363 



North Sea Investigations. 



{Continued.) 



By 



Ernest W. L.. Holt, 



Naturalist on Staff in charge of Investigations. 



PAGE 



I. On the Relation of Size to Sexual Maturity in Pleuronectids . . 363 



II. Ou the Destruction of Immature Fish in the North Sea . . . 380 



III. Remedial Measures ..... . 388 



I. On the Eelation of Size to Sexual Maturity in Pleuronectids. 



Introductory. — I believe tliat^ so far as concerns the more im- 

 portant species, sufficient information has been accumulated to allow 

 of the deduction of a reliable conclusion. 



Though it is certain that some local variation exists in the differ- 

 ent parts of the North Sea, I have not found it possible to treat the 

 area otherwise than as a single district. This is of the less import- 

 ance since the variation seems to be very slight, and in any prac- 

 tical application of the results arrived at I do not see how it would 

 be feasible to subdivide the district. 



It again becomes my pleasing duty to acknowledge much courtesy 

 and assistance in carrying out my work. Without the permission 

 of owners to examine the larger and more valuable kinds of fish 

 without purchasing them, my records would be indeed meagre. I 

 shall not attempt to enumerate those who have helped me in this 

 way, as the list would comprise almost every smack-owner or fish 

 merchant in Grimsby. The greater part of the work has been 

 carried on, by kind permission of the Marine Fisheries Society of 

 Grimsby, at the Cleethorpes Hatchery. 



Scheme of "Work. — The scheme upon which my deductions are 

 based requires little explanation, since I have seen no good reason 

 to change the opinion which I have expressed in a report upon the 

 same subject for a different district (Sci. Proc. E. Dubl. S.,"^ vol. vii, 



* Reprinted from the Report of the Council Royal Dubl. Soc. for 1891, Feb., 1892. 



