SALT- WATER FISHERIES OF NORWAY. 671 



the opiuion that these can ouly be a very small portion of the enormous 

 masses which come to the coasts of the North Sea. I have good reason 

 to suppose that the greater portion come from a greater distance, viz^ 

 from the Atlantic Ocean, chiefly by way of the Channel, and some along 

 the northern coast of Scotland. The largest mackerel fisheries are car- 

 ried on in the Channel, and several things seem to indicate that the 

 mackerel which are caught on the coast of Holland belong to the same 

 schools which have entered the Channel from the Atlantic. At the end 

 of July and the beginning of August, the very time when our mackerel 

 fisheries have closed, mackerel are, according to Lowe {Fauna Orcaden- 

 sis), seen in large schools near the Orkney Islands. These are, prob- 

 ably, schools returning from the coast. 



The next question to be answered is : " What are the conditions of 

 the regular visits which the mackerel pays to our coasts?" It is a fact 

 which should have been known long since, that the same phenomenon 

 which, at other seasons of the year, causes the coming of the spring- 

 herring and the codfish, viz, the spawning process, brings the mackerel 

 to our coast. Zoologists have hitherto had no idea regarding the pecu- 

 liar circumstances under which this spawning process is going on, no- 

 idea where the mackerel drops its roe, whether in shallow or deep places, 

 nor have they known anything concerning the development and further 

 growth of the mackerel. All these important points in the natural his- 

 tory of the mackerel have remained in the dark up to the present day^ 

 and this in spite of the mackerel's being one of the most common fish in 

 Europe. The cause of it is this, that ichthyologists have formerly 

 taken too little pains to study the mode of life of the different fish while 

 in the water, and have confined their investigations to the specimens 

 preserved in museums, or, at best, to dead fish which they had obtained 

 from some fisherman. In this way exact descriptions of fish may be 

 written, and diagnostic data given serving to separate one species from 

 the other, but all that important part of the natural history of fish, com- 

 prising their mode of life, their migrations, spawning, and development, 

 will remain in the dark. On these important points nearly all informa- 

 tion has been obtained from fishermen and other persons utterly ignorant 

 of zoology, and numberless erroneous ideas have consequently been ad- 

 vanced. 



The first preliminary investigations of the spawning of the mackerel 

 were made by me during one of my zoological tours, in the summer of 

 1865. During the journey I made this summer I had an opportunity to 

 supplement and corroborate my former observations. The mackerel 

 spawns on the surface of the water, sometimes near and at other times 

 far from the coast, without regard to the depth and the nature of the 

 bottom. The roe does not sink to the bottom as is the case with the 

 roe of the herring, but floats near the surface and there goes through 

 all the stages of its development. In this respect the mackerel resem- 

 bles closely the codfish and some other salt-water fish whose spawning 



