SEA-FISHERIES LABORATORY. 309 



adaptation to change of temperature, or of salinity, or 

 of both. The total quantity of plaice in such an area as 

 the Irish Sea, with St. George's Channel, probably 

 remains much the same from year to year : if fish are 

 scarce on one particular fishing ground they are more 

 than usually abundant on others ; admitting, of course, 

 that a progressive slow change may occur, a change 

 which is nevertheless too gradual to produce a very 

 notable effect in the productivity of two successive 

 seasons. 



If this is the case, the relation between changes of 

 physical conditions and changes in the productivity of 

 the fisheries ought to become apparent by following up 

 the line of investigation suggested in the previous pages. 

 In order that it may be successful this method requires 

 a knowledge of accurately collected fishery statistics. 

 Fortunately, the system of collection adopted by the 

 Board of Agriculture and Fisheries some years ago 

 provides at least the machinery for the collection of these 

 data. The "D2" forms now in use by the Board's 

 Collectors of Statistics contain information with regard 

 to the quantity of each kind of fish landed by all first- 

 class fishing vessels (steamers and smacks) ; the duration 

 of the " voyage " ; and the locality of the ground fished 

 over. 



These "D2" forms for the years 1906-1912, and 

 for all landings of fish at the Port of Bangor, in North 

 Wales, have been sent to me by Dr. J. T. Jenkins, and 

 they have been examined and abstracts of the quantities 

 of plaice landed day by day, during this period, from the 

 fishing grounds off the coast of North Wales, have been 

 made. The grounds in question include Red Wharf Bay 

 itself, and the deeper water off-shore from it and Point 

 Lynus down to about 20 fathoms ; the fishing grounds in 



