CREASERand CLIFFORD: LIFE HISTORY STUDIES OF SANDWORM 



plied by the dilution factor to obtain the final egg 

 count. 



Hydrographic data were usually obtained 

 shortly after the collection of worm samples. 

 Mean monthly water temperature was calcu- 

 lated from 25 thermister recordings collected in 

 situ at 30-min intervals at hydrographic stations 

 occupied for 12 h. Mud temperature records 

 were collected in situ by digging a shallow hole in 

 the mud flat and inserting a thermometer hori- 

 zontally at a depth of about 10 cm. Water sam- 

 ples used in salinity analysis were obtained using 

 a 1 1 water sampler. Water samples of 5 ml were 

 analyzed for salinity by the Knudsen method. 



Sandworms were captured during spawning 

 using scuba techniques or dip nets. 



RESULTS 



Salinity and Temperature of 

 the Study Area 



The salinity and temperature regime of the 

 river water at the study area during the period 

 November 1966-October 1967 is summarized in 

 Figure 1. During these studies, surface salinity 

 varied between 17 and 29%o, surface tempera- 

 ture between -1° and 15°C, bottom salinity be- 

 tween 24 and 29%o, and bottom temperature be- 

 tween -1° and 14°C. 



Length Frequency 



Preliminary digging in the Wiscasset closed 

 area indicated that sandworms were most abun- 

 dant in the region of the low-water mark. Within 

 this region, significant variations in both abun- 

 dance and size were recorded for three randomly 

 selected 1 m 2 plots dug from one tidal height 

 during one time period. Because of this variation, 

 digging more than 1 sample plot/mo was desir- 

 able. We elected to dig and combine the results of 

 3 randomly selected plots/mo because the com- 

 bined results produced fairly consistent length- 

 frequency trends between months. Considerable 

 breakage of all sizes of sandworms was encoun- 

 tered during handling and processing. During 

 agitation, the presence of sharp shells and debris 

 in the upper layer of organic ooze resulted in 

 additional breakage of juvenile sandworms 

 prevalent there. Some unavoidable bias has 

 therefore resulted in the numbers of juvenile 

 worms reported. Length-frequency results for 

 all whole worms collected during August, Sep- 



tember, and October are shown in Figure 2. 

 Sandworms captured varied in length between 

 <1 and 31 cm. Numbers of whole individuals 

 captured during these months varied between 

 546 and 701. Figure 2 indicates some recruit- 

 ment of small individuals into the sampled popu- 

 lation during the summer. Additional length-fre- 

 quency information collected during this study 

 is presented in Creaser and Clifford (1981) 6 . 



The August-October 1967 length-frequency 

 data, when combined to produce sufficient num- 

 ber, was analyzed by the method of Harding 

 (1949), as explained by Cassie( 1950), to determine 

 the number of assumed age modes. Although five 

 assumed modes and linear growth were detected 

 by this analysis, there is considerable overlap in 

 length at age; the results are therefore question- 

 able until they can be verified against other 

 aging techniques. 



6 Creaser, E. P., and D. A. Clifford. 1981. Life history 

 studies of the sandworm Nereis virens Sars, in the Sheepscot 

 Estuary, Maine. Maine Department Marine Resources Re- 

 search Laboratory, Res. Ref. Doc. 81/16. 37 p. 



N = 546 



AUG 1966 



10 15 20 25 



LENGTH, CM 



Figure 2.— Monthly length frequency distributions for three 

 combined plots dug from the Wiscasset closed area. 



737 



