APPENDIX E: HEINCKE _ 32 _ 



a depth of 103 m. on the 12* of July 1904, and brought up over 1000 young fish in one 

 hour from 1 to 15 m. depth, consisting of about 900 whiting and 100 haddock, the latter 

 from 3 to 11 cm. in length; cod were quite absent. On the following day, further to the 

 east on the southern edge of the Skager Eak, in 184 m., we obtained not a single haddock 

 with the ground net, but 29 haddock of 3 to 10 cm. in length with the three-otter- 

 boards net. A haul with the Heligoland trawl on the Fladen Ground in 83 m. depth, on 

 the 9'*' of July, only brought up some few whiting; a haul with the three-otterboards net 

 at the same place, in about 1 to 30 m. depth, gave several hundreds of young fish, mostly 

 whiting, but also 17 haddock from 3 to 6 cm. in length. 



We may therefore conclude, that the young haddock of the North Sea retain the 

 pelagic habitat after the completion of the larval stage longer, and up to a greater length 

 (11 cm.) than the cod, or otherwise, comes up from the bottom into the upper water-layers 

 offener than the latter. It is similar in this to the whiting. 



The salinity of the water at those places of the North Sea, where we caught young 

 haddock of the 0-group with the ground-net, varied from 34-6 to 35-1 "/oo and the corre- 

 sponding temperatures from 6-5° to 7-1° C. On the other hand, the salinity and temper- 

 ature of the surface water-layers, in which we found the 0-group with our pelagic nets, 

 varied from 32-1 to 35-1 "/oo, and from 12-4° to 15-7° C. The low surface salinity of 320/oo 

 was found in the Skager Kak (Baltic stream), where 35 "/oo was found at the bottom. As 

 some haddock were also taken at the bottom here, though very few, we may conclude, 

 that the young haddock, from 3 to 10 cm. in length, may stand well a somewhat great and 

 sudden change in the salinity and temperature of the water. 



From lack of sufficient material, we cannot as yet say with certainty, what average 

 size the young haddock reach at the end of their first year. Similarly, our investigations 

 concerning the older stages of the haddock from the I-group to the spawning age, are also 

 very deficient, especially as regards the determination of the age from the otoliths and 

 bones. Nevertheless, we have some certain discoveries to show, and these allow some few, 

 but important conclusions concerning the biology of this fish. 



In July, 1904, we caught not only many haddock of the 0-group, but also large 

 quantities of the succeeding age-groups, in the north-western part of the North Sea on 

 the 100 m. line with our shrimp-trawl. These captures, which along with some smaller, we 

 were able to make in various parts of the northern North Sea in the middle of November of 

 this year, shortly before closing this report, gave some data regarding the relation between 

 the 0-group and the I-group. The accompanying curve (Pig. 4), gives a graphic represen- 

 tation of the size-relations of the 1836 haddock taken in these hauls. From the hauls 1 

 and II, which were made at the same place, but the one with the Heligoland young-fish 

 trawl, the other with the large trawl, we see at once, that the first net (I) with its small 

 meshes catches chiefiy the small and smallest fish from 3 to 10 cm., representing here the 

 0-group of the haddock, but the larger, belonging to the I-, II- and succeeding groups, in 

 smaller numbers. The large trawl (II) has taken no haddock under 14 cm., those from 

 15 to 21 cm. chiefly, also a goodly number from 24 to 32 cm. in length. 



We learn from this table the following: (1) The curve, giving the measurements of 

 all the haddock taken on the 10* of July, shows two deep and one shallower depression 

 and two high and two lower maxima. The deep minima lie at 11 and at 22 and 23 cm.; 

 they obviously separate the 0-group, with the maximum at 6 cm., from the I-group with 



