240 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



throughout July in the Gulf of Maine, for we have 

 caught several nearly ripe females on Platts Bank 

 and around Boon Island at the end of that month, 

 though we have seen no perfectly ripe fish. In the 

 eastern Atlantic cusk spawn chiefly deeper than 

 100 fathoms, to judge from the distribution of the 

 eggs at the surface. But the chief production of 

 eggs probably takes place in shallower water in 

 the Gulf of Maine, since most of the stock lives 

 in lesser depths there. And some must spawn 

 close inshore, for we have taken cusk larvae only 

 6 to 13.8 mm. long off Cape Cod; in Provincetown 

 Harbor; and near the Isles of Shoals. 82 



We owe what is known of the eggs and larvae 

 to European students. The cusk is among the 

 more prolific of fishes, more than 2 million eggs 

 having been estimated in a female of medium size. 

 Their eggs are buoyant like those of other gadoids; 

 1.29 to 1.51 mm. in diameter, with one oil globule 

 of 0.23 to 0.3 mm.; and they may be recognized 

 by the brownish or pinkish color of the oil globule, 

 together with the fact that the entire surface of 

 the egg is finely pitted. 



The larvae are about 4 mm. long when they 

 hatch. The vent is situated at the base of the 

 ventral finfold as it is in other gadoids, but they 

 are separable from all other gadoid larvae that 

 occur in the Gulf of Maine by the pinkish oil 

 globule at the posterior end of the yolk. The 

 yolk is absorbed in about a week after hatching, 

 when the larvae are about 5 mm. long. The 

 ventral fins of the little cusk elongate as it grows, 

 like those of young hake and of young rockling, 

 besides becoming heavily pigmented with black. 

 But cusk larvae are separable from those of hake 

 and of rockling by the fact that their ventral fin 

 rays are separate one from another, and by the 

 presence of three patches of black pigment: one 

 on the top of the head; a second over the gut; 

 and a third at the tip of the tail, besides two 

 vertical black bands which divide the trunk behind 

 the head into three nearly equal sections. The 

 rockling has only one band of pigment behind the 

 vent, and neither of the hakes that are common 

 in the Gulf of Maine has a definite cross-band of 

 pigment. 



The first traces of the vertical fin rays of the 

 young cusk are visible at about 12.5 mm.; the 

 dorsal and anal fins are differentiated at about 28 



mm.; and it is at this stage that the ventrals are 

 at their longest, relatively. Fry of 40 mm. and 

 upward show most of the characters of the adult. 

 And the relationship of their dorsal and anal fins 

 to the caudal, and the presence of only one dorsal 

 fin and one anal fin is sufficient to identify them 

 from this stage on. 



Figure 116. — Egg (European). After Schmidt. 



Figure 117. — Larva, 6.8 mm. (European). After Schmidt. 



Figure 118. — Larva, 9.25 mm., off northern Cape Cod. 

 Cusk (Brosme brosme). 



The older cusk fry, while still living at the sur- 

 face, are described by Schmidt 83 as greenish yellow 

 with blue eyes, not silvery-sided. 



The young cusk drifts near the surface, as other 

 gadoids do, until it is 2 inches long or more, and 

 there is reason to believe that in European seas 

 they first seek the bottom in considerable depths. 

 But we have nothing to offer on this point for the 

 Gulf of Maine. 



•> The records are July 22, 1912, 1 specimen; July 20, 1916, 4 specimens; and 

 July 22, 1916, 1 specimen. 



1 Meddel. Kommis. for Ilavunderstfgelser, Serie Fiskeri, vol. 1, No. 8, 

 1905, p. 7. He also describes the larval stages of the cusk. 



