THE SALT-WATER FISHERIES OF BOIIUSLAN. 101 



From what has hitherto been known, it will bo e^'ident that tlie her- 

 rings can certainly go as dee]) as 100 fathoms, but that they must never- 

 theless be considered as "surface-fish," which, according to accidental 

 physical canses, change the comparatively short distance from the sur- 

 face at which they generally live. The circumstance that the herrings, 

 when near the coast, often go into deeper water, might possibly be 

 ascribed to the milder Avinter temperature and to the cooler summer tem- 

 ]>erature, as well as to the greater calm and shelter which the deep waters 

 doubtless offer. AVhiLst spawning, the herrings must, of course, go to- 

 wards the bottom. 



38. Although there may be very small schools of coast-herrings, com- 

 posed of stationary fish, the herring must, in a general way, be consid- 

 ered as an entirely migratory Jish. 



From the fact that the herring is a surface-fish, it almost necessarily 

 follows that the migrations of the herring generally go in a Jiorizontal 

 direction, an opinion, however, w^hich science has only reached quite re- 

 cently; for, according to Anderson, Nihson, Axel Boedc, and several other 

 naturalists, the migrations of the herring go in a vertical direction, hav- 

 ing for their object a ditierent depth of water with varying pressure and 

 temperature. 



With regard to a certain region, the migrations of the herring may 

 be specially directed towards this region, or they may only pass through 

 it, in W'hich latter case the herring would only be a Jish-of-jmssage as far 

 as that region is concerned. 



The herrings which visit a coast are, with regard to the object of this 

 visit, either herrings which seek a spawning-place or herrings which 

 seek food, in which latter case their coming and going is less regular 

 and more dependent on i)hysical conditions.''^ 



With regard to the season when the herrings visit the coast, they are 

 divided into winter-herring, spring-herring, summer-herring, or autumn- 

 herring. 



The sea-herrings generally \isit the coast only once a year, but some- 

 times also twice. 



With regard to the steadiness of the herrings' visits to a certain coast 

 the herrings must be considered regular migratory fish, as far at least as 

 the extent of coast is not too much limited, and not too much regard is 

 paid to the irregularities of those herrings which come in search of food ; 

 but the very large schools of sea-herrings may also, as will be shown 

 below, be considered as periodical visitors to the coast — such periods 

 extending over eighty to one hundred years. 



39. With the exception of those parts of the day when the herring is 



6' This circumstance lias given rise to the often quoted and misunderstood saying of 

 MaeCidloch that the herring is "an apparently most capricious fish." (Quarterly 

 Journal of Science, Literature, and the Arts, XVI, No. XXXII, London, 1824, p. 214.) 

 Most of the instances of the capriciousness of the herrings seem to have been taken 

 from the herring-fisheries on the western coast of Scotland, which have for theirobject 

 only herrings which have come in search of food. 



