6 GEORGE V SESSIONAL PAPER No. 38a A. 1916 



VIII. 



THE LIFE-HISTORY OF THE HAKE (UROPHYCIS CHUSS Gill) AS 

 DETERMINED FROM ITS SCALES. 



By E. Horxe Craigie, University of Toronto. 

 (With Seven Figures.) 



The object of this investigation vpas to determine the rate of growth of the hake 

 by an examination of the scales and comparison of the data thus obtained with the 

 length-frequency curve. 



In all, 780 hake were examined, representing several different catches, as follows: 



No. 1. North Channel, June 15, 1914. 



Nos. 2-50. North Channel, July 7, 1914, in the afternoon. 



Nos. 53-100. Wilson's Beach, July 16, 1914. 



Nos. 101-228. Wilson's Beach, July 22, 1914. 



Nos. 229-352, Wilson's Beach, July 30, 1914. 



Nos. 363^780. Wilson's Beach, July 31, 1914. 



In the case of Nos. 1 to 52, inclusive, the length was recorded and scales were 

 taken. Nos. 53 to 227 were also weighed, and their sex, the weight of the gonads, 

 and the weight of the livers were recorded. In the remaining cases only the length 

 and sex were recorded, in order to get data for a length-frequency curve. 



The measurements of the first hundred fish were made with a folding rule, while 

 the remainder were measured by placing them upon a board marked off into centi- 

 metres. In every case the measurement was made from the tip of the snout to the 

 posterior end of the vertebral column. 



The scales were taken from the side of the fish either a little above the lateral 

 line or just below the dorsal fin. A considerable number were prepared by soaking in 

 water, cleaning thoroughly with a small brush, and mounting dry in microscope 

 slides. It was found, however, that they kept perfectly in paper, and could be exam- 

 ined quite readily, as when in permanent mounts, if simply wet, and placed upon a 

 clean slide, the surplus water then being removed with a piece of clean filter paper, 

 and this method was used in most of the work. 



Curves were drawn with the lengths of the fish as abscissae and the frequency 

 as ordinates. One such length-frequency curve was drawn for Nos. 53^-352 (fig. 1), 

 which will be seen to show a typical " hat curve " for each sex, that for the males 

 being particularly smooth and showing a predominance of fish 43 cm. long. The 

 curve for the females, on the other hand, shows a marked predominance of indi- 

 viduals between 47 cm. and ^0 cm. in length, the greatest number being 50 cm. One 

 curve drawn for both sexes shows two humps corresponding to those on the curves for 

 separate sexes, showing that there is not even sufficient overlapping of the sizes of 

 the two sexes to smooth out the curve. 



Graphs drawn for Nos. 353-780 (fig. 2) show even more strikingly regular " hat 

 curves," and also show the same difference between the predominating size of the two 

 sexes. From these graphs it appears, in the first place, that the fish of a given sex 

 associate almost entirely with individuals of their own age, as there is only one 

 marked hump in each curve. In the second place, it is evident that either the males 

 of the age represented are smaller than the females of the same age. or else the 



