were, in fact, a "composite" of an entire panel. The same sampling scheme was used for each of the three 

 trawl-lines. 



Shipworm infestation was assumed to be minimal in panels exposed from November to May. Hence, 

 all 15 panels were radiographed using the X-ray method described earlier, and if shipworms were present, 

 they were removed and identified. 



DATA ANALYSIS 



Data analyses consisted of comparisons between sites using observations made on panel sections 

 paired by their location in the panel. This type of pairing was necessary, because shipworm recruitment 

 rates vary with the location of the panel section observed (e.g., shipworm infestation is greatest on the 

 bottom and top ends of a panel). Parametric t-tests and non-parametric Wilcoxon 2-sample tests were 

 used to compare the occurrences of Teredo navalis between pairs of sites. 



RESULTS 



A total of 18 panels were collected in November 1985, after a six month exposure at distances of 100, 

 500 and 1000 m from the Millstone Quarry. Over 1500 shipworms were removed and identified from 

 these panels (Table 6). The estimated total recruitment of shipworms was 615 per panel at 100 m, 526 at 

 500 m and 388 at 1000 m. Teredo bartschi were collected only in panels at 100 m, and they represented 

 2.3% of the total number of shipworms which were collected at that distance. However, one of the 14 

 individuals collected was brooding pediveligers, indicating that T. bartschi can reproduce outside the quarry. 



Both parametric and non-parametric statistical comparisons were made concerning the abundances of 

 shipworms by panel section and distance. None of the three comparisons among the sites were significant 

 at a = 0.05. However, there is a trend of decreasing abundance with increasing distance from the quarry 

 (Table 7). Lx)W number of observations and high degree of intra-site (within site) variability contribute 

 to the lack of statistical significance; more data may substantiate a distinct trend. 



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