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Recovery Strategy for the Aurora Trout in Canada [Proposed]

1. Background

1 Species Information

COSEWIC Assessment

Summary Common Name: Aurora Trout
Scientific Name: Salvelinus fontinalis timagamiensis
COSEWIC Status: Endangered
COSEWIC Reason for designation: Formerly extirpated in the wild, re-introduced
populations of this species are dependant on continuing intervention such as liming of the lakes to buffer acidity Canadian Occurrence: Ontario
COSEWIC Status History: Designated Endangered in April 1987. Status re-examined and confirmed in May 2000. Last assessment based on an updated status report

General Biology:

Based on a 2003 survey, aurora trout in their native waters have a fork length distribution from 90 – 420 mm in Whirligig Lake and 60 – 490 mm in Whitepine Lake.  Adults weigh approximately 0.5 – 1.0 kg, although fish approaching 3.5 kg have been angled out of the stocked, non-native, put-grow-and-take waters.

Aurora trout are generalist feeders.  Although a large part of their diet is comprised of aquatic insects and zooplankton, they have also been found to consume crustaceans, mollusks, frogs and mice. 

Sexual maturity is attained between the ages of 2 – 4 years, and thereafter they are thought to spawn annually.  Spawning occurs in October and November and redds are cleared over groundwater upwellings.  Courtship and spawning behaviour have not been documented in either of the native lakes; however, it is expected to be similar to the spawning behaviour of brook trout.  While cases of hybridization with brook trout have beendocumented in non-native lakes (Sale 1967), the sympatric populations in Whitepine Lakeappeared to coexist with limited interbreeding.  This suggests that there may have been either spatial or temporal segregation in the spawning activities of the two species in Whitepine Lake.

Female aurora trout lay approximately 1300 to 1700 eggs.  Egg incubation periods documented within the hatchery environment suggest that incubation times are similar to hatchery brook trout (R. Ward, pers. comm.).

Based on field observations and laboratory aging, the maximum known lifespan in the wild is nine years.  

Distribution of the Species:

Aurora trout are endemic to only two lakes world wide.  Both Whirligig Lake (47º 22’ N, 80º 38’ W) and Whitepine Lake (47º 23’ N, 80º 38’ W) are located approximately 110 km north of Sudbury, Ontario within North Bay District (Figure 1).  The waterbodies are situated in the hilly Precambrian Shield landscape of Lady Evelyn-Smoothwater Provincial Park in the Montreal River watershed.  Other waterbodies have been thought to hold natural aurora trout populations (Henn and Rickenbach 1925, Sale 1967); however no authenticated records of additional native breeding populations have been found (Snucins and Gunn 2000). 

Whirligig Lake is 11 ha in size with a maximum depth of 9.1 m, a Secchi depth of 3.3 – 6.2 m and an end of summer thermocline of 3 – 8 m.  Whitepine Lake is 77 ha in size with a maximum depth of 21.3 m, a Secchi depth of 3.5 – 6.0 m and an end of summer thermocline of 4 – 9 m.   

Both native populations declined in the 1940s and 1950s, and were extirpated from the wild by the late-1960s as a result of acidification.  Re-introduction efforts during the early-1990s have re-established self-sustaining, naturally-reproducing populations in both of these waterbodies. 

In addition to the successful re-introductions of aurora trout in both native waters, there have been several efforts to establish a self-sustaining population in non-native waters in northeastern Ontario.  Previous efforts have included Paddle Lake, Reed Lake and Seahorse Lake (Kirkland Lake District) in the late-1950s and early-1960s, and Strong Lake in the 1980s; Lake # 8 Swartman (Cochrane District) in 1962; Young Lake and Claire Lake (Hearst District) in the mid- to late-1970s; Semple #54 Lake (Timmins District) in the 1990s and Lizard Lake (no date available); however none of these efforts were successful.  Stocking no longer occurs in any of these waters.  Southeast Campcot Lake (49º 03 N, 86º 37 W) and Northeast Campcot Lake (49º 03 N, 86º 37 W) near Terrace Bay were stocked in the late-1980s and showed evidence of natural reproduction by the early-1990s, unfortunately both populations appear to have been extirpated by 2001 (Snucins et al. 2002).   In 2004, aurora trout were again stocked in Southeast Campcot Lake. 

At the time of writing, there are non-reproducing aurora trout populations in ten waterbodies in northern Ontario; all of which are maintained through stocking of hatchery-reared fish from a captive breeding program.  The lakes are: Liberty Lake (47º 11 N, 80º 04 W), Carol Lake (47º 18 N, 81º 23 W), Pallet Lake (48º 16 N, 80º 39 W), Nayowin Lake (47º 47 N, 81º 23 W), Big Club Lake (48º 28 N, 80º 48 W), Wynn Lake (48º 16 N, 79º 53 W), Borealis Lake (49º 01 N, 86º 44 W), Tyrell #21 (47º 37’ N, 80º 57’ W), Timmins #57 (80º 67’ N, 48º 30’ W )and Alexander Lake (48º 17 N, 80º 35 W) (Figure 1).

Global distribution of aurora trout

 
 

Figure 1 Global distribution of aurora trout (Salvelinus fontinalistimagamiensis).   

 


This geographic enhancement of range is the result of (i) the establishment of a ‘wild’ brood stock lake (Alexander Lake) to facilitate and augment the captive breeding program within the hatchery system; (ii) efforts to establish a self-sustaining aurora trout population in a non-native waterbody with greater natural buffering capacity to act as a refuge in the event of re-extirpation of the native waterbodies or a catastrophic event within the hatchery that may compromise the existing aurora trout stock; and (iii) a two decade old effort to increase public awareness and generate public and stakeholder support for the aurora trout recovery program (and species at risk in general) by establishing a maximum of nine put-grow-and-take lakes.  These lakes provide limited trophy sport fisheries that are tightly regulated and operate on a seasonal, rotational basis (additional details on the rationale for the geographic range enhancement can be found in Section 12 – Activities Permitted by the Recovery Strategy). 

Population Abundance:

There are no historical population or biomass estimates available for Whirligig and Whitepine lakes.  Data collected during the early to mid-1950s prior to extirpation has been lost, precluding any comparison of the native lake populations between time periods. 

The treatment of Whirligig Lake and its headwaters with powdered calcite during October 1989 successfully raised the pH of the lake to 6.5.  Following treatment, hatchery-reared aurora trout were stocked in Whirligig Lake in the spring of 1990 and a naturally reproducing self-sustaining population was established (Snucins et al. 1995).  Whitepine Lake was stocked in 1991 and again in 1994 before a self-sustaining population developed.  Since this time, population abundance and biomass have increased in both lakes (Table 1).

Table 1.  Population and biomass estimates for the native aurora trout lakes (Whirligig Lake and Whitepine Lake).  Estimates are for fish >280 mm fork length in Whirligig Lake and >320 mm fork length in Whitepine Lake (except where indicated otherwise).  The figures in brackets represent 95% confidence intervals.

YearLake
 WhirligigWhitepine
 Population (N)Density (adults/ha)Biomass (kg/ha)Population (N)Density (adult/ha)Biomass (kg/ha)
19909501     
19912851  2471  
1993

4562

(337 – 639)

41

(31 – 58)

15.8

(11.2 – 23.1)

Not assessed Not assessed
1994   5001  
2003

418

(316 – 566)

38

(29 – 51)

17

(12.8 – 23)

2086

(1565 – 2845)

27

(20 – 37)

15.7

(11.8 – 21.4)

1 These values represent stocked hatchery-reared adults and juveniles of various ages.

2 The 1993 survey recorded fish >200 mm fork length

In addition to the two re-introduced native lake populations, as of fall 2003 a captive brood stock population of 2466 adult and sub-adult fish and 13,734 fall fingerlings were present at Hills Lake Fish Culture Station (R. Ward, pers. comm.).  Population estimates have not been conducted in Alexander Lake or in any of the put-grow-and-take lakes.  The stocking rates received by the angling waters are generally quite small and depend upon the number of lakes involved in any given year.  As an example, 38,800 fry (3 lakes), 6,000 fall fingerlings (2 lakes) and 619 adults (2 lakes) were stocked in 2001.  830 fry and 475 adults (1 lake each) were stocked in 2002, and 46,500 fry were stocked into 4 lakes in 2003.

Biologically Limiting Factors:

(i) Water Quality:

Aurora trout, similar to brook trout, require a pH of at least 5.0 for successful reproduction and maintenance of self-sustaining populations (Beggs and Gunn 1986).  Acidification from atmospheric pollutants in the form of acid rain, and possibly from historically deposited sulphur stored in adjacent wetlands, is believed to have been the proximate factor responsible for the extirpation of the wild aurora trout populations.  This continues to be the critical limiting factor to the success of the long-term recovery of aurora trout (Snucins and Gunn 2000).  The original extirpation of the native populations coincided with native lake pH levels declining to 5.0 and lower (Keller 1978).  Recovery initiatives to date have been successful because of water quality improvements resulting from reduced acid deposition and whole lake liming.  For the continued success of aurora trout, the pH of the lake water must be maintained at or above 5.0.

Dissolved oxygen concentrations in the lakes are relatively stable at 4 – 5 mg/L.  Sulphate concentrationshave declined in the lakes.  For example, in Whirligig Lake sulphate levels declined from 9.0 mg/L in 1987 to 6.5 mg/L in 2003.  This is in response to emission controls at the Sudbury smelters and at other more distant sources.  Alkalinity values for both native lakes are low, and thus the natural buffering capacity of the lakes is considered limited.

(ii) Spawning Habitat:

Groundwater upwellings appear to be a key physical feature for successful reproduction and the survival of fry to maturity.  Ideal spawning habitat has groundwater upwelling areas with a good flow of well-oxygenated water.  Both the groundwater and ambient lake water must have a pH greater than 5.0.  In Whirligig Lake, the only one of the two native lakes to have spawning sites documented, all spawning occurs within the lake environment on groundwater seepages in shallow water (4 m or less) over sand, gravel and rock substrate.  The location of spawning sites in Whitepine Lake is generally known, but has not been formally documented or characterized.  Snucins and Gunn (2000) speculated that the inability of the introduced aurora trout populations in the non-native lakes to establish self-sustaining populations was due to the lack of suitable spawning sites with groundwater discharge.

Description of the Habitat Requirements of the Species:

Auroratrout display water quality and thermal requirements similar to brook trout.  In general, a good brook trout lake is a good aurora trout lake.  Aurora trout prefer cool well-oxygenated lake environments where water temperatures are generally below 20oCand dissolved oxygen levels are approximately 5 – 6 mg/L or above.  During the summer months aurora trout seek cooler temperatures as the surface waters warm and a thermocline appears.  Aurora trout will congregate at or below the thermocline or utilize cooler localized water temperatures created by groundwater seeps.  As previously mentioned, a pH of 5.0 or greater is necessary for successful reproduction.  Spawning habitat requirements are outlined in the previous section.

1. Threats

Acidification:

Acidification from atmospheric pollutants in the form of acid rain is believed to have been the proximate factor responsible for the extirpation of the wild aurora trout populations and continues to be the primary biological threat to the re-introduced populations (Snucins and Gunn 2000).  Aurora trout, like brook trout, require a pH of at least 5.0 for successful reproduction and the maintenance of self-sustaining populations (Beggs and Gunn 1986).  Extirpation of the native populations occurred at about the time lake pH levels reached approximately 5.0 (Keller 1978).  pH levels in Whirligig and Whitepine lakes remained incompatible with the survival of aurora trout from the late-1960s through to the late-1980s.  Studies done in the native lakes during the 1980’s showed that the groundwater sites typically used for spawning had suitable water quality for survival of the embryonic stages, but that the ambient lake water was limiting survival after emergence from the substrate (Snucins et al. 1988).

Whole lake liming raised pH levels to about 6.5 in Whirligig Lake and natural recovery improved the water quality in Whitepine Lake (Snucins and Gunn 2000).  Aurora trout brood stock was re-introduced in Whirligig Lake (1990) and Whitepine Lake (1991 and 1994) and self-sustaining populations have resulted.  While pH has shown indications of decline throughout the late-1990s and early-2000s, a field assessment in 2003 demonstrated that pH remained greater than 5.1 in both lakes.  A trend analysis revealed that sulphate concentrations have declined over time.  It is hoped the concentrations may now be low enough that further declines in pH will not occur and that current conditions will be maintained or improved (E. Snucins, pers. comm.).  The current pH of Whirligig Lake is about 5.1 – 5.3 and is similar to the background pH of 5.3 estimated from diatom remains in sediment cores (Dixit et al. 1996).  The current pH of Whitepine Lake is 5.1, which is still below the estimated background level of 5.4 – 5.7.

Loss of Adaptive Fitness Due to Inbreeding Depression:

All descendents of today's aurora trout can be traced back to a single egg collection event in 1958 that involved only 3 females and 6 males (assuming all males contributed genetic material to the breeding).  The low founding numbers, 40 years of captive breeding history and supplemental stocking back into the lakes that were the source of breeding individuals has led to speculation that the potential for inbreeding depression exists.  The consequence would be a reduction in reproductive fitness (i.e. loss of adaptive ability to respond to ecological stresses) compared to of the original population. 

While it is possible that the original population may have had a naturally low genetic diversity, which would be a reflection of their adaptation to a narrow environment, the occurrence of inbreeding appears to be supported by genetic and circumstantial hatchery evidence.  Previous allozyme monitoring of the hatchery population has shown that the aurora trout strain is the most genetically uniform of the 99 brook trout stocks examined in Ontario (only minor variation in two genetic loci observed).  Mitochondrial DNA analysis identified that aurora trout carried only one genome type, the locally common brook trout haplotype. 

Further evidence indicative of inbreeding depression comes from direct observations within the captive breeding program and from the brood stock in Alexander Lake.  Low survivorship of early life stages in the hatchery environment has been observed (R. Ward and C. Wilson, pers. comm.).  There is a lack of reproduction in Alexander Lake despite high stocking numbers and good survival to adulthood (C. Wilson, pers. comm.) and there is a highly skewed sex ratio of mature adults in Alexander Lake (R. Ward, pers. comm.)  Although, it should be noted that the lack of reproduction within Alexander Lake and the nine put-grow-and-take lakes may be more a result of a lack of suitable spawning habitat (Snucins and Gunn 2000) than to inbreeding depression.   

As well, analyses of aurora trout within a controlled hatchery environment have shown survivorship of aurora trout to be far less than that of Nipigon strain brook trout or experimental crosses between brook trout and aurora trout.  It is suspected that this may be due in part to a weakened immune response capability which leads to greater susceptibility to stress and disease.  In a follow-up experiment pure strain aurora trout were treated with an anti-fungal agent and survivorship increased dramatically (C. Wilson, pers. comm.). While further studies need to be conducted to clarify the threat to long-term survival, preliminary observations of low genetic diversity and low reproductive fitness indicate inbreeding depression.

Climate Change:

Although no documentation exists specific to aurora trout lakes, global climate change may be a concern.  In other areas of the province, warmer water associated with climate change is having a negative impact on fish populations, including observations of brook trout mortality as far north as the Sutton River, one of the larger river systems of the Hudson Bay Lowlands (E. Snucins, pers. comm.).    In addition, climate change could cause a re-acidification of the native lakes.  It is not known if a significant amount of sulphur is stored in the watershed of the aurora trout lakes.  If a significant amount does exist, then a period of prolonged drought could create conditions that may cause a re-acidification event.

Others:

With the two native lakes occurring within a protected landscape, Lady Evelyn-Smoothwater Provincial Park, the following issues may not apply specifically to the re-established native populations.  However, these issues should be considered for Alexander Lake, any future non-native lake being considered for the establishment of a self-sustaining population, and for all nine put-grow-and-take angling lakes.

Land Use Practices:

Based upon current knowledge, aurora trout are limited to lake environments and require certain habitat parameters, the most important of these being a suitable pH and thermal regime at sites used for spawning.  Habitat suitability is susceptible to land use activities which may directly or indirectly impair functionality.  Most notably, anthropogenic activities such as resource extraction (e.g. forestry practices, mining, etc.) or road building, have the potential to disrupt the quality and quantity of groundwater which enters the lake, thus impairing the groundwater discharge that provides essential thermal and spawning habitat. 

Forestry practices may also have the potential to affect the pH of a lake (Watmough et al. 2003).  The harvesting of trees removes a major source of base cation deposition to the soil.  Initially there may be an increase in base cations available to the soil as logging debris decays, but over the long-term it is expected that base cation deposition rates would decrease.  Base cations are transferred from terrestrial ecosystems to adjacent aquatic ecosystems through the leaching of soil minerals in runoff.  Reduced concentrations of base cations will reduce the buffering capacity of the lake and increase acid sensitivity.

Introduction of Invasive Species:

Brook trout have been demonstrated to be vulnerable to competition from other species, notably yellow perch, Perca flavescens (Fraser 1978).  Given the strong biological similarities between brook trout and aurora trout, it is anticipated that aurora trout may also be susceptible to competition from spiny-rayed fishes.  To prevent the accidental introduction of other competitors, which would likely displace aurora trout, all lakes with natural reproduction (i.e. Whitepine, Whirligig, Northeast Campcot and Southeast Campcot lakes) have been designated as provincial fish sanctuaries.  This status prohibits any sport angling, hence minimizing the potential for accidental or intentional introductions.  This same sanctuary status has also been granted to Alexander Lake.  In the remaining lakes, where limited recreational trophy angling opportunities are permitted, the use of live baitfish is prohibited to reduce the risk of accidental introductions of competitors.

The accidental introduction of other invasive species, such as aquatic plants or invertebrates, could also have an impact on aurora trout.  For example, the spiny waterflea (Bythotrephes sp.) has invaded lakes across southern Ontario and is now being found in lakes in northern Ontario as well.  The invasion of spiny waterfleas generally results in a significant shift in the zooplankton community of a lake, with Bythotrephes becoming dominant in the species assemblage.  Although the effect of such a shift on the recovery, survival and health of aurora trout is unknown, the types of prey available to the fish would likely change. 

The mechanism of invasion for such species is generally on the hulls of boat, the pontoons of aircraft or on other equipment that may be used in multiple lakes without proper washing.  It is difficult to address this problem on the angling lakes that are open to the public once every three years.  A program to increase angler education regarding invasive species has been initiated in northern Ontario by the OMNR Invasive Species program and the Ontario Federation of Anglers and Hunters (OFAH).  Accidental introductions to the native lakes are easier to control as these lakes are remote and difficult for the public to access.  The landing of aircrafts in Provincial Parks requires a permit and thus is controlled by Ontario Parks.  Ontario Parks has indicated that the Lady Evelyn-Smoothwater Provincial Park Management Plan (currently in preparation) will include a protocol for reducing the risk of invasive species that will apply to researchers and recovery workers accessing lakes in the park (E. Morris, pers. comm.).  This protocol should be developed in consultation with researchers that are currently working within the park.

Illegal Harvesting:

To date, poaching has not been considered to be a major problem.  Only one case of poaching has been well documented.  In 1994, a small group of poachers were apprehended and charged on Southeast Campcot Lake.  Nipigon District Enforcement staff have frequently patrolled both Northeast and Southeast Campcot lakes before and after this incident, up until 2001 when it was realized that the introduction had failed.  It did not appear that any additional incidents occurred.  The reason for the extirpation of the Campcot populations is unknown.  There are no documented incidents of poaching on any of the other aurora trout lakes.