viii INTRODUCTION. 



1907, which enabled me to obtain material sufficient to demonstrate that 

 very important results might be obtained by collecting material on a larger 

 scale, and more fully investigating the age and growth of the salmon stock 

 in Norway. 



In the autumn of 1907 I was requested by the Agricultural Department 

 to submit a scheme for such investigations, and, in accordance with my 

 proposals, the necessary funds have been annually placed at my disposal by 

 the Storthing. 



In order to obtain material for investigation which would fully represent 

 the salmon which are caught in our various fisheries in Norway, I selected 

 three different parts of the coast, namely the Christiansand district, the 

 Trondhjem district, and East Finmarken. Thanks to the courtesy of 

 Herr Tobias Tobiassen of Christiansand and of Messrs. M. Thams & Co., 

 Trondhjem, I have been able to collect examples of scales from the 

 different ice-houses during the salmon-fishing season, either from the whole 

 catch dealt with at the ice-houses, or from as many fish each day as it 

 was possible to arrange for. These gentlemen have also very kindly 

 allowed me access to their books, thus enabling me to obtain very 

 valuable statistics throwing light on the representative value of the samples 

 collected. I have further obtained from various other localities, partly 

 through the kindness of private individuals and partly thanks to the 

 assistance of fishery officials, samples of material throwing light on different 

 side-issues, and I have also collected during my travels considerable 

 numbers of samples of parr and smolts from the different rivers. 



With the progress of my studies on the salmon's age it became 

 increasingly evident that it was necessary and desirable to attempt at the 

 same time a careful investigation into the age and growth of the trout and 

 its many varieties. With this object in view I collected examples of trout 

 and sea-trout scales from a number of localities ranging from Finmarken to the 

 southernmost parts of Norway. Most of them I collected personally, though 

 many private individuals interested in the subject gave me valuable assistance. 



From abroad and especially from Great Britain, I received much 

 valuable help. Mr. Calderwood, the Fishery Inspector for Scotland, 

 rendered me assistance on several occasions, and Dr. Holt was kind enough 

 to send me over from Dublin a large sample of Irish salmon scales. Mr. J. 

 Arthur Hutton of Manchester also gave me invaluable assistance. His 

 splendid micro-photographs of salmon scales are already known from his 

 excellent papers on the subject, and he has now done me the favour of 

 placing his technical experience at my disposal, and has kindly executed all 

 the micro-photographs of scales from which the illustrations in this work 

 are taken. I am also largely indebted to this gentleman for arranging and 

 kindly supervising the English edition of the present paper. 



