222 SALT-WATER FISHES 



the fact that shrimp-trawlers catch young dabs of 3 in. or less 

 in the Thames estuary in October, and he is of opinion that 

 the smallest of these (measuring perhaps \\ in.) are at least 

 3|- months old, while the largest would be eight or nine 

 months. The market price of the dab is considerably lower 

 than that of the plaice, but it is quite equal as food to 

 the more popular fish. 



The Flounder (P. flesus), or Fluke, though correctly 

 reckoned among sea fish, has a partiality for brackish or even 

 fresh water in all but the spawning-period and finds its way 

 a long distance up many of our rivers. According to 

 Cunningham, it cannot, however, spawn in fresh water, for 

 its eggs, as already explained, must float in order to develo p 

 and they would be washed out to sea and dispersed in a 

 medium unfavourable to their development. 



The flounder may be distinguished by its small, smooth 

 scales, and by the fact of those behind the head and along 

 the bases of the fins being rough and spinous. In colour this 

 fish is very dark on the upper side and bright white beneath. 

 It was on the flounder that Cunningham made his interesting 

 experiment, already described, in artificial colouration by 

 reflected light. The flounder has from forty to forty-five fin- 

 rays in the ventral fin, fewer therefore than in either the plaice 

 or dab. The largest flounder on record probably measured 

 less than 20 in., though there is some difference of opinion 

 as to its maximum size. Day's estimate of 8 or 9 in. as 

 its greatest length is clearly a misprint for 18 or 19 in. 



The food of the flounder consists in great part of small 

 crustaceans and molluscs, while in the aquarium it takes 

 worms more readily than anything else. 



As usual in the flat-fishes, the female is slightly the larger 

 sex, but, according to the calculations of Dr. Fulton, the 

 males are considerably the more numerous, which is unusual. 



The flounder, which reaches maturity at a length of 7 in. 

 in the female and less than 5 in. in the male, spawns chiefly 



