— 152 — 



example of this, though we might just as readily choose any of the other "northern" species. 

 The northern boundary for the spawning of the haddock lies at the N. W. and S. E. of 

 Iceland, the southern boundary to the S. of Ireland. In spite of this however the had- 

 dock occurs in great quantities both in the young and older stages on the N. and E. of 

 Iceland; thus large masses of the pelagic fry are each year carried to these coasts from 

 the spawning places on the S. and W. coasts by the anticyclonic movement of the waters 

 which occurs round this island. On the other hand, although the southern boundary of 

 the spawning lies south of Ireland, yet not quite inconsiderable quantities of haddock may 

 occur in the Bay of Biscay according to Moread (see p. 57), especially in the northern 

 part but even though very rarely in the southernmost part. As will be mentioned in dis- 

 cussing the direction of the current in the Bay of Biscay (p. 162), I believe that the oc- 

 currence here of the haddock may be explained by a drift of the pelagic fry from the 

 waters S. W. and S. of Ireland, where we found no small quantities of the older pelagic 

 stages out over great oceanic depths (see Chart III), but however this may be, we see 

 that the haddock is distributed much further to the south than the spawning regions reach. 



On p. 142 it has been shown that the lowest and highest temperatures under which 

 the spawning of the haddock takes place are ca. 5'/2°— 6° and ca. 9° — 10°, a range of 

 ca. 4°. But if we examine into the lowest and highest temperatures under which the had- 

 dock occurs at all within the regions investigated (cf. Chart, fig. 11 p. 1H7), we find that 

 these are ca. 1° and ca. 12°, thus with a range of least 11°, which is much greater than the 

 range for the spawning. In this greater range we have an expression of the 

 fact, that the spawning region of a species is often much more restricted 

 than its distribution in general, and if we examine into the matter for all the other 

 species we find that this rule has general applicability. 



The above examples have been intended to show that the regions over which the 

 spawning fish occur are much smaller in extent than the whole distribution of a species, 

 and it has been shown that this is specially due to the more definite and restricted re- 

 quirements as regards the temperature during the spawning time. It is not only with 

 regard to temperature however, that the requirements of the species are more definite 

 during the spawning time, but also with regard to other outer conditions such as sal- 

 inity and depth. The coalfish {G.virens) and cod {G.cullarias) may be mentioned as 

 examples here. The former spawns not at all or extremely little in waters of less salinity 

 than ca. 35-10 — 15 "/oo or of less depth than 100 meters. In consequence of this and 

 because also the range of temperature is very small (ca. 6°— ca. 9° — 10°), the spawning 

 region is relatively much restricted in extent. Thus it is excluded from spawning in the 

 greater parts of the Channel (depth not sufficiently great) and the Skager Kak with the 

 northern part of the Kattegat (salinity too low). During the other stages of its life the 

 coalfish is however much less sensitive towards the salinity and depth ; for example , we 

 find the young coalfish in large quantities in quite shallow water right on the shore, and 

 even at the head of long, narrow bays where the depth is only 1 meter and the salinity 

 sinks to 20^/00 or even less^ In the Skager Rak and the Northern Kattegat, where the 

 salinity is too low for the spawning coalfish the young adolescent specimens may be found 

 in no small quantities. Thus there may occasionally be a fishery after the small coalfish 



' See the hauls p. 40 at the head of the long, narrow Funding Fjord in the Pseroes, where a hanl 

 with a small seine over 10 fathoms from Vh meters to land brought up 2127 small coalfish. 



