49 



4.0 DISCUSSION 



Intertidal flats are important to the ecology and commercial fisheries of the New 

 England region. They produce substantial amounts of primary production in a form that is 

 immediately utilizable by consumer groups which in mm, provides forage for both 

 commercial fisheries species and migratory shorebirds (Peterson and Peterson, 1979; 

 Whitlach, 1982). In addition, intertidal flats support soft-clam and bait-worm fisheries 

 which are of direct importance to local economies (Brown, 1993). As with other coastal 

 resources, habitat loss or degradation of habitat function is a continuing concern. While 

 restoration or replacement of coastal habitats such as salt marshes has received 

 considerable attention over the years, the potential for construction of unvegetated 

 intertidal habitats has largely been ignored and the potential for beneficial use of dredged 

 material in construction of such habitats has remained relatively unexplored. 



Overall, the project has been a success. Initial concerns that erosion would degrade 

 the site appear to have been groundless. Although no topographic survey has been 

 conducted since construction of the flat to directly measure changes in size or shape, 

 repeated visual observation over nine years, including aerial photography, indicates that the 

 physical integrity of the site has not been compromised (Figure 1-2; Figure 1-3). The flat 

 still extends from the midpoint of the western side of Sheep Island to a small rocky outcrop 

 near the northern end of the island (Figure 1-2). It has retained a roughly triangular shape 

 at low tide and there is no physical evidence of erosion, e.g., no apparent decline in height 

 or maximum extent from the shoreline (personal observation). Sediment texture of the 

 constructed flat and reference areas has remained constant over time with the exception of 

 1994 when both sites had increased proportions of coarse materials (Figure 3-1). Sediment 

 organic content has always been highest at the constructed flat, a reflection of the finer 

 sediments present at this site, and although organic contents declined over time, the decline 

 was similar at both sites. 



The project was also successful in that populations of soft-clams ( M. arenaria ) and 

 clam- worms (N^ virens) were established at the constructed flat. Of the two species, 

 clearly the soft-clams were the most successful, with commercial-size clams ("50 mm) 

 being present as early as 1992 (Figure 3-7). The continuing presence of adult clams in 

 1998 (Appendix Table 1) and smaller clams throughout the study (Figure 3-5) indicate that 

 the soft-clam population is firmly established. Anecdotal evidence in the form of personal 

 observations of rakers on the flat in 1994 and the presence of numerous raking pits on the 

 flat's surface in 1998 are also indicative of a viable clam population. A clam- worm 

 population was also established at the constructed site. Small worms have been consistently 

 present throughout the smdy (Figure 3-8) and large worms were abundant in both 1991 and 

 1992. The absence of large worms in 1998 might seem to belie the conclusion that a clam- 



Ecological Monitoring of a Constructed Intertidal Flat at Jonesport, Maine 



