face and bottom samples were taken by pump until June, and surface samples 

 from that time on were taken by bucket. Surface temperatures in Wickford 

 Harbor in 1951 are shown in table 1 and figure 2. 



Mya larvae. — Figure 5 and table 2 are a record of the occurrence of 

 My a larvae for 195l. ' A few straight-hinge larvae were present on the 

 first day of sampling. Not until the week of April 22, when the surface 

 water temperature was about 11° C, did an appreciable number of larvae 

 appear. From this date until the week of July 15, Mya larvae were in the 

 water each week, reaching a peak of abundance of 8,U00 straight-hinge 

 larvae per 35 gallons during the week of May 13 and nearly 500 late umbone 

 stage larvae per 35 gallons during the week of May 27. 



A small concentration of young larvae appeared in the latter part of 

 August and early September and a larger one appeared in October, resulting 

 in a few setting-stage larvae in early November. No other distinguishable 

 spawning waves were noted but occasional late umbone stage larvae were seen 

 in the samples well into early 1952. 



Venus larvae. — Abundance data for Venus larvae for 1951 are presented 

 in figure 6 and table 3. Larvae first appeared during the week of May 20, 

 when the surface water temperature was lU° to 15° C, increasing to a peak 

 of 2,h00 straight-hinge larvae per 35 gallons during the week of June 2iu 

 The abundance of young larvae then decreased to a level of approximately 

 100 per 35 gallons by mid-July, and no more young larvae were seen after 

 September 29. Late umbone stage larvae exceeding an abundance of 10 per 

 35 gallons were noted in only three weekly periods during the season. These 

 occurred between June 10 and July 10. The peak of abundance was approxi- 

 mately 70 per 3S gallons. As with Mya , occasional late umbone stage Venus 

 larvae were seen in the samples as late as February 8, 1952. 



Wickford Harbor, 1952 . 



Samoling began in Wickford harbor April 17 on a serniweekly schedule 

 and was discontinued after October 2, at which tine there were still a few 

 young Mya in the water but no Venus larvae. All samples were taken from 

 the same station as in previous years and only surface samples were 

 obtained. Surface temperatures in Wickford Harbor in 1952 are shown in 

 table 1 and figure 2. 



Mya larvae. — Figure 7 and table 2 show the abundance of Mya larvae in 

 Wickford Harbor in 1952. Straight-hinge larvae first appeared during the 

 week of April 27, when the surface water temperature was 10.5° to 11.0° C, 

 and late umbone stage larvae were in the samples a week later. The abun- 

 dance of young larvae was consistently low all during the spawning season 

 with one exception; during the latter part of Mav one weekly average of 

 1,600 per 35 gallons was attained. Otherwise, the weekly average for the 

 season was usually below 200 per 35 gallons. Lale umbone stage larvae were 



13 



