SEA-FISHERIES LABORATORY. 151 



question, for or against a 6-inch mesh, may depend on 

 future investigation. If the fish measurements carried 

 out during 1909 are repeated, on at least an equally large 

 scale in 1914, say, and if there were to be a significant 

 decrease in the average and modal sizes of plaice caught 

 by means of a 6-inch trawl-net in that year, then the 

 whole question will be looked at from quite another 

 aspect, and restriction of the powers of capture might be 

 conceivably necessary. 



7. SIZES AT SEXUAL MATURITY. 



Mature plaice are commoner in in-shore Lancashire 

 waters than snakes are in Iceland, but one cannot say 

 much more than this. Of some 2,500 plaice dissected 

 in the Liverpool and Piel Laboratory less than 50 were 

 identified as sexually mature. Spanning plaice are not 

 found in in-shore waters, and nowhere in the whole Irish 

 Sea in relative abundance except on the fishing grounds 

 about and between the Selker and Bahama Light Vessels. 

 Doubtless they exist elsewhere, but in very small 

 numbers ; and it is quite likely that the majority of the 

 young plaice inhabiting the nurseries on the Lancashire 

 and Cheshire coasts are spawned to the South- West, in 

 the St. George's Channel and in the large Welsh bays. 

 Probably by much the smaller proportion comes from 

 the spawning grounds between Cumberland and the North 

 end of the Isle of Man. 



In the late summer and autumn large mature plaice 

 immigrate for a month or two into shallow waters, and 

 such, fish may be taken in Barrow Channel, Morecambe 

 Bay, in the llibble, and off the coasts and in the estuaries 

 of North Wales. It is mainly such fish that are handled 

 in the samples reaching us. The numbers are too small 

 to be treated statistically. 



