— 155 — JOBS. SCHMJDT 



The outer coiidilioiis (eapocially toniperaluio) also inlluonce the time of 

 spawning. 



It is not only the spawning region but also to a certain extent the spawning time 

 which is dependent upon the hydrographical conditions. It may be said in general that 

 almost all our gadoids spawn in the spring, but this statement re quires further 

 definition; in the iirst place, the species differ in that some have a longer spaAvning time 

 than others and in the second place, the spawning of one and the same species is not 

 everywhere at the same time within its spawning regions. The rule is in general that 

 spawning is earliest in the southern, latest in the northern parts of the 

 spawning regions. Examples of this are given in the Special Part for almost all the 

 species; compare for example the spawning of the haddock in March— April on the British 

 Atlantic coasts and in May— June at N. W. Iceland, the spawning of Gadus Poutassou in 

 the Bay of Biscay and south of Iceland', and the spring and winter spawning of the hake 

 in the Bay of Biscay (and Mediterranean) with its summer spawning on the north of 

 Scotland and in the Skager Kak. 



It is naturally not the situation of a locality , whether to the south or north , which 

 by itself determines the spawning time of a species, but rather the hydrographical condi- 

 tions^. That the spawning near the northern boundary of the region is in general later 

 than near the southern is rather an expression of the fact, that the temperature in the 

 former localities is later in reaching the favourable height for the spawning of the species 

 than further south. This appears very distinctly in the "after-spawning", which in species 

 with prolonged spawning may take place in waters far removed from the main spawning 

 region, whether to the north or east (cf. the "after-spawning" of the cod (and lemon dab) 

 at North Iceland in the summer time and the late spawning of the poor cod and pollack 

 in the North Sea and Skager Rak, described pp. 49 and 74). 



From this standpoint, that there is a close connection not only between the spawn- 

 ing region and the hydrographical condition but also. between the latter and the spawning 

 time , it is of interest to compare not the spawning time of the separate species but the 

 spawning times of the two hydrographic-biological groups: the "northern" and "southern". 

 To the former belong the species which spawn at Iceland, to the latter those which spawn 

 in the Bay of Biscay and the Channel, and it will be remembered that the British Isles 

 and the North Sea were common to both groups or a "meeting-place". If we now examine 

 into the conditions here where the spawning regions of the two groups meet, we find that 

 the "northern" group spawns on the whole early, the "southern" group 

 late, which appears to be in good agreement with the fact that the latter group re- 

 quires higher temperatures than the former. 



Mode of life of the early stages; the pelagic stages and the bottom 

 tages; the varying duration of the former in different species and in 

 different waters. 



It holds good for all our species that the fry in the beginning lead a pelagic life, 



' At the end of Blay the fry taken south of Iceland were quite small (under 1 cm. long), at the 

 begiimiiig of May those found in the Bay of Biscay were mostly over 5 cm. long. 



'^ Compare with this the conditions described on p. 127—28, that in agreement with the hydrographical 

 conditions there is a greater difference between S. Iceland and E. Iceland than between S. Iceland and 

 S. Ireland with regard to the gadoid species spawning there. 



20* 



