It took, on average, about 3 hours to sort the samples in this manner. Invertebrates were identified and enumerated at the lowest practical taxonomic level using existing keys and literature. Identification required I to 4 hours per sample, depending on the variety of animals present. Higher scores on BI reflect increasing organic loadings. These expected communities have b een calculated from collections made throughout southern Ontario.
Negative values indicate a significant difference from reference conditions.
This also partially standardizes PMA values and facilitates comparisons among physically different streams. Crayfish are common in Laurel Creek a nd its tributaries, and were collected at 9 sites. There was a strong correlation between the numbers of individuals identified and numbers of taxa. This suggests that if more indiv iduals were sorted and identified from any given sample, the number of taxa found there would increase. This is true to some extent, but we stopped sorting at about 200 animals only if no obviously new kinds were being found.