| CRD 02-01
Table 3. Impacts of Clam
Dredges on Benthic Habitat |
| TYPE OF IMPACT |
DEGREE OF IMPACT |
DURATION |
TYPE OF EVIDENCE |
COMMENTS |
| MUD |
| Removal of Major Physical Features |
N/A |
|
|
|
| Impacts to Biological Structure |
N/A |
|
|
|
| Impacts to Physical Structure |
N/A |
|
|
|
| Changes in Benthic Prey |
N/A |
|
|
|
| SAND |
| Removal of Major Physical Features |
Unknown |
|
|
|
| Impacts to Biological Structure |
XXX |
Months - Years1 |
PR, GL, PJ |
1 Dependent upon species composition
(eg. Amphipod tubes < 1 yr recovery) |
| Impacts to Physical Structure |
XXX2 |
Days - Months |
PR, GL, PJ |
2 Represents major alteration to regime
for soft bodied organisms |
| Changes in benthic prey |
Unknown |
|
|
|
| GRAVEL |
| Removal of Major Physical Features |
N/A |
|
|
|
| Impacts to Biological Structure |
N/A |
|
|
|
| Impacts to Physical Structure |
N/A |
|
|
|
| Changes in benthic prey |
N/A |
|
|
|
| KEY: X = Effect can be present, but is rarely
large; XX = Effect is present and moderate; XXX = Effect is often
present and can be large; N/A = Effect is not present or not
applicable; Unknown = effects are not currently known; (H) =
High energy environment; (L) = Low energy environment; PR = Peer
reviewed literature; GL = Grey literature; PJ = Professional
judgement. For definitions of Substrate Type and Type of Impact
see Appendix D.
NOTE: Ongoing Canadian studies for clam dredges are near
completion and will contribute substantially to this discussion. |