APPENDIX K: KYLE _ 56 _ 



D. SUMMARY AND CONCLUSIONS 



The main conclusions arrived at during the progress of this work may be briefly 

 summarised. 



The preliminary discussion showed the advisability of regarding overfishing as mainly 

 a practical question. The chief problems for scientific consideration — the 

 theoretical aspect of overfishing — are centered round the possibility of man's 

 influence effecting some change in the composition of the existing stock 

 of a species or even causing a decrease in the quantities of the species 

 These are, therefore, the points to be investigated from the statistics (p. 4). 



A discussion of the plaice fisheries of the north-west coast of Norway and of the 

 plaice fishery of the Kattegat, has shown the effects of severe fishing. In the first case, 

 the plaice of large size were fished up within a few years and the fishing ceased. In the 

 second case, the plaice of large size have also been fished up, but the fishing has remained 

 practically as it always was, though the intensity of the fishing has greatly increased. 



These phenomena are explained by reference to the physical conditions. The plaice 

 live in moderate depths, mostly from the shore to 40 fathoms, becoming rare at 60 and 

 65 fathoms. On the exposed Norwegian coast, the areas adapted to the plaice are very 

 circumscribed in extent, and the currents prevailing there are strongly against the young 

 stages of the plaice reaching a spot favourable to their development. The consequence 

 is, that the suitable areas on the Norwegian coast receive but small contributions of 

 young plaice each year, and it takes several years for a sufficient number to collect to 

 permit of a remunerative fishery. The fishery is thus based on an "accumulated 

 stock" of plaice. When this stock has been reduced by man, the quantities present 

 of the middle-sized smaller plaice, are not sufficient to support a remunerative fishery (p. 6). 



The physical conditions of the Kattegat, on the other hand, are specially suited to 

 the plaice. The pelagic young are not carried away from the area by the oceanic cur- 

 rents, and have a large tract of warm sandy flats on which they can and do grow in 

 abundance. The removal of the "accumulated stock" of large plaice by man has not 

 appreciably affected the fishery. The statistics show, that the total quantities taken annu- 

 ally have remained practically about the same level for a long period of years, subject 

 of course to fluctuations which can be explained by changes in the physical conditions. 

 The persistence of the fishery after the "accumulated stock" had dis- 

 appeared, has led to the conception of the "current stock", that is, a secon- 

 dary supply, which is approximately equivalent to the "accumulated stock" 

 in quantity or weight, and thus maintains the fishery, but contains greater 

 numbers of a smaller average size. The proofs for the existence of this "current 

 stock" are based partly on the above-mentioned results of the examination of the statist- 

 ical data, partly on the results of plaice-marking experiments. It has been shown, that 

 the young plaice grow faster on grounds where they are relatively less abundant than 

 on grounds where they are more abundant. The removal of the larger plaice of the 

 "accumulated stock", and also the strenuous fishing, leave more room and food so that 

 the young can now grow faster than formerly (p. 20). 



In discussing the Kattegat plaice fishery also, it has been pointed out, that the mode 



