1. Project Title: Rehabilitation of the Native Aurora Trout Lakes
2. Contact
Ed Snucins or John Gunn
Co-operative Freshwater Ecology Unit, Ontario Ministry of Natural Resources, Dept. of Biology, Laurentian University, Sudbury, Ontario P3E 2C6
Tel.: (705) 675-1151; FAX (705) 675-4859; E-mail: JGUNN@Nicel.Laurentian.Ca
3. Agencies Involved
Ontario Ministry of Natural Resources
Ontario Ministry of the Environment and Energy
Laurentian University
and support through the World Wildlife Fund
4. Restoration Goal
To improve the water quality in one of the native aurora trout (Salvelinus timagamiensis) lakes and reestablish a reproducing population of aurora trout.
5. Project Type
Amelioration of lake acidity by treatment with powdered limestone.
6. Background and Rationale
The aurora trout is a unique genetic stock of the brook trout that is distinguished by its colouration. Its entire range consists of only two small lakes (Whirligig and Whitepine) located about 100 km north of Sudbury, Ontario. Acidification of the lakes by atmospheric deposition of pollutants resulted in the extirpation of the aurora trout from its range during the 1960's. The aurora trout was saved from extinction by a captive breeding program that began in 1958 and in 1987 it was placed on the Canadian endangered species list.
During the 1980's, natural water quality recovery was occurring
in many lakes in the Sudbury area following reductions in local
metal smelter emission levels, but the aurora trout lakes were
slow to respond and their acidic water quality continued to be
limiting for aurora trout survival. By the late 1980's, numerous
attempts to establish reproducing populations of aurora trout
in other lakes where the population was not indigenous had failed
and there was growing concern about the adverse effects of prolonged
domestication on the fitness of the stock. Therefore, if the acidification
problem could be eliminated, the best chance of quickly reestablishing
a self-sustaining wild population would be in Whirligig and Whitepine
lakes. Whole-lake liming, a proven technique for temporarily ameliorating
lake acidity and increasing brook trout survival (Gloss et al.
1989), was done in Whirligig Lake and aurora trout were re-introduced
following the treatment.
7. Regulatory Considerations
a) Generally, an Environmental Assessment permit from the Ministry of Natural Resources (MNR) District office would be required; however, this was waived because the project involved reintroduction of a native fish stock.
b) Permission from the MNR Temagami District was required for
the use of aircraft and boats/motors on Whirligig and Whitepine
lakes because they are located in a
Provincial Preserve.
8. Criteria
A minimum pH of 5.0 is required for aurora trout reproduction. However, increasing lake pH to 6.5 would provide suitable water quality (pH > 5.0) for a number of years even if gradual reacidification occurred.
9. Project Design
Whirligig Lake and its headwater, Little Whitepine Lake, were both treated in 1989 with powdered calcite to achieve a post-liming pH of 6.5 and an alkalinity of 2.0-3.5 mg/L in each lake. Whirligig Lake became reacidified and was treated again in 1993.
10. Implementation
The neutralizing material was powdered calcite (mean diameter 5 µm, 96% CaCO3). The application rate was calculated using a PC-compatible version of the "Deacid" model developed by Harold Sverdrup in Sweden for the U.S. Acid Precipitation Mitigation Program (Sverdrup and Warfvinge 1985). The model calculates the calcite dose needed to achieve user-defined end points from starting chemical conditions. Model input variables include the following: lake surface area, volume, water residence time, pH, Ca, DOC, and alkalinity.
The material was transported to the lakes by helicopter from the nearest road, a distance of about 10 km. In 1989, 21 tonnes of calcite were spread manually by emptying bags of the material into the propeller wash of a boat. This treatment succeeded in raising the pH of both lakes to 6.5. Adult and juvenile aurora trout were released into Whirligig Lake in 1990.
Whirligig Lake gradually reacidified and in 1993 it was treated with 6 tonnes of calcite. This time the material was applied by releasing it from a bag suspended below a helicopter. An additional 3 tonnes of calcite were stored on shore for future use, if necessary.
11. Degree of Environmental Intervention
There were no negative effects.
12. Cost
1989 1993
Labour and materials $7 200 $4 100
Aircraft $9 000 $2 200
Total $16 200 $6 300
($771/tonne) ($700/tonne)
Biological Assessment ~ $2 500/yr
Monitoring will be continued for one more year (1995) and then
possibly be cut back to every
5 years.
13. Biological Assessment
The water quality (pH, alkalinity, conductivity, metals, nutrients, ions, Al speciation) of the treated lakes is monitored each year at monthly intervals throughout the ice-free period. Biotic community (macrobenthos, phytoplankton, zooplankton) species composition and abundance are also determined annually.
Schnabel mark-recapture estimates of aurora trout population abundance are obtained each year during the fall spawning season. Fish growth, diet, spawning site characteristics and reproductive success are also monitored.
14. Measures of Success
Successful reproduction by the introduced aurora trout has occurred every year. Individual fish growth is comparable to historical values in the native lakes and by 1991 the biomass of aurora trout had increased to levels typical of healthy brook trout populations in unacidified lakes.
Success Rating: 4
Continued survival of the aurora trout in Whirligig Lake depends on maintaining water quality. It is hoped that the legislated 1994 Sudbury metal smelter emission reductions will be sufficient to delay or possibly even prevent reacidification. Water quality monitoring will continue and the lake will be treated again if necessary.
Whitepine Lake, the other lake where aurora trout were native, is located downstream from Whirligig Lake and its water quality has also improved (pH 5.2 in 1994). Aurora trout were reintroduced to Whitepine Lake in 1994.
15. Key References
Gloss, S.P., Schofield, C.L., Spateholts, R.L., and Plonski, B.A. 1989. Survival, growth, reproduction, and diet of brook trout (Salvelinus fontinalis) stocked into lakes after liming to mitigate acidity. Can. J. Fish. Aquat. Sci. 46: 277-286.
Sverdrup, H., and Warfvinge, P. 1985. A reacidification model for acidified lakes neutralized with calcite. Water Resour. Res. 21: 1374-80.
Correct citation for this contribution:
Snucins, E., and Gunn, J. 1995. Rehabilitation of the native aurora trout lakes, p. 17-20. 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.