1. Project Title: Metro Toronto Waterfront - Restoration of Natural Habitat Structure
At the time of writing, this habitat project is still in the planning phase. Funding is in place from three sources (Ontario Ministries of Natural Resources, and Environment and Energy, as well as Great Lakes Cleanup Fund). Implementation (placement of habitat structure) will occur during November, 1994.
2. Contact
Richard Strus
Metro Toronto RAP Biologist (alternate - Mark Heaton, Area Biologist)
Ontario Ministry of Natural Resources, Greater Toronto Area District, York South Area,
10401 Dufferin Street, P.O. Box 7400, Maple, Ontario L6A 1S9
Tel.: (905) 832-7169; FAX: (905) 832-7206
3. Agencies Involved
Metro Toronto and Region Remedial Action Plan
Ontario Ministry of Environment and Energy, 7 Overlea Blvd., 4th Floor,
Toronto, Ontario M4A 1AH
4. Restoration Goal
Increase structural complexity within sheltered Toronto waterfront habitats, thereby reducing the extent of aquatic habitat impairment caused by shoreline alteration.
5. Project Type
Placement of woody brush and fallen trees at sheltered warmwater sites, i.e., embayments and river mouths.
6. Background and Rationale
Aquatic habitats at the Metro Toronto waterfront have been degraded by physical alterations such as lakefilling, dredging, erosion control, and parks landscaping and maintenance. These activities have resulted in increasingly simplified littoral zones within the Toronto AOC. Addition of structure to relatively featureless warmwater habitats may increase fish production (Pardue 1973; Vogele and Rainwater 1975; Wege and Anderson 1979) and help restore natural productive capacity to the waterfront.
Sheltered warmwater habitats across the waterfront historically included wood debris deposited by river flow and shoreline erosion. Within the present urban setting, existing land and water uses (e.g., parks, marinas) may preclude larger-scale habitat restoration projects at some sites. Trees and brush continue to be cleared within the Toronto area for the purposes of urban development. Re-use of these materials may offer an inexpensive and feasible opportunity to improve habitat where natural structure is absent.
Placement of brush shelters and fallen trees at critical sites can provide cover for various biota, as well as attachment substrate for growth of periphyton and associated grazing organisms (invertebrates). Increased biological production at warmwater sites should result from greater structural complexity within existing littoral zones. Underwater woody structure may enhance spawning, nursery and feeding habitat for native fishes. Additional above-water habitat may be created for terrestrial and amphibious wildlife. Brush shelters have also been documented to improve colonization of aquatic vegetation at the placement site (Thomas and Bromley 1968).
Brush shelters and fallen trees will be located at sites defined by pre-project site assessment and fish community monitoring. Structure placement will be carried out during late fall, 1994.
7. Regulatory Considerations
This project followed the procedures for "Class Environmental Assesment For Small-Scale MNR Projects" as a Category "C" project having little or no detrimental effect on the environment. The environmental assessment for this project complied with the Environmental Assessment and Review Process Guidelines Order which sets out the Federal Environmental Assessment Review process. Authorization to proceed with the project was obtained from the Canadian Coast Guard, with compliance to requirements of navigation safety and the public right of navigation. The project was reviewed and endorsed by the Metro Toronto RAP coordinator representing the RAP Public Advisory Committee, as well as municipal representatives.
8. Criteria
Brush shelters and fallen trees will be located at sheltered sites tending towards warmwater conditions, and where cover and structure are lacking due to shoreline alteration. Depth of location will be defined by on-site conditions. Shallow placement with significant above-water structure may be carried out in turbid waters with high sedimentation rates. More transparent conditions may result in shelters being located at greater depth (3-5 m below minimum lake level). A minimum navigational depth of 2.4 m may be required near areas of boat activity. Initial structures will be deployed on an experimental basis and will be removable if necessary.
9. Project Design
Tree species selected to increase structural complexity of aquatic
habitat should provide long-
lasting underwater structure. Hardwood species such as maple,
oak, and beech are relatively durable under sheltered conditions
(Thomas et al. 1968). Cedar may also be used. Brush shelters will
consist of bundled units wired together and weighted to minimize
the possibility of dispersal by wave action. Brush bundles will
form units easily managed by two people. Large-diameter tree limbs
(diameter greater than 10 cm) will not be included in brush bundles/shelters
to minimize the possibility of any damage to boats. Fallen trees
will be chained to an appropriate anchor point at shore. Deeper
water brush shelters may perform a "reef" function and
be more extensively wired and weighted with concrete blocks. The
shelters will be linear in shape, run parallel to shore, and will
be located within the euphotic zone to allow periphyton to colonize
surfaces.
10. Implementation
Implementation of this project was completed during the winter of 1994/1995. Suitable trees and brush were obtained from various land clearing activities related to property development within the Metro Toronto area. On-site work consisted of placement of 55 weighted brush shelters (primarily white cedar) at the 3-m depth contour within a lake embayment of Humber Bay Park East. These were released from a boat at the appropriate depth.
Twenty-one fallen logs and tree crowns (white cedar and red pine) were placed between high and low lake water levels within a created coastal wetland at Colonel Samuel Smith Park. The logs and crowns were placed to provide available above-water and shallow-water structure at all lake level conditions. Tree crowns and logs were dragged over the ice to an appropriate anchor point, then left to settle to the wetland bottom during the spring thaw.
11. Degree of Environmental Intervention
Linear scale of brush shelter size will be in the order of several dozens of metres. No adverse environmental impacts are expected from this project, as woody materials exist naturally at sheltered littoral zones within the Great Lakes basin. These structures will not eliminate any existing habitat and are intended to restore natural complexity to shorelines previously degraded and simplified.
12. Cost
Projected cost of construction of two linear brush shelters during
the initial pilot year will
be 25 K.
13. Biological Assessment
Pre-project characterization at prospective sites consists of littoral habitat description and mapping, as well as evaluation of on-site fish communities and other biota. Similar post-project data collection will be carried out during 1995 and used to quantify "net gain" of productive capacity.
14. Measures of Success
Post-project indicators of increased productive capacity resulting from the created habitat include the following
increased levels of primary production (periphyton) occurring at the project site;
increased biomass of forage organisms (invertebrates) present on underwater structure;
increased numbers and biomass of forage fish occurring in the vicinity of the brush shelter;
increased numbers of young-of-the-year and juvenile sport fish present in the vicinity of the brush shelter;
improved colonization of macrophytes at the project site;
use of above-water brush structure by terrestrial and amphibious biota;
ability of the brush shelter to maintain structural and functional integrity for 15-25 years.
Success Rating: 1 (assessment incomplete).
15. Key References
Pardue, G.P. 1973. Production response of the bluegill sunfish, Lepomis macrochirus Rafinesque, to added attachment surface for fish-food organisms. Trans. Amer. Fish. Soc. 102: 622-626.
Thomas, P.M., and Bromley, D.D. 1968. The establishment of aquatic vegetation in and around artificial fish shelters in Douglas Lake, Michigan. Amer. Midl. Nat. 80(2): 550-554.
Thomas, P.M., LeGault, R.O., and Carpenter, G.F. 1968. Durability and efficiency of brush shelters installed in 1937 in Douglas Lake, Michigan. J. Wildl. Manage. 32(3): 515-520.
Vogele, L.E., and Rainwater, W.C. 1975. Use of brush shelters as cover by spawning black basses (Micropterus) in Bull Shoals Reservoir. Trans. Amer. Fish. Soc. 1975(2): 264-269.
Wege, J.G., and Anderson, R.O. 1979. Influence of artificial structures on largemouth bass and bluegills in small ponds. In D.L. Johnson and R.A. Stein [editors]. Response of fish to habitat structure in standing water. N. Cent. Div. Amer. Fish. Soc. Spec. Publ.6.
Correct citation for this contribution:
Strus, R. 1995. Metro Toronto Waterfront - restoration of natural habitat structure, p. 55-58. In J.R.M. Kelso and J.H. Hartig [editors]. Methods of modifying habitat to benefit the Great Lakes ecosystem. CISTI (Can. Inst. Sci. Tech. Inf.) Occas. Pap. No. 1.