The distribution of the invasive non-native gastropod Crepidula fornicata in the Milford Haven Waterway, its northernmost population along the west coast of Britain

Table 2 Distribution of Crepidula fornicata in the intertidal zone of the Milford Haven Waterway in South Wales, UK

	SS	SS/MS_total	df	p
Site	17,540.0	33.8	3	<0.001
Tidal height	24,980.6	48.2	2	<0.001
Site × tidal height	5525.9	10.7	6	0.100

		1.8 m	1.2 m
Mann–Whitney, factor tidal height	0.6 m	<0.001	0.001
Mann–Whitney, factor tidal height	1.2 m	<0.001

Results of nonparametric two-way crossed Scheirer–Ray–Hare test and Mann–Whitney pairwise comparisons to test for differences in C. fornicata densities between three tidal heights (0.6 m—0.5–0.7 m above Chart Datum; 1.2 m—1.0–1.3 m a. C.D. and 1.8 m—1.5–1.8 m a. C.D.) at four study sites (BR Beggars Reach, CO Cosheston, HA Hazelbeach, PE Pennar). Nonparametric tests were chosen due to heterogeneity in variances that could not be removed with data transformations. Significant differences are shown in bold

ISSN: 1438-3888