cfthe Fishery Board for Scotland 141 



III.— THE RATE OF GROWTH OF FISHES. By Dr. T. Wemtss 



Fulton, F.R S.E., Superintendent of Scientific investigations. 



(Plates YI.-XII.) 



Contents. 



1. Introductory, . . . , 



2. The Relation of Length to Weight, 



3. The Average Size at Maturity, 



4. The Influence of Temperature on Growth, 



5. The Sprat, . . . . , 



6. The Witch, . . . . , 



7. The Norway Pout; . . . , 



8. The Sharp- tailed Lumpenus, 



Page. 

 141 

 142 

 150 

 159 

 171 

 186 

 195 

 202 

 Tables showing the Relation of Length to Weight, . 205 



1. Introduction. 



The present paper contains the results of further observations I have 

 made on the rate of growth of fishes, and is a continuation of the investi- 

 gation on this subject as dealt with in some of the preceding Reports of 

 the Fishery Board. In that for 1901 I described fully the methods 

 adopted,* the collections being obtained by the use of a fine-meshed net 

 around the cod-end of the otter trawl, on the occasions when steam- 

 trawlers were employed in the trawling investigations in the Moray 

 Firth and Aberdeen Bay. It need only be mentioned here that the 

 fishes are measured in millimetres, the measurements tabulated, and 

 curves formed on the measurements as grouped into 1cm. or "Scm. 

 groups. It may be stated that the method of collection with a small- 

 meshed net in the way described has now been adopted in some other 

 countries as well as on- the " Goldseeker,'"' the vessel employed in the 

 Scottish part of the international investigations of the North Sea. 



In addition to the measurements of numerous fishes, only part of which 

 are worked up in this paper, viz. those dealing with the sprat, the witch, 

 the Norway pout, and the sharp-tailed Lujnjyenus, observations were also 

 made on a large scale with the view of determining the relation between 

 the weight and the length of a considerable number of species, and these 

 are detailed below. I have found that the law which governs the relation 

 between the weight and dimensions of similarly-shaped bodies does not 

 apply with precision to fishes. They increase in weight more than the 

 increase in length would, according to the law, imply, and since the number 

 of fishes in which the relation between the length and weight has been 

 determined was large, viz. 5675, belonging to nineteen species, and in no 

 case has the law been found to apply exactly, it appears to be well-established 

 that on the assumption that the specific gravity of the fishes does not 

 change during growth they must increase in some other of their dimensions, 

 whether breadth or thickness, in greater proportion than they increase in 

 length. 



* Twentieth Ann. Rep., Pt. III., p. 326. 



