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Recovery Strategy for the Aurora Trout in Canada [Proposed]

2. Knowledge Gaps:

The following briefly summarizes key knowledge gaps that should be addressed as information becomes available to assist with recovery efforts.  Actions to address these gaps, where feasible, appear in Table 2 (see Section 5 (c)).

  1. Historical population abundance and biomass measures are not available.  Efforts to locate historical population data, including contacting the primary individual responsible for the early population assessments have been unsuccessful (E. Snucins, pers. comm).  Thus, historical reference points were not available for setting recovery targets.  Population assessments were conducted in Whitepine and Whirligig lakes in the fall of 2003 to determine the current population status of aurora trout within their native waters.  These results were of assistance to the recovery team in the completion of this strategy.
  2. The status report for aurora trout is currently in draft form only.  The species assessment by COSEWIC and the subsequent development of a recovery strategy have utilized the draft status report.  This report needs to be finalized.   Although this is not a knowledge gap per se, this is an information gap that needs to be addressed.
  3. As indicated in Section 2 b) of this document, preliminary evidence suggests inbreeding may be an issue with aurora trout (C. Wilson, pers. comm.).  Further examination of this is required.  To assist in this, 100 genetic samples were taken from each of the re-established native lake populations in the fall of 2003.  The samples were submitted to the OMNR genetics laboratory in Peterborough for analysis to determine if any divergence has occurred among the wild fish, the current hatchery stock and the population in Alexander Lake (E. Snucins, pers. comm.).
  4. Further genetic assessment is required to establish the true taxonomy of aurora trout.  To date, genetic examinations have not provided support for a subspecies designation.  As noted previously, the investigation of allozyme data by OMNR staff in the 1990s demonstrated aurora trout had very low levels of genetic variation but no unique alleles when compared against brook trout (C. Wilson, pers. comm.).  Grewe et al. (1990) and Danzmann (unpubl. data, C. Wilson, pers. comm.) both found that mitochondrial DNA (mtDNA) failed to show fixed diagnostic differences in molecular markers that would suggest genetic separation between aurora trout and brook trout.  However, broader mtDNA work by Reed et al. (1998) has shown that subspecies and even sister species in Canada generally cannot be discriminated based on mtDNA, and mitochondrial divergence between sister species in deglaciated areas is generally quite low (Bernatchez and Wilson 1998).  Thus, genetic evaluations completed to date on aurora trout may not have been able to detect differences.
  5. Advancements in the use of new genetic assessment markers like nuclear ITS (internal transcribed spacer) regions or gene introns may clarify the taxonomy of aurora trout.  The outcome of such research would provide key information for a future status assessment by COSEWIC.  As well, the information could assist in refining management options, specifically in the areas of experimental crossings, match plantings or gene infusion opportunities that may increase the genetic fitness of aurora trout.  If aurora trout are found to be genetically distinct, crossings with brook trout and the infusion of brook trout genes will not be considered as a management option.
  6. A formal captive breeding policy does not exist and is required, especially in light of the aforementioned potential for loss of adaptive reproductive fitness.  It has been left up to the knowledge of staff at the Hills Lake Fish Culture Station (HLFCS) (with assistance as needed from other ministry staff) to look after breeding and culture of the aurora trout. Captive breeding has been underway at the HLFCS since 1958.  Prior to the early-1980s captive domestic (hatchery raised) aurora trout were spawned by putting eggs from one or two females with the milt of at least two males and the eggs were pooled in order to maximize successful fertilization without regard for family distinction.  The resulting progeny were used in efforts to establish a self-sustaining population in a non-native waterbody, in support of the angling lakes and every second year 10,000 fry were placed into Alexander Lake.  After this time, following discussions with OMNR’s fish geneticist, a strategy was initiated by hatchery staff to try and increase family lines. 
  7. Currently the breeding strategy employs a family approach (one male to one female) from the domestic brood stock with each fish only being bred once.  Egg collection targets vary on an annual basis depending upon recovery targets and the number of angling lakes due for stocking.  Generally 20 families (ranging from 16 – 25 families) are collected from Alexander Lake bi-annually (this produces approximately 25,000 – 30,000 eggs).   The families are incubated separately until the eyed-egg stage.  At this time, even numbers are counted from each family to form the new hatchery brood stock with the remainder being returned to Alexander Lake.  In addition to the egg collection at Alexander Lake, 100,000 - 150,000 eggs are collected each year from the captive hatchery brood stock population for the stocking of fry into the angling lakes.   Presently, fish are stocked back into Alexander Lake every year to maximize the number of year classes (and hopefully the number of family lines) in the brood stock lake.    
  8. Spawning habitat assessments are required.  Spawning site locations and general habitat descriptions have been documented for Whirligig Lake, but only general locations are known for Whitepine Lake.  It is presumed that all known sites in both lakes are at groundwater upwelling locations, however flow measurements are required for confirmation.  Detailed descriptions and mapping of spawning sites are also required for Whitepine Lake.  Although it has been speculated that the reason aurora trout in Alexander Lake are not reproducing is because of a lack of suitable spawning habitat, this requires confirmation. 
  9. Great strides in recent emission controls have significantly lowered atmospheric pollutants (especially sulphur) from smelters located in Sudbury and other distant sources.  This has assisted in the recovery of the native lakes.  It would be useful to determine whether or not current acid deposition levels exceed the critical load for the native aurora trout lakes (to ensure that the pH remains above 5.0).

3. Recovery Feasibility:

The recovery of aurora trout is technically and biologically feasible.  Self-sustaining populations have been restored in both native waters with successful reproduction occurring in Whirligig Lake since 1990 and in Whitepine Lake since 1994.  Both populations are at biomass levels well within the range documented for brook trout in similar low productivity oligotrophic lakes.  Of particular importance, a recent evaluation revealed that the aurora trout populations are in good condition with no evidence of missing year classes in either lake.  Missing year classes would be considered an early indicator that the populations are under acid stress (E. Snucins, pers. comm.).  The biomass and abundance of aurora trout in Whirligig Lake did not change significantly between 1993 and 2003.

Suitable habitat for the recovery of aurora trout is available in both of the native lakes.  Water quality monitoring has been undertaken since 1987, and despite the presence of short-term transient pH depressions in 2001 and 2002, water quality remains good with a pH of 5.1 - 5.3 in Whirligig Lake and 5.1 in Whitepine Lake.  The natural background pH, as estimated from diatom remains found in sediment cores, is 5.3 for Whirligig Lake and 5.4 – 5.7 for Whitepine Lake (Dixit et al. 1996).  No further powdered calcite treatments (to increase pH) have been required in either lake since 1995. 

Trend analysis of water chemistry data has demonstrated that sulphate concentrations continue to decline and current readings may be low enough that further pH depressions will not occur.  The trend of declining sulphate concentrations is consistent with the general patterns observed in other Northeastern Ontario lakes (Keller et al. 2001).  Recent emission control measures introduced in early 2004 by the Ministry of the Environment (MOE) at Sudbury area smelters, in conjunction with similar emission reduction initiatives undertaken in other jurisdictions, has enhanced the potential for these waterbodies to continue to maintain suitable pH levels for successful self-sustaining populations.  There have been a number of other cases where biological recovery has followed water quality recovery, both locally (i.e. within the deposition zone downwind of Sudbury) and in other jurisdictions.  While all of this suggests a brighter future for aurora trout, only time and the continuance of a long-term monitoring program will indicate whether recovery efforts to re-establish self-sustaining aurora trout populations within the native waters have succeeded.  In the end, the biological recovery is dependent on re-acidification being prevented. 

Although suitable habitat is available in both native lakes and the re-introduced populations have been maintained by natural reproduction for over 10 years, it appears that spawning habitat is very limited or absent in Alexander Lake and the nine angling lakes.  For this reason, the ATRT is continuing to investigate the possibility of establishing one or two naturally reproducing, non-native satellite populations.  Northeast Campcott and Southeast Campcott Lakes were stocked with aurora trout in the late-1980s, were confirmed to have naturally reproducing populations in the early-1990s, but appear to have been extirpated by 2001.  Since the cause of the extirpation remains unknown, it has been decided that Southeast Campcott Lake will be stocked again.  The condition of the lake environment and the status of the population will be monitored carefully.  The establishment of one other naturally reproducing aurora trout population is still desirable, possibly in a location more proximate to the watershed of the native lakes.  Little Whitepine Lake, located just upstream of Whirligig Lake, is a possible candidate.  Prior to stocking this lake, such a proposal would require the authorization of the Park Superintendent of Lady Evelyn-Smoothwater Provincial Park, the completion of a Class Environmental Assessment for Provincial Parks and Conservation Reserves and the completion of the risk assessment screening outlined in the National Code on Introductions and Transfer of Aquatic Organisms.

It appears that threats to the survival of the native populations can largely be minimized, mitigated or eliminated.  The native lakes appear to be recovering from acidification and aurora trout are successfully reproducing in both lakes.  It will be critical to continue monitoring these lakes to ensure that additional intervention (i.e. whole lake liming) is not necessary.  Since both lakes are remote and located in a Provincial Park, the risk of accidentally introducing non-native species can be minimized, poaching is unlikely and the effects of anthropogenic land use disturbances are minimal.  It is hoped that the issues surrounding the genetic diversity and adaptive fitness of aurora trout can be optimized through the captive breeding program.  Depending on the results of the genetic taxonomic assessment, the infusion of brook trout genes to increase diversity may be an option.  As for all coldwater fish species, the possible effects of future climate change remain uncertain.

The recovery techniques used to date appear to be highly successful.  The techniques (including captive breeding, stocking and whole lake liming) are commonly used recovery techniques.  Past industrial emissions reduction programs have been successful in reducing acid deposition in central and northeastern Ontario.  The latest initiative undertaken by MOE and several industries in Sudbury will only help the situation.