RAPPORTS. XIV: EHRENBAUM — 6 — 



From the observations made at the Irish coast and in the western part of the Channel 

 and from general considerations, the mackerel are not likely to go very far into the 

 Atlantic, but probably keep near the Atlantic slope, whence they approach, at 

 the end of March or beginning of April, wandering near the bottom and rising to the 

 surface, when near the Irish and Cornish coasts, sometimes also following the Channel 

 in an easterly direction and rising not before they reach the eastern half of the Channel 

 (e. g. Portsmouth), disappointing the fishermen, who wait for their appearance at the western 

 entrance of the Channel. 



If these considerations are reliable, then, of course, we have to deal with a single 

 race of mackerel, inhabiting the North European waters. The investigations 

 of Ch. Williamson on the races of the mackerel from the east and west coasts of Scotland 

 seem to endorse this supposition, and if the results of W. Garstang on the same subject 

 do not point in absolutely the same direction, it must be confessed, that the methods of 

 Garstang, who relies nearly entirely on the so-called "spottiness" of the fish, cannot be 

 looked upon as perfectly conclusive. 



Nevertheless Garstang is perfectly right, when he demonstrates the racial difference 

 of the North European mackerel from the American. This difference is so important, that 

 even the imperfect method of counting the spots and stripes in the colouring of the 

 mackerel is sufficient to prove it. I have been able to state this racial difference by quite 

 different means. Though the larval pigmentation of the American mackerel has never 

 been figured, it has been described by J. P. Moore, who studied the matter in the interests 

 oi an intended artificial propagation of the mackerel. From this description it is quite 

 obvious, that the pigmentation of the American form is, not widely but, so far different 

 from the European, that it is quite impossible to look upon them as one and the same 

 race. It is highly interesting also, that the larval pigmentation of the Mediterranean 

 mackerel differs in a similar way from the North European as the American does; the 

 pigmentation of the Mediterranean and the American form are very much the same. The 

 Mediterranean larva has been described and figured by E. W. L. Holt, and the doubt of 

 this author about the correctness of his identification of the floating egg has been nearly 

 completely removed by the French scientist L. Fage. The Mediterranean form differs from 

 the North European also in the size of the eggs and in the constitutional size of the fish, 

 which is much smaller in the Mediterranean. 



Thus, it may be considered as settled, that we have to deal with three different forms 

 of the common mackerel in the Atlantic and in the Mediterranean, without regarding the 

 related species Scomber colias. 



This statement, though simplifying the matter, cannot diminish our interest in the 

 question, how far the migrations of the mackerel usually extend. We may 

 expect, that this problem will be solved by the modern form of marking experiments. 

 These experiments however will not be easy, as we have to deal with a rather sensible 

 fish. Last summer by the kindness of Prof. Heincke, at my suggestion, a trial was made 

 with this method near Helgoland. 350 mackerel were marked by Dr. Weigold with 

 aluminium rings, put round the root of the tail ; no measurements were taken in order to 

 handle the fish as carefully as possible. As yet a single fish has been recaught on the 

 15. of October 1911, after a lapse of 273 months, near Dunkirk, on the French Channel 

 coast — a poor and yet a very interesting result ! It is my opinion now, that rings round 



