INVESTIGATION OF OYSTER SPAWNING, ETC., MILFORD, CONN. 467 



2. Seventy per cent of the recovered bottles were collected during the first 

 month, 13 per cent during the second month, and the remainder about equally 

 divided over the next eight months. 



3. The bottles recovered during the first month were distributed as follows: 

 76.7 per cent to the Connecticut shore, 5.3 per cent at the entrance or outside of the 

 Soimd, and 18 per cent on the Long Island shore. 



4. On the Connecticut shore the bottles were recovered from the Norwalk 

 Islands to Goshen Point, a distance of 65 miles, 15 of which were to the west of the 

 points of release and 50 to the east. 



5. In the region at the entrance of the Sound and outside, only 12 bottles were 

 recovered. 



6. On the Long Island shore, bottles were recovered from Oldfield Point to 

 Orient Point, a distance of 45 miles. 



7. The greatest distance covered by a drift bottle was approximately 150 miles. 



8. The fastest recorded di'ifts were 45 miles in 9 days and 80 miles in 15 days, 

 which give average drifts of 5 and 5.3 miles per day, respectively. 



9. A greater percentage of bottles was recovered from the groups released at 

 low water, or with- the flood tide, than from those released during the ebb tide. 



10. The recovery of the bottles, in relation to time and position, showed a clock- 

 wise distribution along the shores of the Sound. 



The general movement of the water in Long Island Sound is primarily tidal, 

 resulting in a dominant clockwise circulation, as represented in Figure 24. The rate 

 of movement, as indicated by the drift-bottle records, is approximately 5 nautical 

 miles per day. The existence of such a circulation is of great importance in pro- 

 ducing favorable conditions for the growth and propagation of oysters in Connecticut 

 waters. The water coming from the harbors and estuaries on the last of ebb tide is 

 of much lower salinity than that in the Somid and in the spring and summer is con- 

 siderably warmer. Instead of being carried out to the ocean, it meets the tidal 

 current in the Sound, which has already changed to flood, and is carried to the west- 

 ward and then spread to the north over the vast oyster region, creating conditions 

 that are favorable for growth and propagation of oysters. In the dumping of mud, 

 sludge, or other refuse, even in the designated areas in the Sound, strict attention 

 must be paid to the stage of tide or the material is liable to be carried and deposited 

 on the oyster grounds and beaches. In all cases dumping should be done preferably 

 at the time of high water in the Sound or during the first 2-hour run of the ebb 

 current. This suggestion is made at this time in view of the recent heavy mortality 

 of oysters that occurred on the beds off Bridgeport as the result of dumping mud 

 from the harbor. 



SALINITY 



The sahnity of the water in Long Island Sound and its estuaries and harbors is 

 determined by two main factors — namely, the discharge of fresh water by the rivers 

 and the inflow of salt water from the ocean. In the Sound the salinity is highest 

 and decreases gradually as we approach the sources of fresh water along the shore. 

 We have a typical example in Figure 25, in which the general distribution of salinity 

 is shown for Milford Harbor and vicinity. The figures are based on the average of 



