FISHERY BULLETIN: VOL. 73, NO. 2 



Figure 2.-The distribution of Rangia 

 cuneata in the James River, Va. Seg- 

 ments are at 5-nautical mile intervals. 



2 wk, but bad weather and boat failures oc- 

 casionally delayed this to 3 wk. Beginning 22 Sep- 

 tember 1970 collections at station C commenced. 

 Collections at all stations were terminated in 

 January 1972. 



In the laboratory these clams were measured, 

 weighed, shucked, and the gonads dissected out 

 and placed in a solution of alcohol. Formalin,^ and 

 acetic acid (AFA) for fixation. Gonad tissues were 

 sectioned at 7-10 /xm with a rotary microtome, 

 stained with Delafield's hematoxylin, and coun- 

 terstained with eosin. Gonad tissue stage of 

 development was determined following the 

 scheme of Ropes (1968) who categorized the 

 seasonal gametogenic cycle of Spisula solidissima 

 as: early active, late active, mature, partially 

 spawned, or spent. Similar stages of development 

 were first described by Ropes and Stickney (1965) 

 for Mya arenaria and have subsequently been 

 used for two other members of the family Mac- 

 tridae; Mulinia lateralis (Calabrese 1970), and 

 Tresus capax (Machell and De Martini 1971). The 

 number of clams in each category, regardless of 

 their sex, was recorded for each sample. 



The sex ratio of clams from each station was 

 calculated and a chi-square test used to establish 

 goodness of fit to a 1:1 ratio. 



During June 1970, clams collected at stations A 

 and B were placed in four groups (5-10, 11-20, 

 21-30, and 41-50 mm). These clams were sectioned 

 and stained to determine the size at which they 

 contain reproductive products. 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



Set Collectors 



Collectors used to determine the time and in- 

 tensity of setting were placed at stations A, B, C, 

 and D and inshore from these areas in shallow, 

 sandy areas (Figure 1). These stations were 

 designated as As, Bs, Cs, and Ds. Stations A, As, B, 

 Bs, and Ds were examined from June 1970 and C, 

 Cs, and D from September 1970, at approximately 

 2-wk intervals until January 1972. 



The set collector was a plastic gallon jar with an 

 8.7 cm diameter mouth. The mouth was covered 

 with a plastic 5 mm mesh to prevent the entry of 

 predators. The jar rested on the bottom, fastened 

 to a concrete block. 



Water flowed across the mouth of the jar and 

 suspended sediments, detritus, and me- 

 tamorphosing clams settled to the bottom. In the 

 field, the contents of the jar were washed through 

 a 0.174 mm mesh screen. In the laboratory each 

 sample was elutriated to remove most of the de- 

 tritus (Cofl^n and Welch 1964). The material 

 remaining after elutriation was examined for 

 clams under a dissecting microscope. All bivalves 

 were counted and some were measured. Set of 

 bivalve species other than Rangia was also iden- 

 tified and counted. 



Environmental Data 



Water samples for salinity, dissolved oxygen, 

 and temperature measurements were taken 

 whenever biological collections were made. A 

 Kemmerer bottle was used to obtain bottom water 

 samples at the deep stations. Samples at shallow 



414 



