APPENDIX K: KYLE _:_ 22 — 



and Dahl in the Norwegian plaice fisheries; it marks the decrease and even disappearance 

 of the "accumulated stock". 



The continuation of the fishery since l8go, at its maximum intensity and high produc- 

 tivity, can only have been possible because the young plaice annually grew sufficiently 

 rapidly and in sufficient numbers to replace the quantity (mass or weight) of the larger 

 plaice, which previously had formed the basis of the fishery. This so to speak second 

 supply of plaice, which maintains the fishery after the disappearence of the accumulated 

 stock has been called the "current stock". It is well represented in a diagram contained 

 in the Danish Report for igoo (Plan III, p. 86), and as this diagram may be taken to 

 represent the actual condition of the fishery, it is worthy of reproduction here (see p. 21). 



The line AS is drawn to represent "the original or accumulated" stock of plaice, 

 the dark lines are the "current stock". 



It will be remarked, that the general course of the curves agrees well with that drawn 

 by Petersen' for the imaginary species "P" and called by him III b. To a certain 

 extent also, the line AS drawn here corresponds to his curve III a, representing the accu- 

 mulated or "orginal stock of all P." Petersen, however, makes his III a group include 

 III b, whereas the line AS, representing here the "accumulated stock", cuts across the 

 lines of the "current stock". 



This difference represents an important difference in view. Petersen has drawn 

 his curves on the assumption, that "statistics prove that the weight of "P" (his "hypothet- 

 ical species") annually is not at present so great as formerly". The present curves are 

 based on the data just shown with regard to the plaice fishery of the Kattegat. If the 

 line AS were drawn, as Petersen has it, to include all the other curves, this would 

 clearly be opposed to the conclusion the statistics show, namely, that the quantity of 

 plaice taken annually from the Kattegat has not decreased over the period of years, for 

 which statistics exist. 



This explanation of the persistence of the Kattegat plaice fishery is, in the light of 

 known facts, more than a mere supposition. If the quantities of the largest plaice have 

 decreased, the quantities of the smaller and medium-sized must have increased, in order 

 to maintain the total quantities taken annually at the same constant level. This is a 

 conclusion which, in slightly different forms, has already been put forward by other ob- 

 servers. Thus, Mc Intosh and Masterman, in their work on "British Marine Food- 

 Fishes" (pp. 99, 100) point out, that one effect of "overfishing a district, will be that of 

 multiplying the numbers", meaning thereby, that the removal of the large fish gives 

 more room and sustenance to the smaller. The same idea has been expressed by 

 Petersen in the essay cited and we have further evidence from his observations that, 

 "in the region round Horns Reef, where the young plaice are very numerous, they grow 

 but slowly, from 4 to 5 cm. yearly, whereas further north in the Skager Rak, where the 

 number of plaice caught per hour is much less than at Horns Reef, they grow much 

 faster, ca. 8 to 11 cm. per annum" 2. 



Finally, it has to be noted, that the natural tendency of the Kattegat plaice fishery 

 to remain at a fairly constant level is aided by the mode and conditions of fishing. The 

 size of mesh used in the fishing apparatus is larger than that in the narrowest parts of 



■ "What is Over-fishing"; Jour. Mar. Biol. Ass., vol. VI, 1903. 

 2 Manuscript not yet published. 



