|Lat / Long||54.5833333, -112.6166667|
|Max depth||60 m|
|Mean depth||15.5 m|
|Dr. Basin Area||234 km2|
|Drainage Basin||Beaver River Basin|
|Sport Fish||Walleye, Yellow Perch, Northern Pike, Lake Whitefish|
|TP x||North: 38South: 40 µg/L|
|CHLORO x||North:14.0South: 16.0 µg/L|
|TDS x||North: 221South: 220 mg/L|
Amisk is a beautiful recreational lake, nestled within a mixed forest in the County of Athabasca in central Alberta. It is 175 km northeast of the city of Edmonton and 15 km east of the village of Boyle, south of Secondary Road 663 (FIGURE 1). The lake is long and narrow, with a main axis that runs north-south. It has two distinct deep basins: the larger south basin is 60-m deep and the north basin is 34-m deep. The lake derived its name from the local abundance of beaver, or amisk in Cree, and the inflow and outflow rivers of the same name (Chipeniuk 1975; Holmgren and Holmgren 1976).
In the early 1940s, a mink farm and a resort were established on the northwest shore of the lake. The mink were fed fish from the lake. The resort had boat and cabin rentals (Chipeniuk 1975; Boyle Dist. Hist. Soc. 1982). Over the years, these developments were replaced by two subdivisions, and a trailer park was also built at the north end of the lake. One of the subdivisions, Pelican Beach, takes its name from the large flocks of pelicans that previously frequented the lake (Boyle Dist. Hist. Soc. 1982). The majority of the shoreline is undeveloped.
Fishing, boating and swimming are popular on Amisk Lake. A public boat launch, Kitty's Landing, and a day-use area on the northwest side are operated by the County of Athabasca (FIGURE 2). The sport fishery includes yellow perch, northern pike and walleye. In 1988, a long-term aeration program was begun to enhance sport fish habitat in Amisk Lake. The lake and all inlet streams are closed to fishing for a seven-week period in spring (Alta. For. Ld. Wild. 1989). There are no boating regulations specific to Amisk Lake, but general federal regulations apply (Alta. For. Ld. Wild. 1988). Moderate algal blooms develop in midsummer in Amisk Lake. The lake is surrounded by trembling aspen, willow, and clumps of white spruce and jack pine. Waterfowl and shorebirds are abundant, especially in the shallow bays.
Amisk Lake lies at the western edge of the Beaver River drainage basin. Skeleton Lake drains into the lake from the west. The Long Lake outflow, which is the headwaters of the Amisk River (Chipeniuk 1975), enters at the south end. Water from Amisk Lake flows over a small control structure at the north end into the Amisk River which flows east to the Beaver River (FIGURE 1).
About 88% of the drainage basin of Amisk Lake is forested; the dominant trees are trembling aspen, balsam poplar and jack pine (TABLE 1). There are two moderate-sized lakes in the drainage basin: Skeleton Lake to the northwest and Long Lake to the southwest. Muskeg areas are scattered throughout the drainage basin along with many temporary ponds and small lakes. The terrain is generally gently rolling to rolling, but the land rises steeply from the banks of the lake in places (Alta. For. Ld. Wild. n.d.).
Agricultural development is limited to only 4% of the drainage basin. There are gas wells on both sides of the lake and a large gravel pit to the northwest. Most of the land surrounding the lake is Crown land and is undeveloped, but there are two moderate-sized cottage subdivisions on the west side of the north basin (Amisk Lake Estates and Pelican Beach), a third subdivision just west of the lake (Baywin Estates) and a large trailer camp (Amisk Lake Trailer Park) at the north end of the lake.
Several small streams together with two larger streams - one from Long Lake and the other from Skeleton Lake - flow into Amisk Lake. These streams are dotted with beaver dams, and flow is intermittent.
Amisk Lake is long (8 km) and relatively narrow (on average 0.6 km wide). The depth of the north basin is similar to that of many of the deeper lakes in central Alberta (mean depth of 10.7 m), whereas the depth of the south basin (mean depth of 19.4 m) is greater than most (TABLE 2). The lake bed drops steeply from the shore, particularly in the central part of the south basin (FIGURE 2).
There are extensive beds of rooted macrophytes in the shallow areas at both ends of the lake and in sheltered coves. The near-shore area of the lake has a sandy substrate. The littoral zone extends to a depth of 4 m (Chambers and Prepas 1988) and covers an area of about 1 km2 (FIGURE 3).
A rock-filled timber weir was built at the Amisk Lake outflow in 1949 by Ducks Unlimited (Canada). The weir is now covered by a gravel pad and is not monitored (Alta. Envir. n.d.[b]). It has deteriorated overtime, and has been used as a road. The lake level has been relatively constant over the period of record, which began in 1969 (FIGURE 4). The maximum (612.02 m) and minimum (611.50 m) water levels were both recorded in 1986.
The water quality in Amisk Lake was studied intensively by the University of Alberta from 1980 through 1989 (Prepas et al. n.d.; Prepas 1983[a]; 1983[b]; Prepas and Trew 1983; Babin 1984; Prepas and Vickery 1984[a]; 1984[b]; Babin and Prepas 1985; Prepas and Trimbee 1988). Amisk Lake provides an ideal opportunity to evaluate the processes controlling productivity in a deep, naturally eutrophic lake.
Major ions in the surface waters of Amisk Lake are similar in both basins, and to those of many freshwater lakes in Alberta. The water is well buffered, and calcium and bicarbonate are the dominant ions (TABLE 3). The surface water is slightly coloured-recorded values have varied from 10 to 20 mg/L Pt (TABLE 3). Colour in Amisk Lake water increases when runoff from the drainage basin increases (Chambers and Prepas 1988).
Both basins are thermally stratified in summer, as illustrated in Figure 5 with data from 1982. The epilimnion extends to 5 m and the thermocline extends to 10 to 15 m. The hypolimnia are cool; the deep water in the south basin is as much as 2°C cooler than in the north basin. Over the eight summers the lake was studied, the maximum surface temperature recorded was 24°C.
Mixing in spring and fall was incomplete in both basins (FIGURE 5, 6). Consequently, dissolved oxygen concentrations were always well below saturation in the deeper waters. In addition, dissolved oxygen consumption rates were very high in the hypolimnia both in summer (in 1980, 0.691 and 0.628 g/m2 per day) and under ice in winter (in 1982/83, 0.848 and 0.554 g/m2 per day, south and north basins, respectively). Thus, at certain periods such as late summer and late winter, more than half the water in the north basin and three-quarters of the water in the south basin was completely anoxic (FIGURE 6). Few macro-organisms can survive extended periods in anoxic water.
In June 1988, a program to aerate the lake with pure oxygen was begun in the north basin of Amisk Lake. The goal of this program is to enhance sport fish habitat by keeping dissolved oxygen concentrations above 2 mg/L throughout the water column year-round. Over the first year, oxygen injection rates varied between 0.3 and 0.9 tonnes per day (Prepas et al. 1989). The project, which has been supported by Alberta Forestry, Lands and Wildlife, Environment Canada and a private company, is intended to continue for a minimum of 10 years. The effect of this treatment on water quality, the plankton, macroinvertebrates and sport fishery is being carefully monitored.
Phosphorus returns from the sediments to the open water at high rates (in 1982, 8.0 and 6.2 mg/m2 per day TP, south and north basins, respectively) whenever the dissolved oxygen concentration drops below 3 mg/L. Because these low oxygen conditions exist for long periods, total phosphorus concentrations in the deeper waters often are high; average hypolimnetic and under-ice concentrations frequently reach 150 µg/L. Total phosphorus concentrations are elevated in surface waters during the minimal mixing in spring and thermocline erosion in late summer and fall. Spring total phosphorus concentrations in the surface waters are quite variable. This year-to-year variation probably reflects the extent of winter ice cover and mixing during spring. Higher total phosphorus concentrations in the euphotic zone in 1982 relative to 1987 (TABLE 4) indicate differences primarily in spring total phosphorus concentrations. Summer total phosphorus concentrations varied between 26 and 40 µg/L over 7 years, from 1980 through 1987 (TABLE 5). In summer, a small amount (0.05 mg/m2 per day) of total phosphorus is transported across the thermocline. In contrast, more phosphorus is likely released from the shallower bottom sediments (Shaw and Prepas 1989). Extremely low total iron concentrations in Amisk Lake (TABLE 4) probably enhance the bioavailability of phosphorus, which first accumulates over the sediments and then is mixed into the surface waters (Nürnberg and Peters 1984).
Phytoplankton biomass (as estimated by chlorophyll a) usually follows changes in surface water phosphorus concentrations (FIGURE 7). Phytoplankton in Amisk Lake are phosphorus-limited most of the time; that is, biologically available phosphorus concentrations are low relative to concentrations of other essential nutrients. Summer chlorophyll a concentrations are more variable than total phosphorus concentrations in Amisk Lake. Over the 7 years illustrated in TABLE 5, average summer chlorophyll a concentrations ranged from 9 to 25 µg/L. These annual differences likely reflect yearly variation in spring water temperatures.
Total phosphorus and chlorophyll a concentrations in Amisk Lake are indicative of a eutrophic lake (TABLE 4). This level of productivity is directly responsible for a substantial portion of the oxygen depletion in deeper water and under ice. High algal biomass is also responsible for a euphotic zone that is relatively shallow (less than 6 m) for such a deep lake. Inorganic nitrogen levels are low, and the ratios of total nitrogen to total phosphorus in summer are high (33 to 54 in 1981, 1982 and 1985). Data collected from Amisk and other lakes indicate that most of the nitrogen does not come from external loading; rather, it is a result of nitrogen fixation by blue-green algae (Prepas et al. n.d.; Prepas and Trimbee 1988).
The phytoplankton of Amisk Lake was studied during the University of Alberta water quality study (Prepas et al. n.d.). In 1984, the dominant phytoplankton groups in Amisk Lake were diatoms (Bacillariophyta) and cryptomonads (Cryptophyta) in spring, and blue-green algae (Cyanophyta) such as Aphanizomenon flos-aquae and Anabaena circinalis and dinoflagellates (Pyrrhophyta) in summer (TABLE 6). Blue-green algae are prominent in this lake because of transport of phosphorus-rich water from the hypolimnion (Trimbee and Prepas 1987), particularly during spring and autumn mixing. Macrophytes have not been studied, but Richardson pondweed (Potamogeton richardsonii), large-sheath pondweed (P. vaginatus) and northern watermilfoil (Myriophyllum exalbescens) were widespread during 1988. The macroalga Chara sp. is abundant in a few areas of the lake.
Crustacean zooplankton were sampled by University of Alberta researchers in 1981, 1982 and 1984 (Prepas et al. n.d.; Prepas 1983[a]; Prepas and Vickery 1984[a]). In spring 1984, the dominant zooplankton in the top 6 m were copepods such as Acanthocyclops vernalis and Mesocyclops edax. In May and June, the small cladoceran Bosmina longirostris and the larger cladoceran Daphnia galeata mendota were prominent, in July D. galeata mendotae was the dominant cladoceran, and in August Diaphanosoma leuchtenbergianum was most abundant. The large cladoceran, Daphnia pulex, was present on most sample dates and the spectacular cladoceran, Leptodora kindtii was also present. The dominant cyclopoid copepods were Acanthocyclops vernalis, Mesocyclops edax and Diacyclops bicuspidatus thomasi; the dominant calanoid copepods were Diaptomus oregonensis and D. sicilis.
The benthic invertebrate community has not been studied in the littoral zone of Amisk Lake but crayfish (Orconectes virilis) are known to be present (Chipeniuk 1975). The benthic fauna of the sublittoral and profundal zones in both the north and south basins has been studied by University of Alberta researchers (Dinsmore and Prepas n.d.). From 15 May to 15 November 1988, 120 samples were collected with an Ekman dredge from the sublittoral zone of the north basin and 40 samples from the sublittoral zone of the south basin. For both basins, the dominant taxa were midge larvae (Chironomidae), aquatic earthworms (Oligochaeta), fingernail clams (Sphaeriidae) and scuds (Amphipoda). The average biomass (wet weight) for the north (3.8 g/m2) and south (3.0 g/m2) basins of Amisk Lake compare favourably with the average biomass (3.2 g/m2) measured in the sublittoral zone of Baptiste Lake but is substantially below the average biomass (6.2 g/m2) measured in the sublittoral zone of Narrow Lake.
For the same time period, 440 samples were collected with an Ekman dredge from the profundal zone in the north basin and 200 samples were collected from the profundal zone in the south basin. The dominant taxa were midge larvae and aquatic earthworms. The average biomass (wet weight) of 0.4 g/m2 in the north basin and 0.6 g/m2 in the south basin was much lower than the average biomass measured in the profundal zones of Baptiste (3.7 g/m2) and Narrow (2.3 g/m2) lakes.
The fish community includes yellow perch, northern pike, walleye, lake whitefish, cisco, white sucker, burbot, spottail shiner, brook stickleback, ninespine stickleback and Iowa darter (Norris 1987). The most popular sport fish is yellow perch.
There has been a commercial fishery on Amisk Lake since 1944 (Chipeniuk 1975). Initially, its focus was cisco, to provide animal food for local mink ranches. As the mink industry declined, the emphasis of the commercial catch shifted to lake whitefish, but there has been a continuing, though small, market for cisco as mink food (Stenton 1987). Small numbers of pike, perch and walleye are also caught by the commercial fishery. The historical average commercial harvest has dropped from 9,848 kg/year (1944 to 1961) to 4,913 kg/year (1981 to 1986) (Norris 1987).
In 1985 a creel census was conducted at Amisk Lake (Norris 1987). The number of fish caught per hour was high for yellow perch (1.94), low for northern pike (0.21) and poor for walleye (0.02). There were indications that all three species were being harvested at levels exceeding annual production. Both yellow perch and northern pike populations were skewed towards younger, smaller fish (3 to 5 and 2 to 5 year-olds, respectively). The estimated annual rates of production were: 3,120 kg/year for yellow perch, 1,300 kg/year for northern pike, 104 kg/year for walleye, 2,080 kg/year for lake whitefish and 2,600 kg/year for cisco.
Growth of young-of-the-year perch were studied from 1985 through 1987 by the University of Alberta (Abbey n.d.). Young perch grew from an average length of 5.9 mm when they hatched during the third week of May to 62 mm by early October. Growth rates of young perch in Amisk Lake were the highest of those in four deep lakes studied in the Boyle-Athabasca region.
There have been no detailed studies of the waterfowl at Amisk Lake. Ospreys are frequently seen fishing in the lake, and until 1988, had a nest on the island. In 1988, this nest was occupied by a pair of Bald Eagles. Mallards, Common Loons, and Red-necked Grebes nest on the lake and White Pelicans visit the lake to feed in late summer of most years (Prepas et al. n.d.).
Abbey, D. n.d. Univ. Alta. Unpubl. data, Edmonton.
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-----. n.d.[b]. Tech. Serv. Div., Surv. Br. Unpubl. data, Edmonton.
-----. n.d.[c]. Water Resour. Admin. Div., Water Resour. Br. Unpubl. data, Edmonton.
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Prepas, E.E. 1983[a]. The influence of phosphorus and zooplankton on chlorophyll levels in Alberta lakes. Alta. Envir., Res. Mgt. Div. Rep. 83/23, Edmonton.
-----. 1983[b]. Orthophosphate turnover time in shallow productive lakes. Can. J. Fish. Aquat. Sci. 40:1412-1418.
-----. and D.O. Trew. 1983. Evaluation of the phosphorus-chlorophyll relationship for lakes off the Precambrian Shield in western Canada. Can. J. Fish. Aquat. Sci. 40:27-35.
Prepas, E.E. and A.M. Trimbee. 1988. Evaluation of indicators of nitrogen limitation in deep prairie lakes with laboratory bioassays and limnocorrals. Hydrobiologia 159:269-276.
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-----. 1984[b]. Seasonal changes in total phosphorus and the role of internal loading in western Canadian lakes. Verh. Internat. Verein. Limnol. 223:303-308.
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Prepas, E.E., D.J. Webb, I. Wisheu, A. Trimbee, J.M. Hanson, J. Babin and T.P. Murphy. n.d. Unpubl. data, Univ. Alta., Edmonton and Natl. Water Res. Inst., Burlington, Ontario.
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