FISHES OF THE GULF OF MAINE 443 



than a few degrees from its coldest for the year — that is to say, in temperatures of 

 35 to 40°. Allowing for annual variations, this gives an extreme range of from 

 about 35° to about 44° for the most active spawning over the Gulf of Maine as a 

 whole, temperatures considerably lower than those in which haddock spawn in 

 European waters (41 to 50°). 



The Gulf of Maine haddock likewise breeds in fresher water than does its 

 European congener and necessarily so, for the parts of the Gulf where haddock breed 

 are decidedly less saline at all levels and seasons than the spawning grounds in the 

 North Sea, around the Faroe Islands, or south and west of Iceland. Thus whether 

 it be on Georges Bank or Browns Bank or on the coastal grounds, most of the 

 spawning takes place in salinities of 32 to 32.5 per mille, with 34.5 per mille as about 

 the maximum for fish spawning deepest on the offshore slope of Georges Bank, and 

 31 per mille the minimum, whereas haddock in north European waters spawn chiefly 

 in water as saline as 34.5 to 35.5 per mille. 



Density of water. — The specific gravity of the water (the factor that determines 

 whether buoyant fish eggs float and develop or sink and die) is usually between 

 1.0255 and 1.0260 in the Gulf at the levels where fish live, both on the offshore banks 

 and along shore. So far as is known no haddock eggs are actually spawned in 

 water lighter than this and few in water as heavy as 1.0270, but the overlying water 

 may be very much fresher, and is often so light near shore at the time of the spring 

 freshets as to interfere with the operation of the hatcheries. Eggs artificially 

 fertilized on board the Albatross off Gloucester in May, 1913, proved to be very 

 nearly balanced in water of a specific gravity of 1.0232, with 1.0230 the critical 

 density for unfertilized as well as for fertilized and developing eggs, a result justi- 

 fying the hypothesis that in whatever part of the Gulf haddock eggs are deposited 

 they will rise from the bottom; and if they fail to reach the surface locally because 

 of its low density, they will merely float, balanced in the water, a few fathoms 

 down. Furthermore it is probable that eggs naturally spawned gradually lose in 

 specific gravity as they float upward into lighter and lighter water. 10 In short, 

 there is no reason to suppose that any of the haddock eggs produced in the Gulf are 

 lost by sinking, to smother on the bottom. 



The eggs of the haddock are buoyant, without oil globule, and from 1.19 to 

 1.72 mm. in diameter. Eggs taken at Gloucester in March, 1913, averaged 

 1.57 mm., varying from 1.47 to 1.72 mm. Thus they average slightly larger than 

 those of the cod. In early stages in development the haddock egg can not be 

 distinguished from that of the cod, hence the term "cod-haddock," and when 

 first spawned there is even danger of confusing them with the eggs of one of our 

 commonest flounders — the "witch" (p. 515), whose breeding season immediately 

 succeeds that of the haddock. The formation of black pigment, however, identifies 

 the cod-haddock egg as such (the embryonic pigment of the "witch" is yellow), 

 and shortly before hatching, when the embryo is as long as the circumference of the 

 yolk, the characteristic arrangement of the pigment granules marks it either 

 as cod or as haddock, as explained below (p. 444). 



io We base this statement on the fact that there were about as many eggs floating on the surface as at 10 to 15 or 40 meters at 

 the station where the experiment just mentioned was carried out, although artificially fertilized eggs sank in water dipped from 

 the surface. 



