Home: Publications: Fact Sheet Series: Fish habitat & dredging
 horeline
areas provide habitat for a variety of aquatic organisms including fish.
The nearshore area is where many fish species lay their eggs, feed and
seek protection from predators. Changes or disruptions to these areas
can threaten their survival. If you own or lease waterfront property,
you can help protect the fish populations in your lake or river by
protecting fish habitat along your shoreline.
Dredging is the removal or displacement of any material from the bottom of a lake or stream.
It can harmfully alter, disrupt or destroy the areas in which fish live, feed and reproduce and
can also result in the re-suspension of contaminants affecting water quality.
Before deciding to dredge, consider the cost of the project, the cost of maintenance and
whether alternatives to dredging exist. For example, could you drive your boat around obstacles
such as shoals, stumps or rocks, or could you use an offshore mooring or swimming raft? If you
decide to dredge, you will need to take special care to preserve fish habitat. The scale of the
dredging project, its location, and the manner in which the activity is carried out will determine
if it may be harmful to fish and fish habitat.
Be aware of the Fisheries Act and other legislation
The federal Fisheries Act provides for the protection of fish
habitat. Under this Act, no one may carry out any work or undertaking
that results in the harmful alteration, disruption or destruction of fish
habitat (HADD), unless authorized by the Minister of Fisheries and Oceans
Canada. The Act also states that no one is permitted to deposit a deleterious
(harmful) substance into water containing fish. Violations to the Fisheries
Act can result in substantial fines, and/or the risk of imprisonment.
If found guilty, then the violator may also be required to cover the costs
of restoring the habitat at the site and/or be required to fulfill other
court ordered remedies. Other legislation that may be relevant to building
a dock, boathouse or boat launch is outlined in the introductory Fact
Sheet: What you should know about Fish Habitat.
Contacts and approvals
If your project involves dredging, the table on the next page will help
you to determine which agency you should contact. In some instances, you
may have to contact more than one agency. Keep in mind that approval from
one government agency does not guarantee that you will be able to obtain
approval from another agency.
Remember you must obtain all approvals before starting work. Early consultation
can save you from designing a dredging project that will not be approved.
Information you will need to submit
When seeking approvals or permits you will need to submit the following information:
- Your name, address, telephone number, and if available, a fax number and e-mail address
- Rationale for the dredging project
- Waterbody name and location including the lot and concession numbers, county, township,
municipality, and if known, latitude and longitude
- Proof of ownership for each of the properties where the work will be done and the most
recent legal survey(s)
- Detailed description of the work site including a signed and dated map or sketch with
dimensions indicating the location and distances to the average annual high-water mark
of existing buildings, shoreline structures and property lines
- Plan view (top down) sketch or drawing of the total area to be dredged showing existing
shoreline length (m), proposed works and the distances to the average annual high-water
mark. If you are doing this work in conjunction with your neighbour(s), your sketch should
show the combined works
- Cross-sectional (side view) drawing (with dimensions) of proposed structures, indicating
the current water level and distances to the average annual high-water mark
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- Description of the type of substrate being dredged indicating approximate
percentages of sand, silt, clay, rock, gravel and aquatic vegetation, etc.
- Description of how and where the dredged material will be stabilized/disposed
- Proposed date(s) of dredging and the type of equipment to be used
- Description of type of aquatic plants, if any, to be removed
- Description of any measures to be used to avoid harmful impacts
to fish and fish habitat during the dredging project
- Information on previous dredging at the site (e.g. date last dredged,
area dredged, approvals for past dredging)
- Information you have about fish use of the site
- Indicate if the material to be dredged has a history suggesting it might be contaminated
- Photographs of the work site and surrounding shoreline
- Description of any proposed use of explosives
- Other agencies contacted.
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A site visit by agency staff may be necessary before your proposal can be approved.
Best practices
The following practices are intended to prevent or minimize any potential harmful impacts
to fish and fish habitat that may result from your project:
Dredging methods:
Both manual and mechanical methods can be used during dredging operations. Preferred
methods are those that minimize disturbance to the bottom and contain any sediment
that is stirred-up.
How much to remove:
Try to minimize the size and depth of the area to be dredged. Generally, those types of
projects that pose a high risk to fish habitat will require approval.
Boat channels:
Dredging for a single boat channel should be no wider than six metres. A boat channel
can be shared among adjacent property owners. For safety reasons, shared or community
boat channels need to be wider than single channels. In most cases, community channels
should not exceed eight metres in width.
Disposal of the dredged material:
If the dredged materials are fine-grained (e.g. sand, silt, clay), then
they must be disposed of well above the average annual high-water mark
and outside any regulated flood plain area. Dredged material must be suitably
stabilized to prevent it from washing back into the water. If allowed
to enter the water, the fine-grained materials could blanket and suffocate
sensitive fish habitat. Once the materials are suspended in the water,
they can affect water quality as well as polluting or clogging nearby
water intakes. A preferred option is to cover the trench or dredged area
with clean and coarse material (e.g. gravel, cobble, rocks or boulders).
If the dredged material is coarse (e.g. clean gravel, rocks and boulders),
it is preferred from a fish habitat perspective to return the material back into
the water. When placing materials back into the water, avoid navigational
hazards by placing the material in water of equal or greater depth than it
came from. This material is to be free of fine-grained materials and not to
be placed in a wetland. Approval from a provincial regulatory authority(ies)
will be required if materials are being placed back in the water.
When contamination is suspected:
If the site has a history suggesting that the sediments to be dredged have the
potential to be contaminated, consult with your local provincial regulatory authority(ies)
to find out if chemical testing will be required.
Rocks and woody material:
Rocks, stumps, logs and woody material provide good fish habitat and should not be
removed from the water. If any materials need to be temporarily removed, they should
be stockpiled and replaced to where they came from, or to an adjacent area of similar
water depth.
Timing is critical:
In-water dredging activity should not occur during local fish spawning and nursery periods
since it could disturb spawning behaviour, smother eggs and kill young fish. Contact your
local provincial regulatory authority(ies) for details on the timing of your project.
Maintain or preserve shoreline vegetation:
Shrubs and trees growing adjacent to lakes and streams are important.
This vegetation provides overhead cover for fish, shade to minimize warming
of the water and a source of food for fish (e.g. insects fall off the
vegetation into the water). Nearshore vegetation also provides benefits
to wildlife in the form of nesting sites, cover from predators, etc.
The removal of some vegetation adjacent to the waterbody may be
necessary to allow for equipment access. Following completion of the
project, all areas should be stabilized to prevent erosion and re-vegetated
as soon as possible.
Avoid areas with aquatic plants:
Aquatic plants play an important role in the ecology of shoreline areas. If you
cannot avoid dredging in these areas, you may need additional approvals. For
more information, see Fact Sheet I-2: Fish Habitat &
Controlling Aquatic Plants.
Avoid spawning and nursery areas:
If you suspect your property is adjacent to a fish spawning or nursery site, you
are strongly advised to talk to agency staff before you dredge. Fish species may
have only one spawning/nursery site in a waterbody and any in-water activity near
these sites will result in a HADD.
Protect water quality:
A sediment or silt screen should be installed around the entire work area
prior to starting your dredging project. After the work is completed and
the sediment has settled on the lake bottom, the screen should be carefully
removed. Dredging should only occur on calm days. This will help to prevent
the suspension of fine sediment particles into the water column and will
ensure the silt screen is not disturbed by wave action. Sediment or silt
screens should be inspected daily and maintained to prevent the spread
of suspended sediments to adjacent water. Be aware, you may be required
to continue monitoring the site once the work is completed to ensure there
is no spread of suspended sediments.
Working together to protect fish habitat
Help maintain the quality and quantity of fish habitat in our lakes and streams.
For more advice on how to construct an environmentally friendly dock, boathouse,
or boat launch, contact your local agency staff directly.
Contact information - Ontario
| If the dredging proposal. . . |
Your first contact should be. . . |
| is in the Rideau Canal or Trent-Severn Waterway |
Parks Canada Agency (PCA) |
| is in a federally owned small craft harbour |
DFO - Small Craft Harbours |
| is on public (Crown) land or a private water lot |
Your local Conservation Authority (CA). Where there is no designated CA,
contact your local Ontario Ministry of Natural Resources (OMNR) office. |
| may affect boat navigation |
DFO - Canadian Coast Guard |
| involves the use of explosives in or near water |
DFO - Ontario/Great Lakes Area |
| is a maintenance dredge and is on public (Crown) land or a private water lot |
Contact your local OMNR office |
| is within a regulated floodplain |
Contact your local CA |
| For details on the timing of your project, contact your local OMNR office. |
Other Working Around Water Fact Sheets:
What you should know about Fish Habitat
C-1 Fish Habitat & Docks, Boathouses and Boat Launches
C-2 Fish Habitat & Building a Beach
C-3 Fish Habitat & Building Materials
C-4 Fish Habitat & Shoreline Stabilization
C-5 Fish Habitat & Constructing Ponds
I-1 Fish Habitat & Dredging
I-2 Fish Habitat & Controlling Aquatic Plants
I-3 Fish Habitat & Sunken Log Retrieval
I-4 Fish Habitat & Stream Cleanup
L-1 Obtaining a Fisheries Act Authorization
L-2 Municipal Drains in the Southern Ontario Region
T-1 Fish Habitat and the Effects of Silt and Sediment
T-2 Fish Habitat & Fluctuating Water Levels on the Great Lakes
www.dfo-mpo.gc.ca/canwaters-eauxcan
Cette publication est également disponible en français.
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