APPENDIX E: HBINCKE _ 30 — 



of these — 17 and 18 cm. — might belong to the I-group, whilst those of a complete 

 series from 6 to 15 cm. are certainly all of the first year. 



Cod of the 1-, II- and lll-groups. 



We estimate the average length of the I-group of cod of the southern North Sea at 

 20 to 25 cm. during their second summer, that of the Il-group in their third year at 

 about 35 to 40 cm. Both of these groups will naturally overlap considerably as to size, 

 just as with all fishes. With regard to the occurrence and distribution of these three 

 groups (of the second to the fourth year), it is a remarkable result of our hauls, that all 

 three groups of the young, immature cod are found everywhere intermixed 

 over the whole region under survey, and that there is no regular division 

 according to age and size. We have taken cod of 16 to 25 cm., of the I-group 

 therefore, both in depths over 100 m. on the Fladen Ground and in the Skager Rak, and 

 at the German coast and at Heligoland, also on the Great Fisher Bank, to the west and 

 east of the Dogger Bank, at Horns Reef and elsewhere — and the same holds good for 

 the other groups. At Heligoland, especially, all three groups are met with, both close to 

 the rocky ground on the island and further off the whole year through; the fish of 

 the 11- and Ill-group are relatively more abundant further out to sea, than those of the 

 I-group. The two former groups, therefore cod of about 30 to 50 cm. in length, are taken 

 in quantities with hand-lines from spring to late autumn. 



On account of our insufficient observations up to the present, we cannot yet state with 

 certainty, at what age, and at what size the cod spawn for the first time in the North 

 Sea, or in the southern North Sea in particular, chiefly because we have not yet had the 

 opportunity of catching large quantities of spawning cod, or cod approaching ripeness, or 

 even . those which had spawned. It is certain, that we have taken such cod in small 

 number from 60 cm. onwards in length, and it is probable, that some spawn for the first 

 time at 50 cm. or a little greater length. We learn from the bones, that a cod 50 cm. 

 long has lived at most 4 complete years, and we believe — provisionally — that the cod 

 does not spawn for the first time, until it has lived 4 complete years, prob- 

 ably at the end of its 5th, at latest the 6t^ year. We kept a female cod in our Heligoland 

 aquarium from September 1902 to June 1904; it spawned there in January 1904 (but not 

 in the previous year) and measured, in June, 66 cm. in length. Its age, according to the 

 vertébrée and bones, was 5V2 years. It had therefore spawned at the end of its 5* year 

 for the first time, but the sexual products had begun to ripen in autumn 1903, therefore 

 after the completion of the 4*^ and in the course of the 5* year. 



Our further investigations on the age permit us to take as tolerably certain, that a 

 North Sea cod of 75 cm. in length is at least 7 years old, one of 85 cm. at least 8, of 

 95 cm. in length about 9, and of 100 to 110 cm. in length at least 9 to 11 years old. 

 Certainly, the yearly increase of growth also decreases here after the beginning of maturity. 



Such large and older cod have been found within the region under our survey, mostly 

 far distant from land in the open North Sea in summer; in winter, however, especially on 

 our March cruises, they are also common near and on this side of the 20 m. line and often 

 quite close to the land, e. g. close to Heligoland, Horns Reef etc. It is known, that very 

 large and dense shoals of large cod, quite near spawning, occur on the trawling grounds to 

 the north and south of Horns Reef between the 20 and 40 m. line in winter, especially in 

 December, and give occasion to a very rich fishery. We have, unfortunately, not yet had 



