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Appendix II. Identification of mussel species most at risk in the lower Great Lakes drainage basin, based on evidence of decline in the study area.
| Species | Species
Number* | Before 1960
# occurrences | Before 1960
% of records | Before 1960
% of sites | After 1960
# of occurrences | After 1960
% of records | Direction of
change** | After 1960
% of sites** | Direction of
change** | Risk
category*** |
|---|
| Alasmidonta undulata | 37 | 3 | 0.22 | 0.44 | 1 | 0.04 | - | 0.13 | - | 1 |
| Elliptio complanata | 3 | 83 | 6.07 | 12.22 | 83 | 3.01 | - | 10.41 | - | 1 |
| Epioblasma o. perobliqua | 41 | 1 | 0.07 | 0 | 0 | - | - | - | - | 1 |
| Epioblasma t. rangiana | 35 | 5 | 0.37 | 0.74 | 4 | 0.15 | - | 0.50 | - | 1 |
| Epioblasma triquetra | 26 | 14 | 1.02 | 2.06 | 13 | 0.47 | - | 1.63 | - | 1 |
| Ligumia nasuta | 5 | 71 | 5.19 | 10.46 | 67 | 2.43 | - | 8.40 | - | 1 |
| Obovaria olivaria | 32 | 10 | 0.73 | 1.47 | 1 | 0.04 | - | 0.13 | - | 1 |
| Pyganodon cataracta | 24 | 16 | 1.17 | 2.36 | 4 | 0.15 | - | 0.50 | - | 1 |
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| Species | Species
Number* | Before 1960
# occurrences | Before 1960
% of records | Before 1960
% of sites | After 1960
# of occurrences | After 1960
% of records | Direction of
change** | After 1960
% of sites** | Direction of
change** | Risk
category*** |
|---|
| Lampsilis siliquiodea | 1 | 194 | 14.18 | 28.57 | 238 | 8.64 | - | 29.86 | = | 2 |
| Pleurobema coccineum | 17 | 28 | 2.05 | 4.12 | 35 | 1.27 | - | 4.39 | = | 2 |
| Simpsonaias ambigua | 38 | 2 | 0.15 | 0.29 | 2 | 0.07 | - | 0.25 | = | 2 |
| Truncilla donaciformis | 29 | 13 | 0.95 | 1.91 | 18 | 0.65 | - | 2.26 | = | 2 |
| Villosa fabalis | 34 | 6 | 0.44 | 0.88 | 7 | 0.25 | - | 0.88 | = | 2 |
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| Species | Species
Number* | Before 1960
# occurrences | Before 1960
% of records | Before 1960
% of sites | After 1960
# of occurrences | After 1960
% of records | Direction of
change** | After 1960
% of sites** | Direction of
change** | Risk
category*** |
|---|
| Lampsilis r. radiata | 9 | 56 | 4.09 | 8.25 | 86 | 3.12 | - | 10.80 | + | 3 |
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| Species | Species
Number* | Before 1960
# occurrences | Before 1960
% of records | Before 1960
% of sites | After 1960
# of occurrences | After 1960
% of records | Direction of
change** | After 1960
% of sites** | Direction of
change** | Risk
category*** |
|---|
| Alasmidonta viridis | 16 | 30 | 2.19 | 4.42 | 72 | 2.61 | = | 9.03 | + | 4 |
| Anodontoides ferussacianus | 14 | 36 | 2.63 | 5.30 | 71 | 2.58 | = | 8.91 | + | 4 |
| Fusconaia flava | 11 | 47 | 3.44 | 6.92 | 99 | 3.59 | = | 12.42 | + | 4 |
| Lampsilis fasciola | 33 | 7 | 0.51 | 1.03 | 14 | 0.51 | = | 1.76 | + | 4 |
| Lampsilis ovata | 6 | 69 | 5.04 | 10.16 | 121 | 4.39 | = | 15.19 | + | 4 |
| Lasmigona costata | 7 | 65 | 4.75 | 9.57 | 129 | 4.68 | = | 16.19 | + | 4 |
| Leptodea fragilis | 4 | 77 | 5.63 | 11.34 | 131 | 4.76 | = | 16.44 | + | 4 |
| Ligumia recta | 12 | 42 | 3.07 | 6.19 | 78 | 2.83 | = | 9.79 | + | 4 |
| Potamilus alatus | 8 | 57 | 4.17 | 8.39 | 102 | 3.70 | = | 12.80 | + | 4 |
| Quadrula quadrula | 20 | 21 | 1.54 | 3.09 | 46 | 1.67 | = | 5.77 | + | 4 |
| Obliquaria reflexa | 31 | 10 | 0.73 | 1.47 | 22 | 0.80 | = | 2.76 | + | 4 |
| Utterbackia imbecillis | 36 | 5 | 0.37 | 0.74 | 9 | 0.33 | = | 1.13 | + | 4 |
| Villosa iris | 18 | 28 | 2.05 | 4.12 | 54 | 1.96 | = | 6.78 | + | 4 |
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| Species | Species
Number* | Before 1960
# occurrences | Before 1960
% of records | Before 1960
% of sites | After 1960
# of occurrences | After 1960
% of records | Direction of
change** | After 1960
% of sites** | Direction of
change** | Risk
category*** |
|---|
| Actinonaias ligamentina | 21 | 20 | 1.46 | 2.95 | 58 | 2.11 | + | 7.28 | + | 5 |
| Alasmidonta marginata | 23 | 16 | 1.17 | 2.36 | 68 | 2.47 | + | 8.53 | + | 5 |
| Amblema p. plicata | 13 | 41 | 3.00 | 6.04 | 113 | 4.10 | + | 14.18 | + | 5 |
| Cyclonaias tuberculata | 30 | 10 | 0.73 | 1.47 | 40 | 1.45 | + | 5.02 | + | 5 |
| Elliptio dilatata | 10 | 54 | 3.95 | 7.95 | 131 | 4.76 | + | 16.44 | + | 5 |
| Lasmigona c. complanata | 40 | 1 | 0.07 | 0.15 | 58 | 2.11 | + | 7.28 | + | 5 |
| Lasmigona compressa | 15 | 34 | 2.49 | 5.01 | 108 | 3.92 | + | 13.55 | + | 5 |
| Obovaria subrotunda | 28 | 13 | 0.95 | 1.91 | 32 | 1.16 | + | 4.02 | + | 5 |
| Ptychobranchus fasciolaris | 22 | 17 | 1.24 | 2.50 | 47 | 1.71 | + | 5.90 | + | 5 |
| Pyganodon grandis | 2 | 111 | 8.11 | 16.35 | 355 | 12.89 | + | 44.54 | + | 5 |
| Quadrula p. pustulosa | 25 | 16 | 1.17 | 2.36 | 40 | 1.45 | + | 5.02 | + | 5 |
| Strophitus undulatus | 19 | 24 | 1.75 | 3.53 | 134 | 4.87 | + | 16.81 | + | 5 |
| Toxolasma parvus | 39 | 2 | 0.15 | 0.29 | 7 | 0.25 | + | 0.88 | + | 5 |
| Truncilla truncata | 27 | 14 | 1.02 | 2.06 | 56 | 2.03 | + | 7.03 | + | 5 |
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| Total # records | | 1369 | | | 2754 | | | | | |
| Total # sites | | 679 | | | 797 | | | | | |
*for reference to Fig. 2.
**a "+" sign indicates a significant increase and a "-" sign indicates a significant decrease in the species over time; a 20% difference is considered significant.
***category 1 is most at risk and category 5 is least at risk.
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