THE FLAT-FISH FAMILY 221 



in September, and even in January seven specimens of this size 

 were taken in stake-nets near Cleethorpes. These must have 

 been hatched many months before, and serve to show that the 

 growth of a few individuals produced late in the season may be 

 very much retarded. Such observations prove that the remark- 

 able difference in growth among flounders of the same age 

 observed in the experiments made at Plymouth occurs also 

 among plaice in the sea, and it is probably due to the same 

 cause in the two cases, namely competition for food. 



A sample of larger plaice taken in the Humber at a depth 

 of one to two fathoms at the end of March varied from 3^ to 

 1 1 inches in length, but the greatest number were between 7 

 and 9 inches. A sample consisting of 425 fish taken by a 

 shrimp trawler at the mouth of the same estuary in May was 

 examined, each fish being measured. The greatest number, 

 namely 265, were from 7 to 8 inches long, those at smaller sizes 

 being fewer. These must be considered as the year-old fish, 

 that is to say, as far as our present evidence goes, we may 

 consider that the length of the largest number of year-old 

 plaice in spring is 7 or 8 inches. By the reasoning previously 

 employed we may infer that the mid-size of the two-year-old 

 plaice in the North Sea is about 13 inches, and of the three- 

 year-old about 17 inches, at the latter size all but a small 

 proportion being mature. These latter estimates apply only 

 to females, the males being smaller. 



It is a notorious feature of the North Sea trawl fishery that 

 in the spring and summer months very large numbers of small 

 plaice are taken on what are known in the Humber ports as 

 the "eastern grounds," these small fish being landed at Hull, 

 Grimsby and London. These grounds extend along the con- 

 tinental coast from the Texel to the Horn Reef, and even 

 further northward towards Hantsholm on the coast of Denmark, 

 and from a depth of about five fathoms or even less to fifteen 

 fathoms or a little more. These grounds have a very slight 

 declivity and are for the most part level and sandy. Very few 

 of the small plaice taken on them exceed 1 5 inches in length 

 and the majority are from 7 to 13 inches. A small proportion 

 of the plaice taken in the trawl are less than 7 inches long, some 

 being as small as 5 inches, though those of this size are not 

 usually taken to market. These remarks apply to the earlier 



