Module 4 Stream Invertebrate Survey Interpretation
Toquaht River, May 30, 2022 | Survey ID: 255
A) ABUNDANCE AND DENSITY
ABUNDANCE total number of organisms from Column B: 45
DENSITY invertebrate density per square meter
# of 30cm x 30cm samples: 3
(total # counted 45) / (# of 30cm x 30cm samples x.09m2 3 / (Area: 0.27)) : 166.67
B) PREDOMINANT TAXON: Blackfly Larva, (20)
C) WATER QUALITY ASSESSMENTS
POLLUTION TOLERANT INDEX
Good Acceptable Marginal Poor
greater than 22 22 - 17 17 -11 less than 11
3 x (# of category 1) = 6
2 x (# of category 2) = 0
(# of category 3) = 4
Pollution Tolerant Index = 10
EPT INDEX
Good Acceptable Marginal Poor
greater than 8 5 - 8 2 - 5 0 - 2
Total number of EPT taxa from Column C = 2
EPT TO TOTAL RATIO
Good Acceptable Marginal Poor
0.75 - 1.00 0.50 - 0.75 0.25 - 0.50 0 - 0.25
# of EPT 8 / total 45 = 0.18
D) DIVERSITY ASSESSMENT
Total Number of Taxa: 6
PREDOMINANT TAXON RATIO
Good Acceptable Marginal Poor
0 - 0.40 0.40 - 0.60 0.60 - 0.80 0.80 - 1.0
PREDOMINANT TAXON RATIO:
20 / 45 = 0.4444
SITE ASSESMENT RATING
Good Acceptable Marginal Poor
4 3 2 1
Pollution Tolerance Index: 1
EPT Index: 2
EPT to Total Ratio: 1
Predominant Taxon Ratio: 3
Total: 1.75

Field Data as Collected
Polution Tolerance
Number Counted
Number of Taxa
Common Name
Category 1 - Polution Intolerant 3 1 Caddisfly
0 0 Dobsonfly
0 0 Gilled Snail
5 1 Mayfly
0 0 Riffle Beetle
0 0 Stonefly
0 0 Water Penny
Sub Total: 8 2
Category 2 - Somewhat Pollution Tolerant0 0 Alderfly larva
0 0 Aquatic Beetle
0 0 Aquatic Sowbug
0 0 Clam, Mussel
0 0 Cranefly Larva
0 0 Crayfish
0 0 Damselfy Larva
0 0 Dragonfly Larva
0 0 Fishfly Larva
0 0 Scud
0 0 Watersnipe Larva
Sub Total: 0 0
Category 3 - Pollution Tolerant 10 1 Aquatic Worm
20 1 Blackfly Larva
0 0 Leech
5 1 Midge Larva (chironomid)
0 0 Planarian
0 0 Pouch Snail
0 0 Truebug Adult
2 1 Water Mite
Sub Total: 37 4