74 THE SOLES 



as late as August, and these facts seem to indicate that the 

 journeys of the spawners and the time of their spawning 

 depend upon temperature. ^ Depth is not, apparently, an 

 important factor, as soles have spawned freely in the shallow 

 tanks at Plymouth. 



For some reason, perhaps because they overfed them, the 

 French investigators Fabre Domergue and Bietrix in 1905 

 failed to induce their captive soles to spawn at Concarneau, 

 but they collected eyed eggs from the sea, hatched '^ them and 

 reared the fry through the larval and post-larval periods to 

 the stage at which they began to forage for their own food. 

 It is now certain that soles could be transplanted, and prac- 

 tically certain that they could be hatched and reared on 

 a commercial scale ; and the tribe is so hardy and so valuable 

 that ' sole breeding ' is quite likely to be a serious business 

 proposition within a few years. Meanwhile of course the 

 development is well known. The eggs of the common sole are 

 about 0-04 to 005 inch in diameter. They are transparent 

 and provided with small oil globules. The eggs are hardy — 

 as is the fish at every stage of its existence — more so (even) 

 than the plaice. Meek gives the approximate period of 

 incubation as 10 days (temperature not stated), and Mcintosh 

 in 1897 noted that the yolk-sac (temperature was not stated) 

 was practically absorbed by the ninth day. The fry are then 

 one-tenth of an inch long. The fish begin to turn over on to 

 their right side at about one-fifth of an inch long, and are real 

 flat fish at two-fifths of an inch. 



The fry in the Thames Estuary are said to be 2| to SJ inches 

 long by their first October. Cunningham says that the fish 

 reach 6 to 7 inches in their first year, Fabre Domergue that they 

 are as much as 12 inches long at the age of two years ; and 

 Johnstone, that they are mature when they are about 12 inehes 

 long. All these remarks apply to the common sole. 



Dr. Lebour states that the young soles at Plymouth have 

 been found to live principally on the free swimming larvae of 

 barnacles (Balanus), and on copepods which live on the minute 

 plants in the upper layers of all seas. Young soles apparently 

 take copepods — they prefer Temora to all others — almost 

 as soon as they are katclied. 



The T kickback (Solea variegata), seldom exceeding 9 inches in 

 length, is a deep-water form. The French expeditions found 

 it at 168 fathoms. Very little information is available as to 



' British Marine Food Fishes, p. 894. 



^ Le Developpement de la Sole, 19U5 (Travail du Laboiatoiie de Z<Jologie 

 maritime de Concarneau). 



