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Third national assessment

Appendix B: Effect Indicators, Critical Effects Sizes and Studies Conducted

Table B1. Fish population effect indicators and endpoints for different study designs
Fish Population Effect IndicatorsFish Population Effect Endpoints
Lethal sampling designNon-lethal sampling designAlternative
Age frequency distribution
Length frequency distributionLength frequency analysis
(energy use)
Body weight-at-ageWeight of young-of-the-year (YOY) (age 0) at end of growth period
Length of YOY (age 0) at end of growth period
Whole animal wet weight
Shell length and width
Soft tissue fresh weight
(energy use)
Gonad weight-at-body weightRelative abundance of YOY (% composition of YOY)Gonad weight-at-body weight (gonadosomatic index [GSI])
Body Condition
(energy storage)
Body weight-at-lengthBody weight-at-lengthWeight (whole animal dry weight, dry shell or soft tissue) related to shell length
Liver Condition
(energy storage)
Liver weight-at-body weight  

*Alternative monitoring monitoring designs are described in the Metal Mining Technical Guidance for EEM (Environment Canada 2012a).

Table B2. Fish Habitat Effect Indicators:

  • Total density (number of animals per unit area)
  • Evenness index (distribution of numbers of individuals among types of organisms)
  • Taxon richness (number of different types of organisms)
  • Similarity index (resemblance in invertebrate community structure between exposed and reference areasFootnote 21)
Table B3. Critical effect sizes (CESs)
Fish Effect EndpointsCESBenthic Invertebrate Effect EndpointsCES
Body weight-at-length± 10%Total density± 2SD
Relative liver weight± 25%Taxon richness± 2SD
Relative gonad weight± 25%Evenness index± 2SD
Weight-at-age± 25%Similarity index (Bray-Curtis)≥2SD
Age± 25%  

Note: Differences in fish population effect endpoints are expressed as percent (%) of reference mean, while differences in benthic invertebrate effect endpoints are expressed as multiples of within-reference-area standard deviations (SDs).

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Table B4. Number and design of biological monitoring studies conducted or attempted by mines (number of mines conducting studies in parentheses)

Fish Habitat
Biological Monitoring Study Design1st Study*2nd Study3rd Study4th StudyTotal Studies Conducted
Control Impact and Multiple C/I109 (114)73 (77)27 (28)4 (4)213
 Gradient3 (3)2 (2)005
Reference Condition Approach1 (3)1 (3)002
Magnitude and Geographic Extent**  11 (13)3 (3)14
Investigation of Cause  10 (13)21 (25)31
Fish population **
Biological Monitoring Study Design1st Study*2nd Study3rd Study4th StudyTotal Studies Conducted
Lethal (only)66 (69)36 (38)17 (17)3 (3)122
Non-lethal (only)24 (24)17 (17)5 (5)0 (0)46
Lethal and non-lethal12 (14)17 (19)5 (6)2 (2)36
Alternative4 (5)5 (7)2 (2)0 (0)11
Magnitude and Geographic Extent  9 (11)2 (2)11
Investigation of Cause  7 (7)16 (18)23
Use of fisheries resources
Biological Monitoring Study Design1st Study*2nd Study3rd Study4th StudyTotal Studies Conducted
Fish tissue30 (30)25 (26)11 (12)1 (1)67

Note: some studies were conducted jointly by two or more mines;
* includes five mines considered to have completed the first study twice (two had a change in the location of the final discharge point, one had an important change in water treatment and two had to relaunch the assessment of effects as the reference and exposure areas sampled in the previous studies differed in terms of habitat type).
** Seven mines were not required to assess the fish component in at least one biological monitoring study because the proportion of effluent in the receiving environment was lower than 1% at a distance of 250 metres from the final discharge point.

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