— 29 — APPENDIX B: HEINCKE 



Elbe, in the Clay Deep at the south corner of the Dogger, and in the deep water of the 

 north-west corner ot this bank, as well as on the eastern parts of the Oyster Bank etc. 



The temperature and salinity of the water, where these small cod were taken, varied 

 from 6° C. and 35 "/oo salinity in the region of the Great Fisher Bank, and beyond the 

 100 m. line in depths of 70 to 134 m., up to 20° C. in the shallower coastal waters of the 

 southern North Sea at 10 m. depths, and down to salinities of 31-30 and less pro mille in 

 the mouth of the Elbe. 



The places, where we obtained most cod of the 0-group in June und July, agree in 

 general with those spots, where most eggs and larvae had been fished previously. Never- 

 theless, it is indisputable, that, as the eggs and larvas were not found in the immediate 

 neighbourhood of the coast, the young fry must have spread out from the regions, where 

 they were born and thus succeeded also in coming close into the land. 



It is remarkable, that we caught practically no young cod in our hauls with 

 the surface nets (Hjort's net, three-otterboards net), which brought us numerous other 

 young fish of the year. We obtained some few specimens, of 3 to 5 cm. in length, but 

 three times with these nets, namely, once respectively on the Fladen Ground, at Horns 

 Reef and on the east edge of the Dogger Bank, in the middle of July. It seems, there- 

 fore, as if the pelagic life of the young cod in the North Sea ceased soon after the com- 

 pletion of the metamorphosis, and that, when they have once changed over to the life on 

 the bottom, they rise again but rarely into the upper water-layers. 



The further fate of the 0-group has been investigated by us on the German coast and 

 at Heligoland. Whilst we found them in June mostly 3 to 5 cm., at the highest 8 cm. 

 long, in July mostly 4 to 6 cm., at the highest 11 cm., in August some were already 12 cm. 

 and in September 13 cm. At the beginning of October the most of the young cod on the 

 coasts of the mouth of the Elbe were 10 to 15 cm. long, the smallest but 7, the largest 

 18 cm. We found them at Heligoland to be from 6 to 18 cm. in length in October and from 

 12 to 20 cm. in November. It may reasonably be doubted, whether all these small cod belong 

 still to the 0-group, and not — at least some — to the I-group, and this can only be 

 solved by close investigation of the age on the otoliths and bones. We have already made 

 such determinations, but not yet in sufficient number as the cod is a very difficult subject 

 in this regard. We may, however, believe, e. g. that a small cod of 17 cm. in November 

 certainly belongs to the O-gi'oup, another of 20 cm. on the other hand already to the 

 I-group. We have reasons for believing, that the small cod at Heligoland are on an 

 average about 14 cm. at the end of their first year, 18 cm. perhaps at a maximum and 8 

 to 10 cm. at a minimum. Cod of the 0-group kept in our aquarium grow very quickly 

 in the summer and autumn, especially with good feeding, e. g. from the beginning of 

 August to the middle of September not less than 1 mm. daily on an average, from thé 

 middle of September to the end of October, still V2 to Va mm. daily; in the middle of 

 November we had cod of the 0-group in our aquarium up to 15-5 cm. In the open sea, 

 the growth would certainly be greater. 



Shortly before closing this report, we were able to make some further hauls with the 

 young-fish trawl on different stations of the seasonal cruises, from the 14"' to 23"' of 

 November, and in some of them we captured the cod of the 0-group. In the deep sea 

 north of the Dogger (69 m., Stat. Ill), these measured 6 to 13 cm., at St. XI (southern 

 slope of the Skager Kak) 7— 9 cm., at Stat. XV (off Sylt, 25 m.) 6 to 18 cm.; the two largest 



