1 ! 



Part III. — Twenty-fourth Annual Report 



trawlers employed in the trawling investigations, as previously 

 described, and is the same method as that which has since been 

 used so extensively in the course of the international investigations 

 in the North Sea. During the course of the investigation, which 

 has extended over six years, the numbers of the chief species dealt 

 with have been as follows : — 



Plaice, . . . 17,950 



Common Dab, . 26,230 



Long Rough Dab, . 20,261 



Cod, . . . 7,176 



Haddock, . . 28,760 



Whiting, . . 58,164 



Gurnard, . . 5,495 



Norway Pout, . 7,192 



Herring, . . 19,806 



Sprat, . . . 6,473 



From a study of the growth of the different fishes and the size 

 at which they attain maturity, a law of growth is stated, namely, 

 that fishes approximately double their size and increase their 

 weight about eight times after they have reached sexual maturity. 



The species whose growth and age are specially dealt with in 

 the paper are the plaice, dab, flounder, lemon dab, long rough dab, 

 turbot, brill, cod, haddock, whiting, and grey gurnard. A general 

 conclusion is that fishes do not grow so quickly as is generally 

 supposed. Thus, while the plaice reaches a length of about three 

 inches in the first year of its life, the female is five years old and 

 the male four years when they attain maturity. It is estimated 

 that the turbot does not spawn until it is at least seven years old, 

 while the cod spawns at four or five years, the haddock at three, 

 and the whiting when two years of age. The paper is accompanied 

 by a number of tables of measurements and two plates. 



In connection with the question of the growth of fishes, a research 

 on the rate of digestion by Dr. Noel Paton, whose investigations on 

 the salmon are so well known, is in progress. Two sets of observa- 

 tions have been made, but the final results are reserved for next 

 year's Report. 



The Tay Sprat Fishery. 



Mr. John Fletcher contributes a paper on the sprat fishery in 

 the Tay, similar to the one published last year, but dealing with 

 the winter of 1905-1906. The fishery was again a comparative 

 failure, only 1371 crans of sprats, including young herrings, being 

 taken. The estimated number of young herrings caught in the 

 sprat fishing is stated to have been nearly 12,000,000, while the 

 sprats are estimated at a little over 16,000,000, the estimated 

 percentage of young herrings amounting to 42*4. 



The Specific Characters of the Gadim. 



Dr. Williamson contributes a paper, illustrated with three plates, 

 on the classification of certain members of the cod-family, viz., the 

 bib, or whiting-pout, the poor-cod, and the Norway pout, the paper 

 being a continuation of a previous one, in which the cod, the 

 saithe, and the lythe were dealt with. Two of the species, the 

 whiting-pout and the poor-cod, have often been confused, certain 



