RAPPORTS. XIV: EHRENBAUM — 4 — 



On thoroughly analysing a number of these catches — partly English, partly German — 

 for which it is possible to state the place of capture (see diagrams on p. 5), we find, that especially 

 in the northern part of the North Sea, mackerel are plentiful at the bottom during the months 

 of December— January on to May, whereas in the southern part of the North Sea they 

 are wanting during this time, appearing only in April— May and disappearing from the 

 bottom in the months 01 June— July, i. e. the spawning time, which may be observed in 

 any part of the North Sea and other northern waters. In the time following the spawning 

 season, the mackerel are completely wanting in the depth of the northern North Sea on 

 to the months of December — January, whereas in the southern and middle part of the 

 North Sea (including the Great Fisherbank), they are caught by the trawl in the time from 

 August on to November in varying quantities. In autumn then the mackerel keep partly 

 to the bottom, partly to the upper layers of the water, eagerly seeking for food at a time 

 when they want to recover from the exhaustion of the spawning, the schools probably 

 dispersing to a certain degree, as they may be able to find their food easier, if they do 

 not go about in dense masses. The food at this time mostly consists of young fish, 

 esp. sprats, herrings etc., and in a less degree of planktonforms, which are the favourite 

 food at other periods of the year, e. g. in spring; and the mackerel are accustomed to 

 follow these young Clupeoids up to the inlets and fjords of the coast. It seems to me, 

 that the wellknown peculiarities of the mackerel autumn-fishery are sufficiently explained 

 by these circumstances. Whilst in spring the fish generally form dense and compact 

 masses, which keep together during this season and give occasion for an easy fishery 

 with continuous results, the autumn mackerel are much more dispersed and irregular in 

 their appearance. It is maintained, that in many localities the autumn schools are devoid 

 of those large fish, that are taken in spring, and the fishery, though lasting longer, does 

 not yield such regular catches as in spring. 



It is obvious then, from the catches of trawl mackerel, that certain movements of 

 these fish can be followed within the range of the North Sea, the fish retiring to the 

 northern, deeper part in winter time and wandering south and south-easterly, while keeping 

 near to the bottom, in order to rise at the beginning of spawning time; there after they 

 disperse, partly near the bottom, partly near the surface, and disappear again in a northerly 

 direction, partly also westward towards the Channel, during the latter part of autumn. 

 The question however arises, if these mackerel stay within the boundaries of the North 

 Sea, so that we have to deal with a special North Sea mackerel, or if they form part of 

 a larger body of fish, that recedes further into the Ocean. I think there are three reasons 

 for adopting the latter eventuality: 1) the quantities of mackerel taken in the North Sea 

 by trawl are far from being as large as the quantities caught near the surface, 2) there 

 is generally a certain — however short — period in the year, i. e. the month of November 

 and part of December, when it is hardly possible to get trawl mackerel in the North Sea 

 at all in any quantities, 3) it is only recently, that trawl mackerel have been landed from 

 the North Sea in reasonable quantities, and the quantities may decrease in the course of 

 the next few years, just as they have been increasing since about 1906. 



As far as the Channel is concerned, things seem to be quite similar. Here also the 

 quantities of trawl-caught mackerel are quite varying, though there are some well-known 

 localities, where the mackerel are accustomed to shoal in winter-time at the bottom, that is 

 Start Point near Plymouth; and a comparable ground in the North Sea is Viking Bank. 



