CAIN: REPRODUCTION AND RECRUITMENT OF RANGIA CUNEATA 



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JASON 



Figure 13.-Nuinber of Rangia set and salinity at station Dg from July 1970 to January 1972. 



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FiGURE 14.-Number of Rangia set and salinity at station Cg from July 1970 to January 1972. 



Table 2.-Average number of Rangia set (per collector) at both 

 deep and shallow stations by season. 



by early October 1970. This was the highest 

 number collected at any time or place during the 

 study. No set was collected at stations C or Cs from 

 late March to late December 1971. The fall setting 

 was very small with only 5 collected at station C 

 and 18 at station Cs during December 1971 and 

 January 1972. 



Rangia set ranged in length from 230 to 500 /^m, 

 but averaged about 300 ju,m. Larger individuals 

 were generally collected at the shallow stations 

 but may have been members of an earlier set 

 washed in by wave action. 



The setting patterns of the other bivalves are 

 presented in Figure 15. Station A received more 

 set of all three species than the other stations 



because of its proximity to their adult populations. 

 Brachidontes recurvus and Macoma mitchelli 

 were collected farther upriver than M. balthica. 

 The first two species were common at stations A, 

 B, and D. Brachidontes recurvus and M. mitchelli 

 are evidently more tolerant of low salinities as 

 they were the only set found during the low 

 salinity conditions of fall 1971. All three species 

 have a nearly year long spawning season with 

 minor spring peaks and a major peak in the fall. 



The three most common organisms found on the 

 bottles were Rhithropanopeus harrisii, 

 Callinectes sapidus, and the blenny, Chasmodes 

 bosquianus. These three potential set predators 

 were typically found at stations A, B, and D during 

 the fall and winter months. During high salinity 

 periods, R. harrisii was found at station C. 



Hydrographic Data 



Freshwater input levels were usually high in 

 late winter and spring, declining to low levels in 

 late summer and fall (Figure 16). Flow during the 



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