Garstang : The Disappearance of the Plaice. 405 



they are two and three years, still further seaward, including 

 the Lower Scruff and the Lowestoft Deep Water, they are three 

 to four years, on the south part of the Dogger three to five years, 

 further seaward on the north part of the Dogger, on the west of 

 the great Fisherbank, four to five years, and then above the Gut 

 four to six years old. The fish are in large numbers in the first 

 zone, but as they move seawards and increase in size they also 

 decrease in numbers. Experiments show that whereas 1000 

 fish twelve inches in length are secured in an hour's fishing on 

 the east side of the North Sea, only 50 per hour are caught 

 further out to sea. This was in the Spring of the year. From 

 July to December the mass of fish had moved a little further 

 from the coast into the sea. 



Below eight inches the males exceed in number, above that 

 size the males lose their preponderance, at fourteen inches they 

 rapidly fall off, and over eighteen inches there are practically 

 no males at all to be found. 



The mass of White Sea plaice is found to be mature ; the 

 number of mature plaice there enormously exceeding the num- 

 ber of immature plaice, and they extend over a very great 

 range of size. The average size at which the females become 

 mature there is sixteen inches, so that the females begin to 

 spawn at exactly the same size as in the North Sea. But on 

 examining the otoliths of these sixteen-inch fish in the White 

 Sea they are found to be very much older than the sixteen-inch 

 North Sea fish, so that they grow very much more slowly. A 

 White Sea female plaice begins to breed at the age of eleven or 

 twelve years, whereas in the North Sea they begin at six years. 

 The males begin to breed in the White Sea at eight or nine years 

 of age. The plaice there are very considerable in number until 

 they are twenty-two inches in length, and they are then not 

 less than twenty years old. From these and similar facts, 

 it might safely be inferred that on a virgin fishing ground, 

 like the White Sea, the males continue to spawn in practically 

 undiminished numbers for at least five years, and the females 

 for at least eight years. In the North Sea there are practically 

 no males over eight years, whereas the females occasionally 

 grow to be twenty years old, but such are extremely scarce; 

 they are twenty-four inches in length at least. The bulk of 

 the fish found on the central grounds of the North Sea are 

 immature. 



Of 6147 fish caught and marked, and then liberated in the 



1909 Dec. I. 



