13 



Part III. — Twenty -second Annual Report 



species grow at the same rate, or attain the same size, the females, as a 

 rule, growing quicker and becoming bigger ; and the numbers of the sexes 

 in proportion to one another may vary. Thus, among the flat-fishes the 

 females grow more rapidly, as a whole, than the males, and reach a larger 

 size ; while among the gadoids the rate of growth and the relative 

 dimensions of the older forms appear to be, as far as ascertained, nearly or 

 quite uniform. This does not, however, very materially affect the 

 question of the limit at first maturity, since the males and females grow 

 with fairly equal uniformity until the reproductive stage is reached, but 

 in certain cases the male becomes mature at an earlier age than the 

 female and at a smaller size, and it is this which introduces complexity 

 and difficulty. It thus happens that among flat-fishes many more 

 females than males are landed, although the number of males at the stage 

 of reproduction may be equal to or greater than the number of females 

 on the fishing grounds. 



I have therefore prepared a statement of the limit between the mature 

 and the immature fishes of the various species, based upon the available 

 information, with consideration of the facts concerning the growth of the 

 fishes, which may be used in endeavouring approximately to determine 

 the proportion of the immature and the mature which are marketable, 

 as follows : — 



Whiting, 



- 8* 



Turbot, 



17 



Haddock, 



- 11 



Brill, - 



15 



Cod, - 



- 26 



Common Dab, 



6 



Plaice, - 



- 15 



Witch, 



12 



Lemon Dab, 



- 10 







With regard to the other point of the investigation, the proportions of 

 the fish at different sizes and weights which are landed, I have for a 

 considerable time past devoted attention to this subject, and have 

 measured and weighed a large number of fishes, amounting in the 

 aggregate to over twenty tons, as they are landed and sold. With some 

 kinds the average size and the limits of size are very regular, and these as 

 a rule belong to the more important species. The information thus 

 obtained as to the size and weight of the various classes of fish enables 

 a close approximation to be made as to the proportion of the mature and 

 immature, and thus a comparison instituted between these results and 

 the observations made on board the trawlers on the same subject. Tables 

 containing the particulars of the size and weight of the fish referred to 

 will be found appended to this paper (p. 89), and other information 

 relative to the size and weight is given in a paper on the rate of growth 

 of fishes {see p. 142). 



I have therefore made a series of calculations to show the proportion 

 of the mature and the immature fishes of certain kinds caught by 

 trawlers, the data being contained in the Tables and in preceding reports 

 of the Fishery Board, particularly the paper above referred to, and the 

 limit of size between the two classes being the biological one 

 as defined. 



There are marked differences in the proportions among different fishes. 

 As already stated in the case of the dab, all those which are marketable 

 are of mature size ; no immature individuals of this species are, therefore, 

 landed. Among plaice, all those classed as large, or firsts, are of adult 

 size, while all those belonging to the third, or small, class are under the 

 biological size and are immature. Among mediums a certain proportion 

 are immature, rather under one half in number being under the limit of 



