_ 25 — APPENDIX B: HEINCKB 



able, that we took the 0-group of the dab in almost every haul, but in none 

 in very great quantity (100 to 1000), as e. g. whiting, cod, Drepanopsetta etc. of 

 similar age, although we should expect this judging from the enormous number of eggs. 

 The largest quantity we caught, amounted to 57 and was taken in one of our hauls with 

 the Heligoland trawl, which usually lasted from 20 to 30 minutes, on the 21^* of July 

 1904 in 37m. on the northern portion of the southern Mud Bank. It is further remark- 

 able, that we have taken the youngest stages, the 0-group of the dab, extremely 

 seldom in quite shallow water immediately on the beach, as is the rule with 

 the plaice and also the flounder; almost without exception they were found in deeper 

 water. This great and striking difference between the occurrence of the plaice and flounder 

 on the one hand, and that of the dab on the other, as well as in the distribution of the 

 youngest bottom-stages, is shown also in the older stages. These stages of the dab are 

 distributed over the entire region investigated, intermingled with one another, and never in 

 such a graded distribution from the coast outwards as with the plaice. Young dabs of 

 6 cm. in length, were found at numerous places from the Great Fisher Bank southwards 

 as far as the beach at Heligoland, to the mouth of the Elbe and to the "Wattenmeer", in 

 common with others of 15 to 20 cm. and larger. At Heligoland, we have several times 

 caught, on previous occasions, thousands of dabs of the I- and Il-groups with one haul 

 of our small trawl in about 10 to 20 m. depth. Dabs of the most different sizes are so 

 regular in their appearance in the hauls with the large trawl, that we were once very 

 much astonished at not catching a single dab, either in our large or small trawls, at a 

 spot beyond the 100 m. line, 58° N. L. and 1° 10' E. L. in 134 m. It seems almost, as if 

 the limit of this, the commonest of the North Sea flat fishes, occurred here. In the Skager 

 Eak, we have taken dabs at even greater depths than 100 m. 



According to our observations, the dab becomes mature at a very small size, 

 in the Heligoland region, at any rate, from 16 cm. onwards. We have not yet made very 

 close investigations into the age of the dab. 



The picture which the biology of the dab in the North Sea offers us, is 

 essentially different from that of the plaice, as our observations show. The dab appears 

 to be distinctly a stationary fish, as the eggs, larvae and all the older stages of the adult are 

 distributed uniformly and beside one another over a wide area. A graded distribution of 

 the various age-groups, according to depth and distance from the coast, does not occur; 

 just as little is there a migration of the metamorphosing larvae from the sea to the coasts 

 in order to reach the bottom there — a phenomen so characteristic for the plaice and 

 flounder. 



4. The long-rougli dab (Drepanopsetta platessoides) 



Of the eggs and larvae of this species, 77 eggs and 8 larvae altogether were taken 

 in the vertical hauls of the March cruises of 1903. The height of the spawning was, how- 

 ever, not yet passed in March. The greatest numbers, 36 eggs and larvœ per square meter 

 of surface, were taken at the north edge of the Dogger Bank. Quantities of 12 to 20 

 per square meter were found on the Great Fisher Bank, and of 6 to 8 . in the neighbour- 

 hood of the Skaw. Further, small quantities were also taken on the outer Horns Reef 

 ground. In the south eastern portions of the North Sea, they were practically absent. 



On the May cruises Drepanopsetta-la,rvx were found regularly, especially to the north 

 of the Dogger Bank and in the vicinity of the Great Fisher Bank; they were mostly 



Appendix E ^ 



