520 BULLETIN OF THE BUREAU OF FISHERIES 



locality. Nevertheless temperature is probably the factor that governs the range 

 and local abundance of the species, it being only where the surface temperature 

 rises to 55° or higher in summer, as is the case in Massachusetts Bay, Casco Bay, 

 Minas Channel, and over the southern shallows of the Gulf of St. Lawrence, that it 

 is able to maintain itself in any numbers. This is because its eggs and perhaps 

 its young larva? can not develop in lower temperatures. These few centers of 

 reproduction are not sufficiently productive to stock the intervening stretches of 

 shore line in the case of so stationary a fish, and for this reason the distribution of 

 this flounder is somewhat analagous to that of the oyster. 



Breeding habits. — Ripe fish are taken at Woods Hole in May and June, and as 

 Welsh found the sand flounder spawning late in June at Gloucester no doubt it is a 

 late spring and summer spawner in the Gulf of Maine. The evidence of these 

 Gloucester specimens proves that it breeds in the Massachusetts Bay region, while 

 its local abundance suggests the same for Casco Bay, as does the capture of its 

 larvae for Minas Channel. It may also breed to some extent at the heads of the 

 warmer and shoaler bays between Casco Bay and Grand Manan, but probably it 

 does not do so in any of the estuaries on the New Brunswick side of the Bay of 

 Fundy for no larva? have ever been found in Passamaquoddy Bay, a fairly repre- 

 sentative situation. 



Although it is not yet possible to lay down the extremes of temperature within 

 which this flounder can spawn, it is certain that its eggs develop only in rather warm 

 water, 50° to 60° having been found favorable for hatching at Woods Hole and 

 Gloucester, with eyen 70° not too high for successful incubation. Thus no part of 

 the Gulf of Maine is too warm for it, but the outer coastal waters east of Penobscot 

 Bay as a whole and most of the Bay of Fundy are probably too cold for successful 

 reproduction. 



Being so closely confined to the immediate neighborhood of the coast and to 

 the shoal water, the spawning of the sand flounder necessarily takes place in water 

 of low salinity, with about 32 to 32.5 per mille as the maximum in the Gulf of Maine. 

 The eggs are spherical, transparent, buoyant, and 1 to 1.08 mm. in diameter 

 (measurements taken at Gloucester by Welsh), with a single colorless or pale lemon 

 oil globule of 0.15 to 0.18 mm., and with the surface of the egg showing faint irregular 

 markings. Incubation occupies about eight days at 51° to 56°. Its duration has 

 not been recorded for higher temperatures. The larval stages have not been de- 

 scribed, though plentiful at Woods Hole, but the sand flounder, like the winter 

 flounder, completes its metamorphosis while smaller than dab (p. 500) or witch 

 (p. 516), for not only are the vertical fin rays complete and the ventrals formed in 

 specimen only 8}4 mm. (fig. 270) , but the right eye had already moved to the back 

 line of the head, and at 10 mm. the migration of the eye is completed and the fry 

 are ready to take to bottom. 93 



Commercial importance. — Although this fish is as good on the table as any other 

 flounder so far as flavor goes, it is so small and so thin-bodied that it is never likely 

 to be in demand. 



m Williams. Bulletin, Museum of Comparative Zoology at Harvard College, Vol. XL, 1902-1803, p. 2. 



