of the, Fishery Boo.rd for Scotland. 



51 



crease of these species was not in any way due to artificial proyjagation. 

 The conclusion, therefore, is that tlie increase in recent years in the num- 

 bers of these fishes brought to the market at Cbristiania has been brought 

 about by the action of a general cause or causes, whether natural or 

 economic, as increase in fishing. It does not of course follow that no 

 benefit as regards cod accrued from the liberation of cod fry, but any 

 benefit of the kind that may have been conferred cannot be separated 

 from the results due to the operation of the general cause, and the proof 

 therefore fails. 



7. Special Investigations. 



Two special investigations have been made to determine the effect of 

 the liberation of larval fishes on the abundance of the young of the same 

 species in the locality. One was made in Norway with reference to the 

 cod, and the other in Scotland with regard to the plaice. The Norwegian 

 investigation was carried on jointly by Mr. Dannevig, the Director of the 

 Hatchery at Flodevig, and by Mr. Knut Dahl, of the Fishery Depart- 

 ment. Certain fjords were selected in which the approximate abundance 

 of young cod of the year was ascertained by hauls with a seine, at the 

 same places and dates, both before and after fry of the cod from the 

 hatchery were introduced into the fjords in question.* The results are 

 shown as follows : — 



SoNDELEDFJORD, 



1903 

 1904 

 1905 



Cod Larvae 

 Liberated, 



None. 

 20,000,000 

 28,000,000 



Cod Fry 

 of Year 

 taken. 



426 

 1,523 

 1,133 



Average 

 per haul. 



4-8 

 15-1 

 11-5 



Hellefjoed. 



Cod Larvse 

 Liberated. 



None. 



None. 



8-9,000,000 



Cod Fry 

 of Year 

 taken. 



36 

 133 

 143 



Average 

 per haul. 



1-9 

 6-5 



7-5 



The>?e hauls of the seine were taken in each year at closely-corresponding 

 dates in September and October, but other hauls were also made in 1904 

 and 1905 in each fjord in July-August, with the following results : — In 

 Sondeledfjord the average number of cod fry of the year per haul was 

 33-7 in 1904 and 11-5 in 1905; in Hellefjord the average was iO-9 in 

 1904 and \b in 1905. Since fry were put in in both years in 

 Sondeledfjord, the only point to be noted is the diflference in the average 

 in the two years, but in Hellefjord no fry were put in in 1904, whereas 

 about eight or nine millions were added in 1905, when the average was 

 low. The two investigators, unfortunately, do not agree as to the 

 interpretation of the results of their investigations. Dannevig very 

 naturally comes to the conclusion that the increase in the number of cod 

 fry in the years in which cod larvae were added in the spring was due to 

 the addition of these to the fjord, and he gives the following summary of 

 the results, including the numbers of other young gadoids taken : — 



* Aarsheretniny vedkommende Norges Fiskf,rier for 1906, Isie ITefte : A sum- 

 marised account by Mr. Dannevig and by Mr. Dahl of their investigations is 

 given in the Report on the Lancashire Sea Fisheries Laboratory for 1906, 

 pp. 104, 109. 



