642 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



their existence probably to some species of codflsli, to judge at least 

 from the time of the year when they are found.^^ 



Regarding the spawning-time of our Bohuslan coast herring it has 

 already been mentioned that it is in spring or from the middle of JMarch 

 till the middle of May, chiefly in April.^^ It must be supposed, how- 

 ever, that the larger herrings, especially on the northern coast, occasion- 

 ally spawn somewhat earlier, sometimes in February, whilst on the south- 

 ern coast the spawning season sometimes lasts till June.^^ Hydrological 

 conditions, especially the temperature of the water, exercise a consider- 

 able influence on the time when the spawning-season begins ; it gen- 

 erally begins earlier on the northern than on the southern coast, on the 

 outer than on the inner coast ; earlier also after a mild winter and par- 

 ticularly favorable weather. Cold and especially the formation of ice 

 seem to have a great influence on the time of the propagation of the 

 herring.^^ No race of herrings, as far as known, spawns about the time 

 of the winter solstice, but either so long before this period that the 

 young fish may grow to some size before the hardest winter weather 

 sets in, or so long after it that the newly-hatched fish soon meet with 

 mild weather, or are at least not exx)osed to the dangers consequent 

 upon the formation of ice. The herrings do therefore not spawn on the 

 coast of Scandinavia during December and the first half of January, 

 nor during the latter half of November.^^ It is probable that the spawn- 

 ing-season of a race of herrings has in course of time been fixed accord- 

 ing to the varying occurrences of the food required for the young fish, 

 which chiefly seems to consist of young mollusks and small crustaceans.^^ 

 The spawning-season of the herring in a given locality does doubtless 

 to some extent depend on the propagation of these small marine animals. 



As those herrings which spawn in March and April are generally 

 larger than those which spawn in May, these latter are probably her- 

 rings which spawn for the first time.^^ The three-year-old herring, which 



^^Verslmj van den Staat der NederlandscheZeevischerijeu over 1860, p. 29— Vitkomsten ver- 

 kregen uit de journalen der haring-schepen. Berigt bij het komnklijk Meteorologisch In- 

 stituut over 1860, p. 6-7. 



"When speaking of the " spawning-time" of a race of herrings, we always mean the 

 time when large numhers of fish are spawning ; and no one shouhl he led to consider 

 another season as the " spawning-time " hecanse hoth before and after that time some 

 herrings will spawn. 



isp. DuBB, " Anteckningar om sillfisket Bohuslan." Kgl. Vetensk. Acad. Handl. f. 

 ar 1817, pp. 35, 44. 



16 Compare Professor KrOyer's excellent remarks (Danmarks Fiske, III, p. 170) re- 

 garding the influence of the ice on the spawning-time of the herrings in the Baltic. 



I'See note 14, as also NiLSSON, "HandUngar rurande sillfisket," p. 56. Ekstrom, "Die 

 Fische in den Seheeren von Morko," p. 220, 223, and: " Jahresberichi der Commission zur 

 tvissenschuftUchen UntersucMng der deutschen Mee^-e." IV-VI., pp. 100, 237, 248, 249. 



^^Stockholmslans Egl. HusMllnings-Sdllskajys handlingar. VI, Stockholm, 1855, p. 197.— 

 BOECK, "Om Silden og Sildejiskerierne," p. 15. 



'9 The same opinion has already been advanced by A. W. Malm in " Goteborga och 

 ■Bohuslans Kgl. Rushallninga Sdllskapa handlingar," 1857, p. 21. 



