SEA-FISHERIES LABORATORY. 241 



more profitable to refrain from catching small plaice near the 

 territorial limits because these small fish will become big ones 

 a year or so later, and then the big fish can be caught on the 

 more distant grounds. The argument runs thus : Small plaice 

 of about 25 cms. migrate out from the shallow- water grounds, 

 and they grow more quickly when they so migrate. Thus an 

 hundredweight of plaice of 25 cms. in length will become 

 about 1 J cwts. of plaice of 30 cms. long as the result of a year's 

 growth. Better then not to catch the fish until they are 30 cms. 

 long, for then they are worth much more in the markets. 



And certainly the data given in the foregoing pages do 

 seem to lend some support to the kind of argument indicated 

 above. Out of every 100 plaice marked and liberated on the 

 Nelson Buoy grounds in the summer months about 2 migrate 

 into the Red Wharf- Beaumaris Bay region in the latter months 

 of the year. These are the bigger fish and their mean size is 

 about 25 cms., whereas the mean size of all the fish when marked 

 on the Nelson Buoy grounds is about 21 cms. Next we mark 

 and liberate plaice caught on the Red Wharf-Beaumaris Bay 

 grounds, and we find that out of every 100, 9 are caught on 

 the southern grounds — in Carnarvon and Cardigan Bays, in 

 St. George's Channel, in the Bristol Channel, and on the S.E. 

 Coast of Ireland. These also are bigger plaice than those that 

 were marked : their mean length is 30 cms. as against 24 cms. 

 Therefore about r \>th % of the percentage of the small fish that 

 inhabit the nursery grounds in Liverpool Bay can be shown to 

 migrate and grow up during the two to three years following 

 the date of liberation into medium and large fish. Protect a 

 large quantity of the small plaice from being caughl on the 

 nurseries and we therefore get a small, additional quantity on 

 the offshore grounds, where the fish run much bigger in size. 

 This, we take it, is the argument lor the imposition of size 

 limits. 

 Q 



