FISHES OF THE GULF OF MAINE 



253 



two larval halibut, 20 and 21.5 mm. long, taken 

 close in to the southern coast of Nova Scotia in 

 shoal water, 46 suggests that the American fish may 

 spawn at least as shoal as the Pacific fish does, and 

 perhaps even shoaler. 



The eggs are buoyant, drifting suspended in the 

 water at depths greater than 30 to 50 fathoms, not 

 at the surface. Usually they are 3 to 3.8 mm. in 

 diameter, and they do not have any oil globule.* 9 



The only other buoyant fish eggs equally large 

 that are likely to be found in the Gulf of Maine are 

 those of the Argentine (p. 140), but these have a 

 large oil globule, so there is no danger of mistaking 

 them for halibut eggs. The buoyant eggs of the 

 Greenland halibut (p. 258) are larger still. 47 



In the Trondhjem aquarium the incubation of 

 artificially fertilized eggs occupied 16 days at a 

 temperature of about 43° (6° C.). The larvae were 

 6.5 to 7 mm. long at hatching, with very large yolk 

 sac and no pigment, growing to about 8.5 mm. by 

 the sixth day, and developing pigment by the 10th 

 day. 48 



The smallest naturally hatched Atlantic halibut 

 yet seen 49 was 13.5 mm. long, with the vertical fin 

 rays appearing. The dorsal and anal fins are 

 developed and the ventral fins are visible at about 

 22 mm. (fig. 125), by which time the left eye has 

 moved upward until its margin is just visible above 

 the contour of the head, forecasting that the 

 fish is to be a right-handed flatfish. Fish of this 

 size also show the large mouth characteristic of the 

 species. Up to this stage there is little pigment. 

 About one-fourth of the eye appears above the 

 profile when the little halibut is about 27 mm. 

 long, but even at 34 mm. (the largest pelagic stage 

 yet found) the eye has not entirely completed its 

 migration (fig. 126), though the pigmentation is 



« Contrib. Canadian Biol., N. Ser., vol. 1, No. 21, 1924, pp. 409-412. 



*' For description of eggs artificially fertilized in the Trondhjem aquarium, 

 see Rollefsen, Kgl. Norske Vidensk. Selsk. Forh., vol. 7, No. 7, 1934, p. 20-23; 

 for descriptions of naturally spawned eggs taken In tow nets in Icelandic 

 waters, see Tanlng, Meddel. Komm. Danmarks Fisk. Havunders. Ser. 

 Flskeri, vol. 10, No. 4, 1936, p. 5; for description of the eggs and larvae of the 

 closely allied Pacific halibut, see Thompson and Van Cleve, Rept. No. 9, 

 Internat. Fisheries Comm., 1936. 



" 4 to 4.S mm. in diameter according to Jensen, Kgl. Dansk Vidensk. 

 Selsk. Skr. Nat., afd. 9, R . 6, 1935, p. 4. 



«• For illustration of these artificially fertilized eggs In incubation stages, 

 and of the larvae hatched from them, see Rollefsen, Kgl. Norske Vidensk. 

 Selsk. Forhand., vol. 7, No. 7, 1934. 



" What little we know of the early stages of the halibut is due to European 

 students, chiefly to Schmidt (Meddel. Komm. Havunder-sjlgelser, Ser. 

 Flskeri, vol. I, No. 3, 1904), to Jespersen (Ibid., vol. S, No. fi, 1917), and to 

 Tanlng, (Meddel. Komm. Danmarks Fisk. Havunders^gleser, Ser. Flskeri, 

 vol. 10, No. 4, 1936.) 



stronger on the right side than on the left, and the 

 caudal fin (previously rounded) has become square 

 tipped. 



Figure 124. — Larva, 16.2 mm. (European). 

 Schmidt. 



After 



Figure 125. — Larva, 22 mm. (European). After Schmidt. 



Figure 126. — Larva, 34 mm. (European). After Schmidt. 

 Halibut (Hippoglossus hippoglossus). 



The younger larvae (up to about 25 mm. in 

 length) are made recognizable as halibut by their 

 curiously upturned snout. Older ones that are 

 large enough to show that they belong to some 

 right-handed large-mouthed flounder are separable 

 from the American dab larvae (the only other 

 common Gulf of Maine flatfish with which they 

 agree in both these respects) by the outlines of the 

 head and abdomen. 



The early life history of the Pacific halibut has 

 been worked out especially by Thompson and Van 

 Cleve, who have given an excellent series of illus- 

 trations of successive stages from newly hatched 

 larvae to young fry a little more than 1 inch long. 60 

 How long the young halibut lives adrift at the 

 mercy of the currents, is not known. But the 

 young fry, so small (47-64 mm long) that they had 

 evidently been spawned the preceding spring or 



*> Rept. No. 9, International Fisheries Commission, 1936, figs. 38-49. 



