BAKENTS SEA IN AUGUST, 1907. 77 



the same length, but at the same time the rapid decrease after 44 cm., 

 and virtual disappearance after 49 cm., is surprising. 



In this recently spawned shoal the usual earlier maturity of the 

 sex* would account for tlie great numbers of males in tlie smaller 

 groups; for instance, in the 35-39 cm. group 96 per cent of the males 

 were mature, in contrast to only 11 per cent of the females. To only 

 a small extent would this account for the high percentage of males 

 being maintained in the next group, as only 8 per cent of the females 

 now remain immature. We must look for some other explanation, 

 which seems to me to lie in the probable infinitesimal annual growth 

 which the males now undergo. The fishes of this sex are now some 

 10 or more centimetres above the size I have estimated for first 

 maturity, after which stage in life' considerable retardation of growth 

 takes place, f It is probable, therefore, that in these slow growing 

 plaice (see p. 84) of the Barents Sea many year groups are comprised 

 in this arbitrary 40-44 cm. group. 



It is probable, too, that the rapid diminution in numbers and final 

 disappearance of males in the succeeding groups is accentuated by an 

 earlier mortality of the sex here, as in the North Sea.| Looking at 

 the curves of length frequencies it will be seen that the curve for the 

 males does fall more rapidly from its mode or maximum height (at 

 41 cm.) than does that for the females from its mode (at 47 cm.). 



The variation in the proportion of the sexes at individual stations 

 and groups of stations, as possibly giving a clue to migrations, is dealt 

 with later (p. 87). 



The curves, of length frequencies (Figs. 1 and 2) in the case of both 

 sexes, display remarkable regularity, representing an absolutely intact 

 stock of mature plaice, such as is to be found in no other region of 

 the world at present fished. A series of annual observations, tracing 

 the inevitable reduction of this stock by the influence of man, and a 

 contemporary study of this fishery's statistics in their modern im- 

 proved form, will throw interesting and valuable light on the 

 changing aspects of a plaice fishery. Icelandic waters cannot now 

 afford similar opportunities, for in the comparatively few years this 

 region has been exploited for plaice a marked reduction of the 

 original stock is observed by the fishermen to have occurred. 



* FuLTOX. Twentieth Annual Rexiort Fishery Board for Scotland, Part III, pp. 354- 

 60 (1902). 



Wallace. Preliminarij Investigations on the Age and Growth-Rate of Plaice. Nortli 

 Sea Investigation Committee, Report 2. Soutliern Area, 1902-3. Cd. 2670 (1905), 

 pp. 218, etc. 



t Wallace. Report on the Age and Growth-RcUe of Plaice in the Southeryi North Sea. 

 North Sea Investigation Committee. Second Report (Southern Area), 1904-5, Part I, 

 p. 33. + Wallace. Loc. cit., p. 34. 



