SEA-FISHERIES LABORATORY. 



185 



jyiay CTuNe ~JTny~ r 7TUgusT r ~BepT. 



Fig. 3. 



Mean lengths of plaice of age-group II $ $ taken in Barrow 

 and Fleetwood Channels in 1909-13. 



As in the former Table the statistical errors of the 

 means, and the mean error of the differences between any 

 two means, are calculated in order to show that the means 

 are reliable to a very considerable degree. All the 

 evidence we have seems to show that these fishing grounds 

 harbour a non-migratory population, which is recruited 

 from the " nurseries " in Morecambe Bay. When food is 

 abundant, the plaice concentrate on certain restricted parts 

 of these fishing grounds, and when food is relatively scarce 

 the fish are more sparsely, but more regularly distributed, 

 but this appears to be the extent of their movements 

 during the first three years of life. The connection 

 between the abundance of the food and the abundance of 

 plaice is very strikingly shown by a Table prepared by 

 A. Scott,* which shows that plaice are relatively abundant 

 when mussels are scarce and vice versa: — 



1906 plaice landed at Piel, 311 cwts ; 



mussels landed, 256 cwts. 



1907 



709 „ 



64 „ 



1908 



2,443 „ 



85 „ 



1909 



2,532 „ 



„ 



1910 



1,184 „ 



o „ 



1911 



1,010 „ 



o „ 



1912 



778 „ 



4,313 „ 



* Quarterly Report on the Scientific Work of the Lancashire and Western Sea 

 Fisheries Committee, October, 1913. 



