60 



As is shown by tliis list the herring may be seen in the larva- 

 stage in the Zuiderzee nearly during two months (from May 23 

 until July 18); that larvae would have been also there before 

 May 23 might be coneluded from the circumstance that a good 

 many of those caught on that day had a length of 18 — 21 m.m. 

 already. I dare not estimate how much sooner they might make 

 their appearance in a year, when spring is early, but I feel sure 

 that also in this regard considerable diflferences may occur. 



The places where the larvae have been observed are also 

 mentioned on this list: they are all near the coast , and most 

 of them are situated in the eastern and south-eastern parts of 

 the Zuiderzee. There also the smallest larvae were taken, and there 

 the salinity of the water is smallest. At the first four stations 

 where larvae were taken the areometer showed even a remarkable 

 low degree of salinity: however , herring-larvae were caught also 

 in water with a somewhat higher percentage of salt , as was to 

 be foreseen from the fact mentioned p. 57 that herring-spawn was 

 met with also at such places as for example near Marken 

 and ürk. Those parts of the Zuiderzee which surrouiid the mouth 

 of the IJsel, being the least salt ones of the Zuiderzee, seem to 

 be highly favorable to the spawning of this fish. 



The greatest salinity recorded at a place in the Zuiderzee where 

 herring-spawn or herring-larvae were observed was 1.0087. This 

 eorresponds about with P/j, salt, whereas the Northsea contains 

 upwards of 3"/^ salt. Hofifmaun succeeded in hatchiug the eggs 

 of the Zuiderzee-herring in water containing also about P/^ salt, 

 and Meyer ^) says that in that part of the Baltic , where the 

 spring-herring spawns, the salinity of the water varies not incon- 

 siderably; (0.09- 0.54o/o in the mouth of the Schlei, and 0.9 — LSo/^ 

 in the western Baltic) ; yet it is always a good deal lower than 

 that of the Great Belt and other parts of the eastern Baltic, 

 where the winter-herring spawns , and where it is at least 2°/^^. 



1) Meyer, H. A., Beobachtungen über den Wachsthuin des Herings im westJichen 

 Theile der üstsee. Jahresber. d. Comm. z. wiss. Unters. d. Ueutschen Meere. IV — VI. 

 T878. S. 227-251. 



