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



485 



These collections were made a few days before heaviest setting occurred in 1926, 

 and consequently the majority of the larva; were full grown and were retained by the 

 80 and 100 mesh screens. The greatest concentration of larvae in the hourly samples 

 was found at the time the tide changed from low slack water to flood, when an average 

 of 106 larvae per 200 gallons of water were collected. This finding is quite significant 

 in view of the fact that this is also the particular level or zone in which the heaviest 

 setting was observed to occur. In comparing the results of both quantitative methods 

 for the same days, we find that they are very similar and show that the largest num- 

 bers of oyster larvae are swimming in the water in Milford Harbor during the "low- 

 water period." In making the plankton collections from August 11 to 13, 1926, there 

 were no unusual meteorological conditions and the range of tide was approximately 

 6'}/2 feet, which is about equal to the mean daily range for this locality. _ 



Since a general scarcity of swimming larvae was found in the plankton collections, 

 the question naturally arises as to where the large numbers of larvae come from or 

 remain that later are found attached as spat in the same areas. Two possible ex- 

 planations of this phenomenon could be advanced: First, that the oyster larvae were 

 carried into the harbor by the flood tide from the sound, and second, that the larvae 

 were lying on the bottom during the greater part of the time. To investigate the first 

 possibility, it was necessary to determine (1) the horizontal distribution of the oyster 

 larvae during the low-water period and (2) the occurrence and abundance of the larvae 

 during the flood-tide interval at Stations Nos. 4, 5, and 6, which are located outside of 

 the harbor. 



In the following table, the horizontal distribution of the larvae during the period 

 of low water is shown for Milford Harbor and vicinity. In this series, made on July 

 25, 1925, the majority of the larvae were fully developed and were retained by the 80 

 and 100 screens. 



Table 16. — Horizontal dialrihution of larvse at low water on July 25, 19S5, for Milford Harbor and 



vicinity 



At Station No. 6, which is located in Long Island Sound 1 mile distant from 

 Milford Harbor, there is a large spawning bed, and here we find the larvae fairly 

 abundant at low water. At Station No. 5, which lies halfway between the harbor 

 spawning bed and that at Station No. 6, the oyster larvae were found to be virtually 

 absent not only in the series taken at low water, but also in the samples taken at all 

 stages of the tide during both summers. The larvae were found in greatest abundance 

 at Stations 2, 3, and 4 located close to the harbor spawning bed, which is the area 

 where later the heaviest setting occurred. In their horizontal distribution we find 



