FISHES OF THE GULF OF MAINE 405 



The number of eggs produced by the female pollock varies with the size of the 

 individual fish. The average is about 225,000, but more than 4,000,000 eggs have 

 been found in one fish of 23J/2 pounds. The egg is buoyant, Mdthout oil globule, and 

 averages about 1.15 mm. in diameter. It is thus decidedly smaller than the egg of 

 the cod or haddock. Incubation occupies 9 days at a temperature of 43°; 6 days 

 at 49°. As development proceeds black pigment cells appear along the sides of the 

 embryo and on the adjacent portions of the yolk, and by hatching time these are 

 scattered over the whole surface of the embryo. 



The larviB are about 3.4 to 3.8 mm. long at hatching, slender, with large yolk 

 sac, and sprinkled with black pigment cells, with the vent situated on one side at 

 the base of the ventral fin fold, as it is in other larval gadoids. At first the little 

 pollock float with yolk uppermost but they right themselves as the yolk shrinks. 

 About 5 days' time are required for the entire absorption of the yolk sac and for the 

 formation of the mouth, during w^hich period the pigment of the post-anal section 

 of the trunk becomes grouped in longitudinal bars, two dorsal and two ventral, the 

 former longer than the latter. At this stage pollock closely resemble cod of the 

 same size, but in the latter the ventral bars are longer than the dorsal ones opposite 

 them, and usually three in number instead of two. These bars persist until the 

 pollock grows to a length of about 15 mm., when the pigment becomes more scattered. 

 The caudal fin rays appear at about 9 mm., all the dorsal and anal rays and the 

 ventral fins at about 15 mm., the vertical fins are separate from one another at 

 20 mm. (that is, at about 2 months), and fry of 25 to 30 mm. show most of the 

 characters of the adult. 



In European seas the young pollock lives pelagic near the surface for its first 

 three months, corresponding to which the young fish have been taken in the 

 tow nets at Woods Hole from January to May and are to be expected in Massachu- 

 setts Bay then, though we have no actual record of them there. At Woods Hole, 

 furthermore, the fry are about 1}4 inches long in April, which no doubt applies 

 equally north of Cape Cod. The later growth has been discussed already (p. 401). 



The migrations of the young fish from hatching until they appear on the coast 

 as yearlings are of special interest in the case of the pollock because of the strong 

 probability that the multitudes of these fish, large and small, that frequent the 

 eastern coast of Maine are produced elsewhere, which, if correct, entails a consider- 

 able return journey on the part of the young fish. Our own observations throw 

 no direct light on this phase of their lives, but the general circulation of the Gulf 

 suggests that larvse hatched anywhere along the coast south of Cape Elizabeth 

 would drift southward, either to swing offshore toward the southeastern part of 

 the Gulf, or to follow the shore past Cape Cod. The presence of an abundance of 

 pollock fry in spring at Woods Hole corroborates this, for pollock are not known 

 to spawn anywhere west of the Cape (p. 402). 



As the fish grow larger they become able to direct their swimming more effec- 

 tively, either in pursuit of food or in relation to the prevailing current, but no 

 evidence has yet been gathered as to whether the eastern coast of Maine and the 

 Bay of Fundy draw their abundant stock of pollock chiefly from the spawning 

 grounds of the Cape Elizabeth- Cape Cod region or whether, and in what proportion. 



