Fact Sheets - Fish Habitat Enhancement at CTC Gagetown

Aim

The fish habitat enhancement project at Combat Training Centre (CTC) Gagetown combines sustainable, realistic military training with responsible environmental stewardship in military training areas.

Introduction

The cool clear running waters of New Brunswick's rivers and streams have generated rich cultural heritage based on recreational and food fisheries. The province's Atlantic salmon and brook trout stocks are part of that heritage.

Through the years, the negative impact of the military training was more and more evident on the different streams of CTC Gagetown. The degraded state of the Nerepis River was of special concern to the environmental stewards at Gagetown. The river has been used by nearby residents for many generations, making it that much more important to restore.

A joint project by CTC Gagetown and the Department of Fisheries and Oceans was initiated in 1996 to gradually restore the river and streams at Gagetown to their natural state. The main objective of the project was to restore the existing fish habitats - particularly those favoured by Atlantic salmon and brook trout - in the watersheds at Gagetown, while allowing for sustainable military training.

Facts

Fish habitats

Atlantic salmon and brook trout both spawn in fresh water. Atlantic salmon spend their first two or three years in freshwater, then go out to sea for an additional one to four years. Salmon then return to the streams/rivers in which they were born and lay their eggs in gravel riffles in the fall. Brook trout prefer colder water than salmon (15° C vs. 19° C). Trout require clean gravel riffles or sandy underwater springs for spawning. Trout can spend their life cycle entirely in freshwater but some of them overwinter in estuaries and return in the spring (“sea run” trout).

Issues and challenges

Military vehicles crossing streams in the CTC's General Manoeuvre Area (GMA) have often disturbed the natural habitat of Atlantic salmon and brook trout. Of particular concern was the release of large amounts of sediment at the many high-traffic stream crossings. Road infrastructures within the training area were also identified as a major contributor to the sedimentation problem.

Sediment can affect aquatic life directly by killing fish, either through gill irritation or by killing insect population which is an important food source. Sediment can also affect fish habitats indirectly though the deposition of fines onto the stream's substrate. The latter can infill pools, cause gravel beds to become unusable for spawning, and cause the stream to erode its banks.

Alteration of water parameters is another important threat to the living of fish. Water temperature changes as small as one degree have been known to cause substantial changes in the home range of some species. High water temperatures lead to low dissolved oxygen values and make it difficult for fish to survive. The stream temperatures may remain high due to a lack of vegetative cover and water depth and to stream widening, caused by sedimentation.

Plan - Phase I

The first phase of the pilot project to restore stream habitat was a comprehensive survey of the majority of the streams at Gagetown. This phase of the plan focuses mainly on the Sucker Brook watershed at the southern end of the training area.

Sucker Brook is part of the larger Nerepis River Watershed, which has been heavily impacted by military training, especially in Gagetown's GMA. The system has a native Atlantic salmon run, but the numbers have been found to be very low. Since 1996, Sucker Brook has benefited from the installation of digger logs, side channel blocking, the removal of debris piles and stream bank stabilization. The work has allowed pools to form, creating ideal fish spawning habitats. The channel has also been deepened and a more natural stream pattern has emerged. Similar work in one form or another has also been completed on numerous other streams that criss-cross the training area.

To further reduce the harmful effects of realistic military training on fish habitat outside the GMA, a hardened ford/approach restoration project was initiated in 1997. This ongoing project was design to reduce river sedimentation at the high traffic fords throughout the training area. The project consists of digging out the streambed and its approaches, and then putting down large rip-rap or pieces of broken rock as a wear surface. This prevents rutting and track scour during wet periods and significantly reduces the amount of sediment that migrates into the streams.

To help control the second major cause of sedimentation, steps have been taken to improve roadway infrastructure maintenance. Culverts are now designed to meet 100-year flood capacity and are constructed using techniques and precautions specifically designed to protect fish habitat.

Plan - Phase II

The second phase of the project - water monitoring - began in 1998 with the purchase of instream dataloggers. These state-of-the-art instruments measure temperature, conductivity, pH, dissolved oxygen, turbidity and depth. The baseline information is used to determine the effects of training around the streams, particularly those brought on by precipitation. Turbidity, caused by suspended solids, has been found to be high in many of the streams, but most notably those that receive water from the GMA. In addition to instream monitoring of water quality variables through the use of dataloggers, water temperature is continually monitored in streams throughout the training area since 1997. The sensors measure the water's temperature every hour from mid-May to mid-October, making it possible to discern patterns or changes.

It was found that water temperatures during the summer of 1998 were generally cooler than the previous year, despite the warmer weather. This was encouraging because salmon prefer cooler water, which generally contains more oxygen. This is also an indication of the positive effects of shading on the streams, even after a short period of time.

In 1998, 10 rock sills - large rock boulders dug into the river bottom at angles much like a digger log - were installed in two strategic locations in the river. These structures cause the river to scour pools, create riffle habitat, and redefine the channel's pattern by narrowing its width.

Results

The transient nature of Atlantic salmon and brook trout makes it hard for officials to determine whether the improvements have helped to increase the number of fish returning to their natural spawning habitat. However, water quality monitoring and annual fish population studies show the changes are positive. The results of sediment remediation efforts have had a favorable effect and are expected to greatly aid in the restoration of the Nerepis River and the other streams at Gagetown.

Conclusion

The ongoing hardened ford/approaches restoration project, combined with the closing of fords and the use of specially designed culverts, has significantly reduced the harmful alteration of fish habitats outside the GMA due to military activities. Through the above initiatives, the stream crossings at CTC Gagetown can be returned to a state where salmon and trout will thrive.

Download a PDF version of this file (1,084 kb - Adobe PDF file)

Download a copy of the Adobe PDF Reader. Please note that this is an outside link.