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Pierrepont Farm
wildlife monitoring report, September 2013

Freshwater macroinvertibrate survey in the farm pond

by Bill Young

A freshwater macroinvertebrate survey was carried out in the farm pond, using standard FBA (Freshwater Biological Association) pond nets. Finds were identified as far as possible to species level and numbers of each were recorded in order to calculate a diversity index.

Family Genus Species Number N n(n-1)
Nepidae Ranatra linearis 2 2
Anax Imperator (early Instar) 4 12
Cloeon dipterum 6 30
Lestes sponsa 1 0
Limnea stagnalis 4 12
Caleopteryx splendens 1 0
Platicnemmis pennipes 4 12
Succinia putris 3 6
Planorbis planorbis 4 12
Notonecta glauca 2 3
Hydrachnella sp 2 3
Broad-bodied or Four-spotted Chaser nymphs 3 6
Total N 36 Σn(n-1) 96

Simpson’s Index of Diversity, D, = Σn(n-1)/N(N-1)
D = 96/1260 = 0.076

Using Simpson’s Reciprocal Index of Diversity, 1/D, Reciprocal Index 1/0.076 &061; 13.1

Given the number of species recorded, this is very diverse.

Also seen were Common darter adult dragonflies, both male and female, and adult male Common Blue damselflies.

The farm pond should be surveyed annually at the same time for freshwater invertebrates, in order to determine its diversity.