RAPPORTS. XIII C 2: THOMPSON 



— 10 — 



fish. Judging by the curve of growth (fig. 5), so far as we now know it for the first tour 

 years, I judge these Moray Firth Cod to be for the most part six years old, with an in- 

 definite admixture of five-year-old and also of older fishes. It is quite clear that there has 

 been an exodus, or emigration, of fish from this region after the age of two years 

 old, and a return, or immigration, of Cod into the Moray Firth at about five years old 

 and upwards. 



Exactly the same phenomenon is shown on the curve for April to June (fig. 7); but 

 for the rest of the year (fig. 8, 9) the curves are quite destitute of this great and conspi- 

 cuous indication of the presence of large Cod, and show them to be present only in small 



240 



210 



180 



CO 



Li- 150 



I*— 

 o 



t_120 



(U 



§90 



Z 



60 

 30 



10 20 30 40 50 60 70 80 90 100 



Fig. 9. Sizes (and approximate ages) of Cod captured in the Moray Firth: October — December. 



numbers during the latter half of the year, just as was the normal condition in the Firth 

 of Forth. 



In figure 10 (A and B) we illustrate for the Moray Firth as well as for the Firth of Forth 

 the composition of the entire catch of Cod by the "Goldseeker", irrespective of season, but 

 excluding the catch of the small mesh net; but the curve is drawn not from the total 

 numbers of fish at each centimetre of size, but from the logarithms of these numbers; 

 that is to say, this curve is drawn upon the plan suggested by Mr. T. Edser in his recent 

 note on the "Number of Plaice at each length in the Southern part of the North Sea'". 

 In this curve we may note several things: firstly, the curve rises both for the Moray 

 Firth and for the Firth of Forth to a point corresponding with a size of about 26 or 27 



I Journal of the Roy. Statistical Society. 1910. 



