REPORT ON ''AGE AND GROWTH OF THE HERRING IN CANADIAN WATERS." 



I.— INTRODUCTION. 



Dr. Johau Hjort has requested me to ^work up the material of scale samples and 

 observations bearing on the biology of the herring, collected in Canadian waters 

 during the Dominion Government expedition, 1914 and 1915. The points especially 

 taken into consideration ,'when collecting the material — and which naturally also 

 furnish the main problems to be dealt with in the present work — have been formulated 

 by Dr. Hjort, in his preliminary report (VI) as follows: — 



1. Do the herring that visit the Atlantic coast of Canada all belong to a 

 single race or^type, or is it possible to distinguish several races in these waters? 



2. Does the rate of growth vary (according to the conditions of the waters 

 along the coast) ? Can types of different growth be distinguished and defined ? 



3. Is the renewal of the stock of herring of a constant character, or are 

 there the same great fluctuations in the stock (in the number of individuals 

 belonging to the different year-classes) as in European waters? 



A small portion of the material collected consists of biometrical observations., 

 i. e., determinations of number of vertebrae, number of fin rays, and number of keel 

 scales, these being characters which, as Heincke has shown, may serve as a basis for 

 morphological distinctions between different tribes or races of herring. The greater 

 part of the material consists of observations as to length, weight, sex, state of sexual 

 organs, and fat, accompanied by scale samples serving for determinations as to age 

 and growth. 



The material embraces a considerable geographical area, including, as it does, 

 samples from southern waters of Canada (including a series from Gloucester, Mass., 

 U.S.A.), Bay of Fundy, Nova Scotia, Cape Breton island, Newfoundland, Magdalen 

 islands, Northumberland strait and as far north as the Gaspe waters. In some of these 

 localities, moreover, the collection of material extended over several seasons, and there 

 are also various samples taken with different fishing implements. 



The results arrived at on examination of this material will be describetl in the 

 following pages. From the nature of the material itself, the greatest weight will 

 necessarily be attached to the discussion of that portion which deals with the age and 

 growth of the fish, as indicated by the state of the scales. A brief preliminary des- 

 cription and explanation will therefore be given as to the methods employed in scale 

 investigations, with observations as to the practicability of the method for dealing 

 with the herring in transatlantic waters. 



II.— METHODS OF AGE DETERMINATION AND GROWTH MEASURE- 

 MENT IN HERRING. 



It was early discovered that t3ie bony parts of fish were built up in layers, 

 resembling the annual rings visible in the trunk of a tree, and as far back as the 

 eighteenth century, the suggestion was advanced that it might prove possible, by 



SI 



