436 



NATURE 



[Afarck 15, 1877 



pier or jetty) has now been for the most part explained by the 

 surveys set on foot durirg our expedition. The "Storegg" 

 is nothing else than a piece of the edge of the extended barrier, 

 which in the west forms the boundary line beyond which lie the 

 cold polar sea-deeps. That so clear a knowledge of this edge 

 within a very limited extent has been already obtained, without 

 the least idea being formed as to its proper connection, naturally 

 arises from the polar sea-deeps here running in closer to the coast 

 than at any other point. A new piece of the continuation of 

 this edge had already been found by soundings made from the 

 steamer Hansteen, and we have now been able to establish its 

 existence at several other points, and that both farther south and 

 farther north it retires more and more from the coast to a distance 

 of from twenty to thirty Norwegian (140 to 210 English) miles. 



Although it may not be constant everywhere, it appears, how- 

 ever, to be the rule that at the bottom, at the farthest boundary 

 of the barrier, before it slopes towards the great depths lying 

 beyond it, it rises somewhat, and assumes simultaneously a hard 

 stony character, as is the case, as is well known, at the Storegg. 

 At the first sounding, when we went out from Husoe, we struck 

 this edge at about twenty Norwegian (140 English) miles' dis- 

 tance from the coast (stations i6 ^ and 17^). The boitoni, which 

 before had everywhere appeared to be sot, suddenly, at a depth 

 of 221 fathoms, became hard and stony, and retained this cha- 

 racter even after it had sloped about fifty fathoms down towards 

 the deep sea lying beyond. That there was here a pretty abrupt 

 descent is clear from the circumstance that we already at the 

 next station reached far down into the cold area with a 

 depth of 412 fathoms, and a bottom temperature of -f- i°'3 C. 

 Farther north, about the latitude of Trondhjem, we found 

 at a depth of 190 fathoms, and likewise on the boundary 

 line between the warm and cold area, a very similar edge with 

 rocky bottom, which falls off with a pretty steep slope towards 

 the west (Station 89 ^). Also on the opposite side of the tract of 

 s?a we traversed, we had occasion to observe a similar state of 

 things. Off the Fseroe Island.=, and at a considerable distance 

 from them, we were fortunate enough, though the weather was 

 exceedingly unfavourable, to find the outer edge or opposite 

 point of the extensive Fseroe bank (Station 38*), whereby its 

 extent and configuration could be to some extent determined, 

 and the state of things here appears to be very similar to the 

 Storegg. 



By the carefully-planned soundings which were undertaken 

 irom Ramsen Fiord westwards, there could be established at a 

 comparatively inconsiderable distance from the coast, the exist- 

 ence of a hitherto quite unknown, well-defined, steep bank of 

 considerable extent, with a hard bottom, and a depth of only 

 62-93 fathoms (Stations 63,^ 64,^ 65^). IBeyond this there was a 

 very gentle and even descent towards the great deeps, but we did 

 not here meet with any true edge as at the Storegg. It may be 

 added that in the outer part of Sogne Fiord (Sognfjoeen), we 

 found a pretty extensive plateau, with a hard stony bottom, and a 

 slope both inwards and outwards (depth from 206 to 21 1 fathoms). 



That all the points mentioned above are excellent fishing- 

 grounds I have not a moment's doubt. Everywhere, where at a 

 considerable distance from the coast, such banks with hard or 

 stony bottom have been found, there have always on closer exa- 

 mination been found large quantities of fish, and although an 

 attempt made by us by attaching to the lead a short line with 

 hooks and bait was unsuccessful, there cannot be any negative 

 conclusion drawn from this method of research, which was un- 

 fortunately, by reason of circumstances, very unsuitable for the 

 purpose. 



The kinds offish which are found on the sea-banks are, as is 

 well known, principally ling, torsk {Brosmus vulgaris), halibut, 

 and cod, the so-called bank cod. I have already, in, my reports 

 to the department, clearly set it forth as my opinion that the 

 so-called bank cod is not a different variety from the well-known 

 winter cod, or skreid, which in winter and all through the spring, 

 visits our coast for the purpose of spawning. The earlier hypo- 

 theses concerning the migrations of the winter cod {skreid) from 

 great distances in the sea, I have, after a close study of the nature 

 of this fish, been obliged entirely to abandon, and the experience 

 obtained during our expedition confirms me in this. It is my 

 conviction that the winter cod, which is to be found along our 



' Station 16, lat. 62° 23' 9" ; long. 2° 17' E. from Greenwich. 



* Station 17, lat. 62° 33'; long. 2" 4' E. from Greenwich. 



3 Station £9, lat. 64° 1' ; long. 6° 7' 5" E. (rem Greenwich. 



* Station 38, lat. 62° 57' : long. 3° 47 'W. from Greenwich. 



5 S ation 63, 64° 41' 3'' N. L., 9 E. from Greenwich. 



6 Station 64, 64° 42' N. L , 8'^50'E. trom Greeuwicb. 



7 Station 65, 64° 42' 5" N.L., 8° 39' E. from Greenw.ch, 



coasts during winter, and which is the object of some of our 

 most important fisheries, is during the rest of the year distributed 

 only over that tract of sea whose bottom forms the barrier 

 against the polar sea-deeps lying beyond it, and that the outer 

 boundary of this barrier (the so-called Havbro), with its well- 

 developed animal life and favourable bottom, forms a suitable 

 habitat for innumerable multitudes of this fish. 



Very dissimilar are the circumstances with reference to the 

 second of the varieties of fish most important for our fisheries — 

 the herring. Here my earlier researches have led me just to the 

 opposite conclusion. While the cod is evidently a genuine 

 bottom fish, and as such dependent on the nature of the bottom 

 and partly on the depth, the herring, on the contrary, in conse- 

 quence of its whole nature, is a genuine pelagian fish, and its 

 occurrence ii therefore exceedingly independent of the depth or 

 the nature of the bottom, but, on the contrary, deptndent on the 

 physical and biological conditions in the upper stratum of the 

 sea. As these are very changeable, this species of fish may have 

 been furnished with means to enable it speedily to seek out the 

 most favourable tract of sea. The herring has also, as contrasted 

 with the cod, obtained its elegantly-compressed, wedge-like 

 form, whereby with the speed of an arrow it can shoot along 

 through the water, and in a comparatively short time traverse 

 long distances. Although I do not adopt the old ideas, according 

 to which the spring herring comes as it were from theice-covtred 

 sea about the North Pole, I am, however, inclined to believe 

 that, not only when it visits the coast to spawn, but also during 

 the rest of the year, it undertakes irregular migrations in the open 

 sea. The distribution of the herring in the sea is dependent on 

 the distribution of the small animals which form its food. 

 These small animals are all pelagian, mainly small Crustacea of 

 the order Copepoda, which keep more or less near the surface 

 of the sea, and are commonly- known by our fishermen 

 under the name of " aat." Only when the herring during 

 win'er resorts to the coast to deposit its spawn are its move- 

 ments for the time independent of the occurrence of "aat." The 

 whole other part of the year, on the contrary, the shoals range 

 through the open sea, inasmuch as they prefer to betake them- 

 selves to that region of the sea where, at various seasons, there 

 is the greatest abundance of " aat." The great mass of the 

 herring shoals can thus very naturally, towards the approach of 

 winter, or at the time when the development of the organs of 

 generation drives them to resort to the coast in order to spawn, 

 be found sometimes at a less, sometimes at a greater distance 

 from their spawning places according as the sea in one direction 

 or another has the greatest abundance in " aat." On this again 

 mainly depends, I am convinced, the fluctuations in our spring 

 herring fisheries. For as the spawning migratioa leg'ns lung 

 before the roe or milt are ready to be deposited, the mass cf 

 herring, if at that point of time it finds itself close to the coast, 

 will reach it so early that it will be obliged to remain thtre for a 

 considerable time, during which it will naturally come to seek 

 closer in towards the coa;t in the fiords and bays. In the con- 

 trary case, when the mass o( herring at this point of time finds 

 itself at a considerable distance from its spawning places, so 

 longtime will have passed be:ore it reaches them that the spawn- 

 ing process will go on immediately aftef thtirarrival at the coast. 

 The herring will then remain only a short tin e along the coa&tj 

 and the spawning will then for the most part be carried on on 

 the outermost banks, less accessible to the fishermen, in othtr 

 words, the spring herring fishery will be very short or exceedingly 

 unsuccessful. 



This is, in short, the theory which I a1reidy_ several years 

 ago, in consequence' of researches made by me along our coasts, 

 was led to advance as in my view the only probable scientific 

 explanation of the remarkable irregularities which in course of 

 time are observable in our spring herring fisheries. I have, 

 however, unfortunately this time only very few facts to support 

 my theory with, and I cannot, therefore, be surprised if it has 

 been received with mistrust as merely a hypothesis. There are, 

 indeed, a few reports from seamen of their having observed 

 large herring shoals far out in the open sea, immediately before 

 the beginning of the spring herring fishing, as there have been 

 observed by others at various seasons of the year great masses of 

 " aat " at different points in the sea, and'we have information 

 concerning this last phenomenon, partly also from trustworthy 

 scientific men (Kroeyer), and that just from that region of the 

 sea, which here most interests us ; but these statements were, 

 however, too few to form complete evidence that the open sea is 

 in fact a suitable dwelling-place for the.enormous masses of herring 

 which at certain seasons of the year move towards the coast. 



I 



