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Fish Habitat Restoration
Historically, many tributaries within the Annapolis watershed have supported healthy, self-sustaining populations of native brook trout and Atlantic salmon. Due to habitat loss and degradation, many of these streams are now unable to sustain the number of fish they once produced.


Installation of a retaining wall
Land clearing is responsible for much of the damage done to the waterways. The removal of trees and vegetation along the banks of rivers and streams can have many negative impacts:
  • Increased bank erosion
  • Over-widening of the river, caused by bank erosion
  • Increased sediment loading in the waterway
  • Higher water temperatures
  • Poor nutrient cycling
  • Decrease in cover and habitat for aquatic and semi-aquatic species, including fish, amphibians, plants and insects
Fish habitat restoration is done to repair as much of the damage as is possible and mimic natural processes that would be found at an undisturbed site. Disturbance to the water body is minimized using many different methods, listed below.
  • Much of the work is done by hand, during low-flow conditions
  • Natural materials, preferably found on site, are used in the repair
  • Constructed restoration structures are designed to mend the stream in as natural a way as possible,
  • Constructed restoration structures are designed to require no long-term maintenance, as the stream will return to its natural patterns when the structures have done their job
The restored fish habitat is then of a quality more suitable to sustain natural populations of native fish species.

Improvement Techniques

The Fish Habitat Restoration Project is designed to rehabilitate degraded or impaired fish habitat and/or water quality. Low-impact stream enhancement tools include in-stream structures such as digger logs, deflectors and brush fences. Stream bank stabilization, riparian zone planting, and garbage clean up are other improvement techniques.

In-stream Restoration Structures

Digger Logs:

Digger logs are the primary structure used in the restoration of salmonid stream habitat in Nova Scotia. They consist of hardwood logs secured using rebar to the streambed, at a 30-degree angle to the bank. Boulders and cobble are removed from the downstream side of the log and placed upstream to create a ramp, causing the water to cascade over the log.

The purpose of these types of structures is to re-establish the natural meander of the stream, and to create pools and gravel beds for spawning. As the water cascades over the log, fine materials are removed, and the remaining gravel is sorted, thus creating desirable spawning habitat. These structures also help raise the oxygen content of the water, and the boulder and cobble ramp provides quality habitat for aquatic insects on which salmonids feed.

Wing Deflectors:

Wing deflectors are most commonly used in conjunction with digger logs. They are triangular rock structures whose bases are attached the bank, and pinnacles extend into the channel. Wing deflectors are often built with hardwood log frames and are secured to the streambed using rebar.

Their purpose is to deflect the flow in the desired direction, protect the bank from the erosive force of the flow, and to raise the water level by constricting the channel to its ideal width.

Retaining Walls:

Retaining walls are built against the stream bank, and are constructed of either logs or rock.

Their purpose is to hold bank materials in place where they are severely eroded and subject to failure. This allows for the re-establishment of vegetation, which will stabilize the bank, and prevents the influx of sediment into the stream.

Large Woody Debris Structures:

Large woody debris such as large logs or fallen trees play a major role in the formation of habitat characteristics that allow streams to support healthy fish population.

Logs and fallen trees can be anchored into place at strategic locations to perform a variety of tasks, ranging from stream bank protection to the creation of overhead cover for fish. Large woody debris also contributes to the creation of spawning beds and pools.
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