SEA-FISHERIES LABORATORY. 239 
be made in the channels just off-shore: the fish are now 
migrating out into deeper water, and it is partly these 
fish which go to populate the ‘‘ Liverpool Bay’’ area. 
Later in the year this population becomes thinned out, 
partly by the intense trawling, but also by emigration 
to more off-shore grounds, and so we find that the 
larger of the plaice liberated in the shallow Morecambe 
Bay waters finally reach the grounds to the North-East 
of Isle of Man. The first migration from the Bay to the 
off-shore waters of the ‘‘ Liverpool Bay’’. area is a 
‘‘feeding migration’’; the latter movement to the 
North is a “‘ spawning migration,’’ and it is principally 
on the “‘ Bahama Bank’’ area that sexually mature 
plaice are to be found in the eastern side of the Irish 
Sea. 
3. Liverpool Bay. Charts III and IV. 
Two groups of experiments are considered. The 
summer experiments were made during the months of 
June and July, 1905-6-7, and the greater number of the 
plaice marked were caught and liberated near the 
“ Nelson Buoy,’ off the estuary of the Ribble (but see 
p. 288). In all 322 fishes were marked, and of these 117, 
or 36 per cent., have been traced. The chart shows that 
most of the fishes recaptured had migrated off-shore into 
the ‘‘ Liverpool Bay’’ area. The migration paths 
during the summer months are not extensive ones, but 
there is a general trend of the fish to the West and 
North. The modal length of these summer-caught 
plaice was about 245 cms. There are two principal 
winter migrations: (1) alongshore, most of the fish 
remaining in relatively shallow water: the mean 
length of these winter-caught plaice is 26°5 cms., the 
difference between this length and that of the summer- 
