— 26 — 



Extremely characteristic of the composition of the landings from the individual 

 size-classes is the manner in which the number of plaice — from the value of greatest 

 density of the series, 25 cm. — decrease with size and age. The decrease is very 

 rapid, but not regular, differing in power for the different age- and size-classes. Some 

 idea of this can be obtained from the following series, which indicates the percentage' 



7c 

 10 f 



9 



8 



7 -■ 



•« - 



3 -■ 



Z ■■ 



1 - 



w 



■ s 



■■ 7 



- 6 



■ 4 



f ' I . I 

 70 75 an^. 



Age, 



Fig. 5. English Market-Measurements. Und Year, October 1906/07. Analysis by length and weight of all 



plaice measured in English ports (1,775,658). / length curve; w weight curve. — Percentage curves. 



D Mode, C Median, A Arithmetic average of / 



Di — Ci — oi w 



in a landing of such plaice as exceed a certain length in cm. and have passed a certain 

 average age. 

 Thus: 



over cm. long 25 — 30 — 3$ — 40 — 45 — 



more than years 3.5 — 4 — S — 6 — 7 — 



Percent of total . 



59 



25 — 



10 



— S 



