Biology
The main spawning areas for plaice in the Irish Sea are off the coast of North Wales, between the Isle of Man and Cumbria, and off the north-east coast of Ireland between Dublin in the south and Dundrum Bay in the north. Plaice eggs were found in Cardigan Bay during surveys conducted before 1995, but recent work indicates only limited spawning occurs in this area. Spawning takes place mainly during March, although plaice eggs have been found in the plankton as late as May.
Fishery
Plaice are mainly caught by otter trawls, as part of a mixed whitefish fishery, and as a bycatch in the beam-trawl fishery for sole. The main fishery is concentrated in the northeast Irish Sea off North Wales, Lancashire and Cumbria. Although plaice are taken throughout the year, landings are higher between May and November when recruiting or early maturing fish are more plentiful on the shallower grounds inshore. The fisheries for plaice in the Irish Sea mainly involve vessels from the bordering countries: England, Wales, Scotland and Northern Ireland report 40% of the total landings of plaice in ICES Division VIIa, Ireland also accounts for 40%, Belgium 18%, and the Netherlands and France take the remaining 2%. In the late 1980s effort of the UK and Belgian beamtrawl fleets increased but has declined in recent years.