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Lotic-invertebrate Index for Flow Evaluation (LIFE) is a method for linking benthic macroinvertebrate data to prevailing flow regimes. This is an index designed for British Waters and is described in Extence & Balbi (1999). It may be calculated either at the family level or at the species level, and Species Diversity and Richness offers both options. Some taxa for which it is impossible to classify their flow preferences or where taxonomic issues make them unreliable do not score. The Pisces utility T-Group is useful for combining species data into higher taxonomic groups.

 

The index is calculated by assigning each taxa to one of 6 groups ranging from a group primarily associated with rapid flows to a group holding forms frequently associated with drying or drought impacted sites. Each taxa is then placed in a second category relating to its abundance. There are 5 abundance categories 1-9, 10-99, . , 10000+. These two values are then used to look up the score in a table. The final index is calculated as follows:

 

LIFE = Sum(fs)/n

 

where sum(fs) is the sum of the individual taxon flow scores for the whole sample, and n is the number of taxa used to calculate the sum(fs).

 

Higher flows should result in higher LIFE scores