— 15 — APPENDIX E: HBINCKE 



the number of the otolith-rings agrees with the number of rings on the vertebrae in one 

 and the same fish. 



The extension of the age-investigations from the otoliths to other parts of the bony 

 skeleton of fishes, gives an essentially wider and more certain basis than hitherto, for the 

 determination of the age. The information they give, render it possible above all, to detect 

 and to distinguish also the age of the older and the oldest stages of the food-fishes. For 

 example, the annual rings on the bones of the gill-cover enable one to detect with 

 certainty, that large plaice from 60 to 70 cm. in length are 20 years old and more, and 

 that, from the 8*'' year onwards, the yearly growth in length is small in comparison with 

 the earlier rate of growth and decreases more from year to year. A turbot of 19 pounds 

 weight (21 lbs. English) is at least 11 years old, a large cod of 100 to 120 cm. 9 to 11 

 years. Large Norwegian herring of about 300 to 350 cm. in length are 6 to 8 years old. 



C. statement of the results 



It may be explained in the beginning, that special cruises for the investigation of the 

 eggs and larvae of the food-fishes, were only made by our research-steamer "Poseidon" during 

 March 1903 and 1904, in July 1903 and in June 1904. On the other hand, in the 

 important spawning months of January and February, either no hauls at all could be 

 made or only in February during the hydrographical seasonal cruises, and then, only quali- 

 tative hauls for the most part. During 1902, 1903 and 1904, eggs and larvae were also 

 sought for during the May seasonal cruises, mostly qualitatively, more rarely also quanti- 

 tatively. Cruises with the Poseidon for fishery investigations, for the young and larger 

 fish, were also made in October and November 1902, in March, July and September 1903 

 and in January, March, June and July 1904. It must also be specially mentioned here, 

 that everywhere, where a series of hauls of all kinds was made, the temperature and 

 salinity were also determined. 



1. The plaice [Pleuronectes platessa) 



Eggs and larvae. Plaice eggs were fished by us during the March cruises in such 

 small quantities, that we must believe that the spawning period of the plaice was practi- 

 cally over by this month. A further sign of this was, that just as many larvae (74) as 

 eggs, were taken altogether (all the vertical hauls taken together). 



The largest quantity of eggs and larvae was taken on the 6"i of March 1903, N.W. 

 from Heligoland near the 40 m. line (German Station I), namely, about 32 per square 

 meter of surface; almost as large a number was met with close to this spot, both to the 

 north (Sylt outer ground) and to the south (N. from Terschelling), but only on the 40 m. 

 line. Smaller quantities were also found nearer to the land, about the 20 m. line, both in 

 the southern and northern parts (to 56° N. L.) of the region sailed through. In the open 

 North Sea (Great Fisher Bank, Dogger Bank), plaice eggs were often met with singly but 



