292 



BULLETIN OF THE BUREAU OF FISHERIES 



forms, were very abundant at station 3, but totally absent elsewhere. A similar 

 variation was found in Massachusetts Bay eggs at various seasons. The average 

 size increased during the cold winter months and declined as the water warmed in 

 the spring. 



Table 14. — Cod eggs from Massachusetts Bay 



Date 



Dec. 11, 1924 

 Dec. 17, 1924 

 Jan. 7, 1925.. 

 Feb. 6, 1925.. 



Average 

 size of 50 



Millimeters 

 1.458 

 1.495 

 1.494 

 1. 529 



Date 



Average 

 size of 60 

 eggs 



Mar. 10, 1925 

 Apr. 8, 1925.. 

 May 20, 1925. 

 June 5, 1926.. 



Millimeters 

 1.501 

 1.613 

 1.488 



1.425 



Basing conclusions on these collections alone, it was natural to conclude that 

 temperature has a very decided effect on the size of cod eggs, causing them to average 

 larger during the colder periods and decrease in size as the water becomes warmer. 

 Thus, in Massachusetts Bay eggs averaged smallest in December and May and 

 largest in February. In the region of the Labrador current the largest average was 

 found at the northernmost station and the smallest at the more southerly ones, 

 where the summer warming of the water had become noticeable. 



In order to determine whether the variations are explainable on the basis of 

 temperature alone, experiments were carried on at Gloucester and on the Boars 

 Head fishing grounds in April, 1926. Eggs and sperm from two fish (Gadus callarias) 

 were fertilized in two jars of water, one maintained at 0° C. and the other at 8° C. 

 The water in both jars had been taken from the surface at one spot on the fishing 

 grounds. In general, the results appear significant, 50 eggs fertilized at 0° C. 

 averaging 1.447 millimeters (1.45, 1.44, 1.45, 1.44, and 1.45 millimeters averages in 

 groups of 10) and 50 at 8° C. averaging 1.4106 millimeters (1.41, 1.39, 1.41, 1.43, and 

 1.41 millimeters). The unfertilized eggs remaining at the bottom of the jars showed 

 the same relationship to temperature, but in each case the average size was somewhat 

 greater than in the developing eggs. 



Ehrenbaum found that in the North Sea cod eggs averaged 1.46 millimeters in 

 January and 1.30 millimeters in April. Fifty cod eggs from the Gloucester hatchery 

 averaged 1.497 millimeters on March 25, 1925; of these, 4 per cent were 1.35 milli- 

 meters; 14 per cent, 1.40 millimeters; 16 per cent, 1.45 millimeters; 38 per cent, 1.50 

 millimeters; 10 per cent, 1.55 millimeters; 14 per cent, 1.60 millimeters; and 4 per 

 cent, 1.65 millimeters. Welsh found that artificially fertilized eggs in the Gulf of 

 Maine averaged 1.46 millimeters, but no date is given. 



Where water temperatures are more or less even over large areas, cod eggs at 

 two or more spawning centers may average the same in size. In such cases it would 

 not be possible, of course, to make distinctions on the grounds themselves, and any 

 estimates would have to be based on the abundance of eggs traversing a known 

 course from one spawning center to another. 



