_ 17 _ APPENDIX E: HEINCKB 



greatest interest to learn, whether such plaice of the 0-group occur frequently and regu- 

 larly on this south-west patch of the Dogger Bank, the shallowest part of the open 

 North Sea. 



The still older plaice of the 0-group , of over 50 mm. in length, have been fished in 

 very large quantities in late summer and autumn, but with few exceptions, always within 

 the 20 m. line and here almost constantly in the neighbourhood of the land, especially, on 

 the shallow sands of the Elbe and Weser estuaries in the "Wattenmeer" and imme- 

 diately off the shallows of the German coast. The 0-group occurs here, without exception 

 with the I-group. Both groups considerably overlap as to size. Towards the 

 end of their first year, i. e. in December, the young plaice reach an average length of 

 about 7 to 8 cm., from 9 to 10 cm. as a maximum, according to our observations in the 

 German Bight of the North Sea. We have, unfortunately, not made any extended obser- 

 vations as yet, regarding their habitat in winter. 



The plaice of the second year, therefore of the I-group, which have lived 

 a complete year, reach an average length of 13 to 16 cm. in the German Bight of the 

 North Sea, from 18 to 20 cm. as a maximum. These also, we have only taken — with 

 very few exceptions — within the 20 m. line, where, with the plaice of the third year 

 (Il-group), they form the great mass of the so-called under-sized plaice on the young- 

 fish grounds. The richest of these young-plaice grounds lie off the islands of Amrum 

 and Sylt in the north, off the mouths of the Elbe and Weser in the centre, and off 

 the islands of Juist, Borkum, Ameland and Terschelling in the west. 



The third year's group of the plaice just mentioned (Il-group), reach an average 

 size of 18 to 20 cm., about 25 to 28 as a maximum. We have found it in great quanti- 

 ties within the 20 m. line, outside this line also, though in smaller quantities, as far as the 

 40 m. line, but beyond the latter line only very exceptionally. 



It is the fourth year's group of plaice (Ill-group), with an average length of 25 

 to 27 cm., which is first caught in quantities worth mentioning in the open North Sea 

 beyond the 40 m. line, although it has also been met with in greatest numbers within 

 that line. 



These discoveries — which, it must be remenbered, are limited to the period March 

 to October — have shown without exception the noteworthy fact, that the occurrence 

 of the young plaice, from the coast to the open sea, is arranged like the 

 steps of a ladder as regards the increase in size; the smallest and youngest 

 occur quite close to the land, the largest and oldest the furthest out. 



The curves added here (Fig. 2) give the percentages of 7 hauls of plaice made by us 

 on the 23''ä and 24^^ July 1903, on a ground to the north-west of the island of Juist as 

 far as the 40 m. line: 5 hauls with the 90-foot trawl and 2 with the Heligoland young- 

 fish trawl. We see (1), that the number of plaice caught increases as we pass from the 

 open sea towards the coast, (the number 1561 of the haul made close to the land with the 

 Heligoland trawl, should be multiplied several times for a true comparison, as this haul 

 lasted only 35 minutes, whilst those with the large trawl were always much longer, from 

 2 to 4 hours); (2) that the average size of the plaice steadily decreased from the sea 

 towards the land, from about 24 cm. to 9 cm. The two parallel hauls with the large and 

 the small trawl (V and Va) at the same place, are worthy of remark; they show very 

 clearly, that the hauls with the large trawl do not take all the size-groups present, and 



Appendix K ^ 



