FISHES OF THE GULF OF MAINE 491 



The yolk is absorbed about 5 days after hatching, when the larva has grown to 

 6.2 to 7.5 mm. in length. The caudal rays appear shortly after this, the dorsal 

 and anal rays at about 11 to 12 mm., and the 3 vertical fins are differentiated at 

 about 15 to 18 mm., by which stage the body has begun to assume the deep but 

 very thin form characteristic of all young flounders while the jaws have developed 

 sufficiently to show that the little fish belongs to one of the large-mouthed species. 

 The left eye may commence its migration when the larva is about 20 mm. long, 

 while Welsh found it visible above the outline of the snout in Gulf of Maine speci- 

 mens of 24 mm. and almost at the dorsal ridge at 34 mm., but in other seas larvae 

 as long as 35 mm. may still be symmetrical. The only other Gulf of Maine species 

 for which the larval plaice might be mistaken (except in its very earliest stages) 

 are the witch flounder and the halibut; but the witch is longer at corresponding 

 stages of development but with the distance from snout to vent proportionately 

 much shorter, and the outline of throat and abdomen are sufficiently different to 

 distinguish the plaice from the halibut (p. 481). 



Up to the time of its metamorphosis the young plaice lives pelagic, as do the 

 young of most sea fishes, keeping close to the surface at first but sinking deeper as 

 it grows, until finally it takes to the bottom. Young plaice, like many other pelegic 

 animals, sink more or less regularly by day, to rise toward the surface of the water 

 by night. 



Welsh's observations suggest that the plaice commences its life on the bottom 

 at a length of about 13^ to 1% inches, with its metamorphosis already complete, 

 its body scaly, and its eyed side densely pigmented. There is wide variation in 

 this respect, however, and according to European authors the fry may even take 

 to the bottom before the left eye has completed its migration around the head. 



The period occupied in larval growth and metamorphosis varies with tempera- 

 ture, probably about three to four months being a fair estimate for the Gulf of 

 Maine, where we have taken the pelagic larvas of the plaice as early in the season 

 as May 26 and as late as August 2 ; and by the first winter the little fish grow to a 

 length of 2 to 3 inches, their exact size depending upon how early in the season they 

 are hatched and probably on the temperature in which they live. 



Commercial importance. — Although the plaice is an excellent pan fish, in fact 

 one of the best of Gulf of Maine flounders, there is so little market for it that few 

 are brought in. 



168. Summer flounder (Paralichthys dentatus Linnaeus) 



Flounder; Fluke; Plaice; Plaicefish; Turbot 



Jordan and Evermann, 1896-1900, p. 2629. 



Description. — The summer flounder is left-handed. That is, it lies on the right 

 side with its eyes on the left side and its abdomen on the left edge as it rests on the 

 bottom (this differentiates it at a glance from the plaice), and it is large-mouthed 

 like the sand flounder, which is similarly left-handed (p. 516); but its two ventral 

 fins are alike and both are separated by a considerable space from the long anal, 

 whereas the upper ventral fin of the sand flounder is continuous with the anal. 

 The only Gulf of Maine flatfish with which the summer flounder shares its left- 



