19 



From these data and the abundance results it appears that a substantial set 

 (recruitment) of soft-clams occurred soon after construction of the flat. Analysis of the 

 core abundances, a measure of small-sized animals, suggests that recruitment was and 

 continues to be equally successful at both sites. The abundance of larger-size animals, 

 collected by rake and pit sampling, indicates that large animals were evenly distributed 

 among the sites at first, but became substantially more abundant on the constructed flat 

 than the reference area (Table 3-1). The trend for mcreasing length of animals from the 

 constructed flat (Figures 3-7 and 3-8; Appendix Table 1) indicates that individuals rapidly 

 grew to commercial length ("50 mm). The numerous raking pits evident on the flat during 

 the 1998 field sampling (personal observation) is perhaps the clearest, if anecdotal, 

 evidence for establishment of a commercially viable population. 



3.2.1.2 Clam-worms ( Nereis virens) 



Survey results for Sheep Island clam-worm populations are similar to those for soft- 

 clams (Table 3-3; Table 3-4). Abundances from rake and pit samples reflected considerable 

 annual variation with twice as many animals present at the reference area than the 

 constructed flat in 1991, the opposite result in 1992, and no animals found at either site in 

 1998 (Table 3-3). Clam- worms are large-bodied, mobile animals which periodically leave 

 their burrows to swim and breed in the water column (Pettibone, 1963). It is unclear how 

 much of the variation in rake/pit abundances was due to reproductive behaviors, namral 

 interaimual variations in abundance, site-specific differences, or other factors. Data for 

 small-sized animals, i.e. the core data, indicate no difference (p>0.05) in abundance 

 between sites or between sites over time (Table 3-4). Differences among years were 

 restricted to the highest and lowest values with 1990 abundances being the least and 1998 

 being the highest (Figure 3-8). Size frequency analysis, limited to the 1991 and 1992 data, 

 indicates that while the 1991 constructed flat and reference area populations had similar 

 structures (Figure 3-9), in 1992 constructed flat populations were dominated by much 

 smaller animals than those found at the reference area (Figure 3-10). 



Table 3-3. Sheep Island Clam-worm ( Nereis virens ) Survey Results* 

 Year DM n REF n 



1990 



















1991 



16.7 



19 



33.3 



40 



1992 



27.8 



213 



4.1 



37 



1998 



















Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine 



