274 



BULLETIN OF THE BUREAU OF FISHERIES 



Were there no dominant drift, but only tides and winds, to scatter the eggs, 

 one would find newly spawned eggs and those in early cleavage stages over the 

 spawning grounds and over a large area a mixture of eggs and larvae in various 

 stages of development. Contrasted with a condition of this sort, in regions subjected 

 to a definite drift flowing in one direction, we should expect to find over the spawning 

 grounds only eggs in the earliest stages of development, provided there were no 

 other complicating influences, such as storms, tidal actions, or neighboring spawning 

 areas nearer the source of the drift. Following the course of the current from the 

 grounds, eggs should be found in progressively later stages of incubation, the dis- 

 tances traveled before hatching depending on two factors — temperature (as this in- 

 creases or retards the rate of development) and the rate of the drift. In localities 

 where a very rapid drift passes over the grounds the eggs might be carried great 

 distances before hatching, provided the temperature were low enough. For example, 

 eggs incubating in a temperature of 1° C. (February temperature in Massachusetts 

 Bay) and subjected to a drift of 4 miles a day might travel more than 120 miles 

 before hatching, and the fry then might drift for two to two and a half months. 

 Those fry might then seek the bottom 420 miles from the spawning grounds. This, 

 of course, is merely a hypothetical case, but it illustrates a possible occurrence. 

 Consequently it was expected that conditions in Massachusetts Bay would be com- 

 plicated, for tidal action and contrary winds, often of considerable force, might 

 prove in themselves ample cause for confusion, even though other spawning grounds 

 were not so located as to form an added disturbing influence. 



As previously stated, the Plymouth grounds could be established easily as the 

 principal production center for locally spawned eggs throughout the season. In 

 Figure 6 (based on the results of eight trips) the large percentages of eggs in early 

 cleavage stages found along the western shore from station 17 to station 8 indicate 

 clearly the source of production during the winter and early spring. By comparing 

 this figure with Figure 7 it will be seen that few late embryos remained along the 

 western shore, the movement being either south into the arm of Cape Cod (stations 

 5, 6, 7 and 8) or directly across the bay in an easterly direction (stations 3, 2, 18, 

 and 19). Drift-bottle experiments, which will be explained later, prove that both 

 movements were taking place. 



It was also interesting to find that, although storms apparently destroyed large 

 quantities of eggs (see p. 268), the general distribution was not altered seriously. 

 In spite of the particularly bad weather that had prevailed for several days before 

 the fourth trip, Figure 12 shows a concentration of embryos about the Province- 

 town region and of newly-spawned eggs over the breeding grounds. Probably when 

 the surface becomes disturbed the eggs tend to become distributed throughout the 

 water mass and thus escape being forced along by the wind, like objects that remain 

 at the surface. The distribution of stages during the fourth cruise was normal and 

 quite typical of conditions existing during the winter and early spring. 



The influence of haddock eggs first became noticeable on the eleventh cruise 

 (April 7-8), when a considerable increase in the average number of eggs taken in 

 Massachusetts Bay and also a noticeable change in the distribution of eggs in early 

 cleavage were observed. Figure 13, based on the distribution of cleavage stages, 

 shows for the first time large numbers of newly-spawned eggs in the outer parts of 

 the bay. In fact, at stations 31 to 33 all of the eggs taken were in early cleavage, 



