252 BRITISH FISHERIES 



These figures apply to the closed areas only. 

 They represent large numbers of hauls spread 

 over a number of stations and over five-yearly 

 periods, and so accidental flunctuations and minor 

 inequalities have no effect on the conclusions. 

 The latter are: (i) During the ten years the 

 numbers of plaice and lemon soles, both valuable 

 food-fishes, had decreased to a considerable extent ; 

 and (2) during the same time, and on the same 

 grounds, dabs and long rough dabs, both relatively 

 worthless fishes, had increased to an equally 

 noticeable extent. 



Now, these results are unintelligible unless we 

 remember some peculiarities in the life-histories 

 of the two categories of fish. Plaice and lemon 

 soles are fishes which spawn at some distance 

 from land and in deep water. Besides, they are 

 relatively large fishes, and mature individuals, if 

 they get into a trawl-net, are always captured. 

 Therefore the mature individuals were captured 

 on the offshore open grounds by the commercial 

 trawlers. The shallow inshore waters should have 

 been replenished from these offshore grounds, and, 

 because of the increasing exploitation of the latter, 

 they suffered to the extent indicated by the table. 

 The dabs and long rough dabs, on the other hand, 

 spawn to a considerable extent on the shallow 

 inshore waters, and the latter are replenished from 

 their own stock. Even on the offshore grounds 

 many mature dabs escape capture, because they 



