(Groundfish of European shelf waters)

Assemblage data from 93 groundfish species, those that could be reliably sampled and identified in beam-trawl surveys by research vessels from several countries surrounding NW European shelf waters, were analysed by Rogers SI, Clarke KR, Reynolds JD 1999, J Anim Ecol 68: 769-782. The data matrix, C:\Examples v7\Europe groundfish\Groundfish density(.pri) is of 277 locations (ICES quarter-rectangles) sampled in the third quarter of the year over the period 1990-96, with the values being mean catch rates corrected to number of fish per 8m beam trawl per hour. The sites are divided a priori into 9 coastal areas (1 to 9 in factor area: 1=Bristol Channel, 2=Western Irish Sea, ..., 9=E Central North Sea, see the Edit>Properties box). Also available is a PRIMER format variable information file, the aggregation sheet, Groundfish taxonomy(.agg), met briefly at the end of Section 2. Open both into a new workspace and on Groundfish density Analyse>Resemblance> (Analyse between•Samples)&(Measure•Other: Gamma+>Taxonomy>(Type•Taxonomy)>Details >(Variable info. worksheet (taxonomic): Groundfish taxonomy)), accepting all defaults on this last dialog box – though you might like to take User specified>Weights to note how the step lengths between levels are set to be equal, resulting in path lengths between species of 0, 20, 40, 60, 80, 100, as earlier described. Alternatives might be to flatten the tree at the top, by setting the final step (Class) to 0, or to give more weight to the fine-level taxonomy, with decreasing entries 5, 4, 3, 2, 1.