38 



David L. Penrose, David R. Lenat, K. W. Eagleson 



LU 



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1978 1979 



MONTH/YEAR 

 Fig. 5. Average number of organisms per sample, Cherryfield (CF-l) and 

 Morgan Mill (MM-l) creeks, February 1978-December 1979. 



Species (or taxa) Level Information 



Table 7 lists all benthic macroinvertebrates collected in the Upper 

 French Broad River Basin, and includes 267 taxa, derived from identifi- 

 cation of 81,000 organisms. Data on frequency and seasonal distribu- 

 tion are included. Frequency data are based on the number of times 

 each taxon was collected rather than on any quantitative measure of 

 abundance. 



Table 7 also lists the "months of maximum abundance." Since this 

 is a highly qualitative procedure, the analysis was very cautious. When 

 no clear seasonal pattern was apparent this column was left blank. It 

 was also left blank for all rare taxa. 



Life History Data. — Many taxa were found to have two or three 

 distinct seasonal peaks in abundance. In many cases, these peaks may 

 correspond to separate generations. Multiple peaks in abundance were 

 recorded for Ephemeroptera (12 taxa), Trichoptera (4 taxa) and Diptera 

 (15 taxa). Most of these taxa are grazers or filter-feeders. Since this 

 group of organisms included many classified as "abundant", a large 

 proportion of the benthos would be expected to have two or three gen- 

 erations per year. 



