242 THE SEA FISHERIES 



the herring and mackerel. Even the herring is probably returning 

 to its native place for spawning purposes. 



In the Irish Sea itself the percentage of recaptured fish is in- 

 variably high, e.g. in the Newcome Knoll (Mersey Estuary), experi- 

 ment in November, the percentage returned was 40, off Blackpool, 

 also in November, percentage returned 50, Morecambe Bay March 

 percentage returned 47. Many other instances could be given ; on 

 the whole in the eastern portion of the Irish Sea from 30 to 40 per 

 cent of the marked fish have been traced. In Cardigan and Car- 

 narvon Bays a far smaller proportion of the plaice were returned. 



In the Irish Sea there is a broad distinction between summer and 

 winter migrations, the former including those made from June to 

 September, the latter from October to May. In the summer months 

 the larger plaice move from the shallow waters inshore to the 

 deeper and cooler waters offshore. The plaice fishery, which is 

 carried on by the Southport half-decked cutters from Nelson 

 Buoy off the entrance to the Ribble, down towards the Liverpool 

 Bar and Northwest Lightships, is for fish which have moved out 

 from the shallow waters of the channels and estuaries. The winter 

 movements of plaice below 10 in. in length are mainly food migra- 

 tions, or may be caused by the variations of the sea temperature 

 along the coast. These movements are alongshore, and follow no 

 definite ascertainable order. 



The winter migrations of the larger plaice are almost certainly 

 spawning migrations. The only large spawning ground for this 

 species in the Irish Sea east of the Isle of Man is to the north-east 

 of Douglas, where there is a regular winter fishery. The spawning 

 plai,ce caught here by the trawlers have migrated outwards from 

 Morecambe and Liverpool Bays, and to a less extent from the 

 Solway, Luce Bay and the Firth of Clyde. A large number of fish 

 have been marked and liberated in Luce Bay, which is an area 

 closed to trawling by the Scottish Fishery Board, and enough have 

 been returned to show that the waters of this bay serve as a reserve 

 area for mature fish, which move offshore to spawn in the early 

 spring, when the sea temperature in Luce Bay is much below that 

 of the deeper offshore waters. 



Another considerable winter plaice fishery exists in Redwharf 

 Bay, off the North coast of Anglesea. This generally lasts from 

 November to January, when the bay is sheltered from the pre- 

 vailing south-westerly winds. It is believed that the commencement 

 and duration of this fishery depend on the temperature and other 

 physical conditions of the sea water. The fish marking experiments 

 have thrown considerable light on the condition of this fishery. 

 It appears there are two main groups of plaice caught in Redwharf 



