210 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



very rapidly, the same should also be the case with the fish-of-prey. 

 But on the other hand we seem justified in supposing with Kroyer and 

 JV^ W. Mahn, that a decided increase or decrease of fish-of-prey may 

 cause a temporary decrease or increase of the herrings at least in some 

 of the smaller herring-fisheries. 



57. Lack of food has likewise been considered as a cause why herrings 

 have gradually left a coast. Leemoenliock already has considered the 

 varying quantity of food as the ijrincipal cause why herrings changed 

 their place of sojourn; but, as far as I know, this idea did not become 

 general untn the question of oU-refuse was discussed during the last 

 great Bohuslau fisheries ; '''* and when the herrings had ceased to come 

 to the coast of Bohuslau, a gradual decrease in the quantity of food was 

 assigned as one of the causes of this misfortune. This last-mentioned 

 opinion has, so far as the Bohuslau herring-fisheries are concerned, been 

 embraced by Prof. Q. 0. Sars. K we now suppose, with Professor 8mitt, 

 that the revival of the great herring-fisheries is owing to the accidental 

 arrival of a new "race of herrings," which increased at a rapid rate, it 

 is reasonable to suppose that this rapid increase produces lack of food, 

 and this explanation will seem more plausible than an increase in the 

 number of flsh-of-prej^ from the same cause. But even then it will be 

 difficult to explain why not all herring-fisheries are periodical, which is 

 certainly the case only with a few. This periodicity ought also to be 

 particularly noticeable with those herrings which come to the coast for 

 the purpose of seeking food, which is by no means the case. The theory 

 that the periodicity of the herring-fisheries is dependent on the varying 

 quantity of "herring-food," has been further developed by Prof. G. 0. 

 8ars, who supposes that the herrings are obliged to seek their food in a 

 certain regular order at a greater or less distance from the coast. By 

 means of this supposition, he endeavored to prove that the iTorwegian 

 spring-herring fisheries are not periodical in the proper sense of the 

 word, but that the occasional decrease of these herriags, or their staying 

 away entirely, is caused by the circumstance that at times these herrings 

 had to seek their food so far out at sea that they could only come to the 

 coast late in the season. They would, consequently, have to spawn im- 

 mediately on the very outermost bottom. The fisheries would, there- 

 fore, be short and insignificant.'^^ The circumstance that the Norwegian 

 summer-herrings continue to be very flourishing has also induced Pro- 



'•» About the same time, Prof. M. Strom had directed attention to the circumstance 

 that the ''herring-food" may be found in a i)lace one year and stay away the next, 

 and that the herrings would consequently have to follow it uj). Strom also mentions 

 that the small crustaceans, which princiiially compose the "herring-food," prefer the 

 currents of the sea, and that the varying direction of those currents may also cause 

 the crustaceans to change their x>lace, and conseqiiently produce new migrations of 

 the herrings. The wind may also have a good deal to do with all these changes. 



''^ According to Axel Boeck, it is an old opinion in Norway that the herrings, in the 

 intervals between the great fishery-periods, have not left the coast, but have only 

 transferred their spawning-places to inaccessible bottoms. This opinion has, however, 

 been almost entu-ely abandoned at the ]iresent time. 



