280 



BULLETIN OF THE BUREAU OF FISHERIES 



A line extending east from a point midway between stations 15 and 16 (about lati- 

 tudes 42° 10' N.) would divide these two branches. All bottles set out in the southern 

 part of this region turned south after leaving Massachusetts Bay and were recovered 

 either along the outer side of Cape Cod or at Nantucket. Stations 9 to 15, with the 

 inserted drift-bottle stations, are in this section. 



Bottles in the northern part turned to the east. This area includes stations 2, 

 16 to 19, and inserted drift-bottle stations between stations 16 and 19. 



RATE OP DRIFT IN FEBRUARY, 1925 



The bottle records also throw important light upon the rate of drift. Taken by 

 sections, the February records indicate that the average rate of drift in the southern 

 region was 1.5 nautical miles per day. This slow-moving drift about the inner arm of 

 Cape Cod represents a minor lateral branch of the main current. In the northern 

 region the average rate of the set leaving Massachusetts Bay, as shown by the two 

 bottles found drifting, was 4.4 miles per day. Bottle No. 74, set out in the northern 

 section, had taken the easterly course and averaged 5.4 miles per day for nine days. 

 Bottle No. 89, from the southern part of this region, drifted in the opposite direction 

 at a rate of 3.5 miles per day. Either these two branches later slackened their speed 

 considerably, the route was circuitous, or the bottles remained for some time before 

 being found, because the three that reached Nova Scotia show an average of only 1.36 

 miles per day and the two grounding at Nantucket, 0.62 mile per day. The average 

 drift out of Massachusetts Bay of approximately 4.5 miles per day agrees very well 

 with Mavor's (1922) records for 1919, when 11 bottles traveled from the Bay of Fundy 

 to Massachusetts Bay at an average rate of at least 4 miles per day. 



Applying the drift-bottle data to egg movements, it will be seen that the spawn- 

 ing grounds in Massachusetts Bay are included almost entirely in the northern region. 

 This suggests that the bulk of the eggs produced during the winter and early spring 

 would follow the course of the drift bottles directly out of the bay. Those taken along 

 the inner arm in Cape Cod Bay (figs. 7 and 12) probably represent the output of a 

 very small fraction of the grounds — the southern extremity. The drift-bottle experi- 

 ments, therefore, indicate that during the height of the season (January and Feb- 

 ruary) by far the greater part of the eggs produced on the Plymouth grounds do not 

 even circle the bay before entering the coastal waters but drift directly out at a rate 

 that may exceed 4 miles per day. 



DRIFT-BOTTLE RESULTS IN MAY 



By May, 1925, the general set in Massachusetts Bay had become considerably 

 altered (fig. 15). The increased amount of water entering from the Gulf of Maine 

 caused the direction of the set to change, so that, instead of turning west and following 

 around the shore line of the bay, it was forced directly across the entrance in a south- 

 erly direction. During the winter and early spring the entering current probably 

 circles around the inner margin of the bay. The general sweep of the drift in May is 

 clearly indicated by the movement of bottles from stations 18A and 32 (fig. 15). 

 In February these bottles would have been directly in the path of the easterly drift, 

 but now they were carried south to the tip of Cape Cod, where two grounded. A 

 third barely missed the cape and was found drifting 2 miles off Peaked Hill Bar. 



