numbers of eggs which can 
frequently be obtained from spawning schools captured in purse seines. This would 
at least avoid the most serious injury which falls upon the mackerel as a result of the 
modern methods of fishing. 
11. The problem of the mackerel can not be divorced from the problems of pelagic 
life in general. When the latter are solved the former, together with many other 
practical fishery problems, will disappear. The scientific labors of the Fish Commis 
sion and of individuals have accomplished much toward this end, but much more 
remains to be done. In the specific case of the mackerel there is scarcely an important 
question of its economy upon which fuller knowledge is not required for the practical 
benefit of the fisheries. 
University of Pennsylvania, Philadelphia. 
