APPENDIX E: HEINCKB — 6 — 



in the free water over the bottom of the sea. Not ouly are quite other kinds of fishing 

 apparatus required here than for the eggs and larvse, but these new apparatus for young fish 

 must also be of many different kinds and satisfy specially strict conditions, if they are to 

 display the actual facts in any way exactly. In order, for example, to be able to deter- 

 mine for certain, if the first, youngest stages of the plaice and dab (PI. limanda) occur at 

 a certain part of the bottom of the sea or not , we must employ a net with sufficient 

 stretch to cover a large area, with a ground rope sufficiently sharp to bite into the ground 

 and lastly with a mesh in the bag as small as possible, in order that small flatfish of 10 — 

 12 mm. in length can be caught in it. With such apparatus, we must fish at the most 

 different depths, from close to the shore to 100 m. and more, and sometimes slowly, some- 

 times fast; the latter especially, if we wish to take young gadoids like the cod and had- 

 dock, as well as flat-fish. 



Again, other apparatus are necessary for the sure capture of the larger, active fish- 

 larvse, e. g. herring-larvse, and young gadoids of 3 — 10 cm. and over, which swim in the 

 free waters of the upper and middle layers. They must have, especially, as wide a mouth 

 as possible in order to be able to fish through a relatively large section of water; they 

 must — at least at the hinder end — have sufficiently small meshes, and they must finally, 

 also be strong and resisting and permit so much water to pass through, that they can 

 be towed according to requirements with a moderately great velocity — several nautical 

 miles per hour — without tearing or otherwise hindering their fishing-capacity. They must, 

 lastly, be usable at different depths. 



All these conditions, again, cannot be fulfilled by a single kind of net alone; several 

 different nets are constantly to be used at the same time, in order to be able to determine 

 the true state of things. If only one kind of net is used, quite a false result may be 

 obtained, e. g. the absence of a certain species, which really occurs in abundance. 



The experience, that very different and specially constructed apparatus 

 are necessary, and that several of them must constantly be used at the 

 same time, in order to determine for certain the occurrence of the eggs, 

 larvse and later young stages of the food-fishes, is one of the principal 

 results of our investigations in this field. This experience holds also, however, 

 for a much larger field in the investigation of the occurrence and distribution of the food- 

 fishes, namely, for the capture of larger and the largest fishes. It may be considered cer- 

 tain, that the practice of the sea fishery has no single net which takes all fish dwelling 

 on the spots fished. Even more, there is not a single net which, even if it catches only 

 a portion of the fish present of a species, e. g. the plaice, brings up a true, at least 

 a natural, representation of the various sizes on the ground. The large Otter trawl ordi- 

 narily used in the deep-sea fishery of the North Sea, with about 90 foot head-line (com- 

 mercial trawl), catches, for example, the small plaice under 12 cm. not at all or only in 

 relatively very small quantity; they escape through the meshes. This same net, further, 

 catches more fiat-fish or more round fish, according to the nature of the ground rope and 

 according to the rapidity of sailing during fishing. Smaller ground nets with smaller 

 meshes, on the other hand, bring up naturally the small plaice under 12 cm., but of the 

 larger kinds, they obviously take relatively much too few. 



Lastly, it must still be mentioned that there is, for large areas of the bottom of the 

 North Sea — namely, all those with more or less stony rough ground — still no apparatus 



