Population trends and status of the fishery

Lake trout are native to the area and Ontario supports a significant proportion (25%) of naturally reproducing native populations worldwide. Lake trout have experienced considerable losses across their native range in eastern North America primarily resulting from a loss of habitat and through competition with other species. Lake trout populations have been dramatically reduced in areas where shoreline developments are abundant. FMZ 18 supports a limited, but quality lake trout fishery.

Of the 871 named lakes in the zone, 58 are managed as lake trout lakes. In most cases, when lake trout are present, the lake is primarily managed for this species. However, remnant (very low density) lake trout populations still remain in a few coldwater lakes which are now managed for other fish species. A review of FMZ 18’s lake trout populations suggest that 24% of the lakes contain small-bodied lake trout that feed mainly on invertebrates and small fish; 68% of the lakes have cisco (lake herring), lake whitefish and/or rainbow smelt as prey, resulting in larger bodied lake trout; and 8% are currently classified as unknown, requiring assessment to determine their type.

Small-bodied lake trout

Small-bodied lake trout populations across FMZ 18 were surveyed between 1997 and 2010, using the Spring Littoral Index Netting (SLIN) and Summer Profundal Index Netting (SPIN) survey methodologies. There were a total of 6 SLIN and 10 SPIN surveys conducted on four and nine lakes, respectively in FMZ 18. In addition, BsM, monitors the fish community including lake trout and was conducted on three small-bodied lake trout lakes in FMZ 18 from 2008 to 2010.

Lake trout abundance, which is impacted by harvest and quality of habitat, is estimated by the average number of lake trout per net (CUE), which varies across FMZ 18. The small-bodied lake trout mean catch rate from a limited number of SLIN surveys (6 surveys, 4 lakes) is 3.8 lake trout/net in FMZ 18, compared to about 3.2 lake trout/net for FMZ 5 (zone in Northwestern Ontario with the highest number of lake trout Fisheries). The small-bodied lake trout mean catch rate from SPIN is 0.8 lake trout/net in FMZ 18.

The mean catch rate from the BsM surveys is 1.8 lake trout/net in FMZ 18. The relative abundance of lake trout in southern Ontario may, however, be vulnerable to a higher number of stressors which they are generally exposed to, relative to northern Ontario. The prevalence of shoreline alteration, industrial and agricultural contaminations, and changes to fish communities, including invasive species introductions, tends to be higher in the south.

A greater number of age classes and high maximum age are indicative of successful recruitment and adult survival. The assessment data show that few lake trout are reaching the common southern Ontario maximum age of approximately 20 years (McCauley, 2011) suggesting low survival. Only <1% (BsM); 0% (SLIN); and <1% (SPIN ) of the small-bodied lake trout were 15 years or older, with the following total number of year classes 15 (BsM); 11 (SLIN); and 12 (SPIN ). The median age for lake trout caught was 7; 6; and 5 years for BsM, SLIN and SPIN surveys, respectively. This recently collected data suggests that lake trout populations are showing signs of high mortality with mean ages ranging from 6 to 8 years; 6 to 7 years; and 5 to 7 years for BsM, SLIN and SPIN surveys, respectively.

Large-bodied lake trout

Large-bodied lake trout populations across FMZ 18 were surveyed between 1994 and 2012, using the SLIN and SPIN survey methodologies. There were a total of 30 SLIN and 8 SPIN surveys conducted on 19 and 7 lakes, respectively in FMZ 18. In addition, BsM, monitors the fish community including lake trout and was conducted on 13 large-bodied lake trout lakes in FMZ 18 from 2008 to 2010.

The large-bodied lake trout mean catch rate from the SLIN surveys is 1.4 lake trout/net in FMZ 18, compared to about 1.5 lake trout/net for FMZ 5 (zone in Northwestern Ontario with the highest number of lake trout Fisheries). The large- bodied lake trout mean catch rate from the SPIN surveys is 0.6 lake trout/net in FMZ 18.

The mean catch rate from the BsM surveys is 0.5 lake trout/net in FMZ 18. 12% (BsM); <1% (SLIN); and 0% (SPIN) of the large-bodied lake trout were 15 years or older, with the following total number of year classes 24 (BsM); 12 (SLIN); and 8 (SPIN ). The median age for lake trout caught was 8; 7; and 4 years for BsM, SLIN and SPIN surveys, respectively. This recently collected data suggests that lake trout populations may be showing signs of high mortality with mean ages ranging from 6 to 17 years; 4 to 8 years; and 4 to 5 years for BsM, SLIN and SPIN surveys, respectively.

Lake trout may be affected by impacts other than angling such as climate change, species introductions, or habitat impacts, more so than most other sport fish species. The introduction of zebra mussels into many of the lake trout lakes in FMZ 18 in recent years may have further increased the water clarity. Although such an invasion was initially thought to have minimal impact on lake trout fisheries, recent evidence suggests that it may have caused major shifts in the species’ forage base, in some lakes (Evans, 2012). This factor may limit the productive capacity of lake trout and must be considered when assessing the effectiveness of management actions.

In summary, lake trout populations in FMZ 18 are currently considered to be at relatively moderate abundance but with certain populations showing signs of high mortality. Most populations have high proportions of fish at or near maturity, but lack large, older fish. The management focus for this species is to try and maintain its distribution and abundance at, or in certain cases, increase population abundance beyond current levels.

Lake trout management in FMZ 18

The decline in lake trout abundance and distribution of certain fisheries in FMZ 18 has been recognized as a concern and a priority in the fisheries management plan. MNRF and the Advisory Council identified a number of challenges to managing lake trout populations in the FMZ 18.

Management challenges:

  • habitat degradation or destruction caused by shoreline development; increased nutrient levels from faulty septic systems or shoreline erosion; and climate change causing an increase in thermal regime
  • low abundance of mature fish
  • sustained high level of fishing effort for lake trout
  • harvest demand is exceeding the current supply of lake trout in certain fisheries
  • fish introductions into simple fish communities creating competition for limited resources

The MNRF with the advice of the Advisory Council developed objectives and strategies to address the challenges and help reach the following lake trout management goal.

Goal:

To maintain current lake trout populations and where possible, increase these populations.

Objective 1:

Maintain native, naturally reproducing lake trout lakes.

As previously noted, often the main contributing factor to the decline of a lake trout fishery is a reduction of suitable habitat. Managing various detrimental impacts such as limiting the amount of shoreline development to reduce the input of nutrients may prove to be the most effective technique for managing critical deep water habitat for lake trout.

Unique genetic stocks of lake trout have been identified in FMZ 18. These strains exhibit the small-bodied, planktivorous traits typical of southern Ontario inland lakes, and genetic analysis suggests that, despite previous years of stocking Great Lakes strains, fish from these inland lakes show little evidence of interbreeding with fish from the provincial hatchery program. The local strain of lake trout has genetic markers that indicate they have been isolated for a longer-than-normal period of time. Essentially, they represent the most genetically unique populations of lake trout yet to be identified in Ontario; remnants of the lake trout population which dispersed following the retreat of the glaciers. To date, samples have been collected from a number of local lakes and results of the genetic analysis will help identify, map and conserve the special, locally adapted strains of lake trout. This objective of the lake trout management strategy in FMZ 18 is aimed at ensuring these unique, natural lake trout populations are sustained.

Lake trout stocking (other than PGT) should only occur to rehabilitate significantly depleted populations, while also addressing the factors which have caused the significant reduction in lake trout abundance. Unfortunately, in many cases, the main contributing factor to the decline of a lake trout fishery is the lack of suitable deep water habitat, stemming from various negative impacts such as shoreline development erosion, sedimentation, faulty septic systems, climate change (warming thermal regime), invasive species introductions, etc. Stocking practices for rehabilitation purposes should also consider the importance of the genetically unique strains of the existing populations.

Strategies to address the objective include:

  • reduce angler harvest on naturally-reproducing lakes by encouraging harvest from PGT lake trout fisheries and/or of other species
  • minimize the introduction of new species into lake trout lakes by working with partners and stakeholders to convey messaging on prevention
  • identify vulnerable lake trout populations, based on lake capacity assessments, and share this information with municipalities to enable effective land use planning
  • engage stakeholders to increase awareness, promote and undertake rehabilitation to enable natural shorelines
  • explore opportunities to collect tissue samples to enable the identification of lake trout genetic stocks to better enable identification of effective rehabilitation tactics that may be required to address climate change or other pressures
  • for seriously degraded lake trout populations where limited recruitment is occurring, consider using rehabilitation stocking as a means to allow population recovery, as appropriate (as per Fish Stocking Approach Section)

Objective 2:

Increase lake trout abundance and the number of sustainable populations.

MNRF’s Provincial Fish Strategy and the FMZ 18 Advisory Council places priority on naturally reproducing, self-sustaining populations. A number of strategies are outlined in this document which may increase lake trout abundance and improve the quality of angling opportunities. It was also recognized that PGT fisheries could provide additional angling and harvest opportunities, as well as direct lake trout angling pressure away from naturally reproducing fisheries.

Strategies to address the objective include:

  • assess the status of lake trout populations and the fisheries they support
  • for unknown lakes/populations, determine the lake trout size phenotype (large or small body classification) to inform future population management
  • develop public/partner opportunities to measure fishing pressure and harvest rates via public reporting (e.g. volunteer angler diary program)
  • stock PGT lakes to divert fishing pressure away from native lake trout fisheries
  • identify sustainable lake trout management science priorities and share/promote these priorities with MNRF science and academia

Objective 3:

Increase natural lake trout recruitment.

Lake trout concentrate at specific sites to spawn each fall on rocky shoals in lakes. It is important to identify, enhance and protect these sites to ensure sustainable lake trout populations. Lake trout spawning habitat can be impacted by fluctuating water levels and flows. It is important to maintain consistent water levels and flows during the spawning/incubating/hatching period of lake trout. If the water levels are lowered during this time period, eggs may be killed if they are exposed to ice/air. There are numerous dams and hydropower facilities in FMZ 18 that control flows and levels that could impact lake trout spawning success.

As previously noted, often the main contributing factor to the decline of a lake trout fishery is a reduction of suitable habitat. Managing various detrimental impacts such as limiting the amount of shoreline development (via municipal land use planning process and applying the lake trout capacity model) to reduce the input of nutrients may prove to be the most effective technique for managing critical deep water habitat for lake trout.

Strategies to address the objective include:

  • identify lake trout populations that are vulnerable to development pressure (e.g. lake trout capacity model) and communicate this information to planning authorities and other regulatory authorities (including MNRF through the water management planning process) to enable protection of vulnerable populations
  • work with stakeholders to identify spawning areas and rehabilitative needs, and monitor spawning shoals of lake trout fisheries with recruitment concerns
  • share fishery management objectives, spawning locations and other habitat information (e.g. LIO) with partner agencies to enable the protection of these important areas through land use planning and application of their regulatory mandates (e.g. DFO and Fisheries Act)
  • expand and share knowledge of lake trout recruitment requirements through scientific research

Objective 4:

Maintain lake trout angling opportunities.

MNRF and the Advisory Council agreed that certain lake trout populations in FMZ 18 have declined in recent years and some have been extirpated all together or converted to PGT fisheries. As a counter-measure, PGT lakes are stocked for the sole purpose of providing angling and harvesting opportunities, and their establishment within the zone allows for more liberal regulations on some waterbodies and may absorb angling pressure from more sensitive, native lake trout lakes.

Strategies to address the objective include:

  • maintain existing seasons
  • maintain existing PGT lake trout lakes, where effective, to create alternate angling opportunities, as well as winter fishing opportunities

The goal, objectives and strategies have been summarized in Table 2.

Table 2: lake trout management summary

Adapted from tabular format

Lake trout management goal:

To maintain current lake trout populations and where possible, increase these populations.

Objective 1:

Maintain native, naturally reproducing lake trout populations.

Strategies
  • Reduce angler harvest on naturally-reproducing lakes by encouraging harvest from PGT lake trout fisheries and/or of other species.
  • Minimize the introduction of new species into lake trout lakes by working with partners and stakeholders to convey messaging on prevention.
  • Identify vulnerable lake trout populations, based on lake capacity assessments, and share this information with municipalities to enable effective land use planning. 
  • Engage stakeholders to increase awareness, promote and undertake rehabilitation to enable natural shorelines.
  • Explore opportunities to collect tissue samples to enable the identification of lake trout genetic stocks to better enable identification of effective rehabilitation tactics that may be required to address climate change or other pressures.
  • For seriously degraded lake trout populations where limited recruitment is occurring, consider using rehabilitation stocking as means to allow population recovery, as appropriate (as per Fish Stocking Approach Section).
Progress reviewed by

Every BsM cycle

IndicatorBenchmarkTarget

# of native lake trout lakes

N/A

Current # of native lake trout lakes

# of native lake trout genetic strainsN/ACurrent # of lake trout genetic strains
Objective 2:

Increase lake trout abundance and the number of sustainable populations.

Strategies
  • Assess the status of lake trout populations and the fisheries they support.
  • For unknown lakes/populations, determine the lake trout size phenotype (large or small body classification) to inform future population management.
  • Develop public/partner opportunities to measure fishing pressure and harvest rates via public reporting (e.g. volunteer angler diary program).
  • Stock PGT lakes to divert fishing pressure away from native lake trout fisheries.
  • Identify sustainable lake trout management science priorities and share/promote these priorities with MNRF science and academia. 
Progress reviewed by

BsM Cycle 3

IndicatorBenchmarkTarget
Median area weighted CUEW (all lakes combined from BsM)Current kg/net> Current kg/net
BsM Proportion of lakes where biomass ratio (B/Bmax) is > 0.5Current % of lakes> Current % of lakes
BsM Proportion of lakes where mortality rate ratio (Z/M) is < 2Current % of lakes> Current % of lakes
Objective 3:

Increase natural lake trout recruitment.

Strategies
  • Identify lake trout populations that are vulnerable to development pressure (e.g. lake trout capacity model) and communicate this information to planning authorities and other regulatory authorities (including MNRF through the water management planning process) to enable protection of vulnerable populations.
  • Work with stakeholders to identify spawning areas and rehabilitative needs, and monitor spawning shoals of lake trout fisheries with recruitment concerns.
  • Share fishery management objectives, spawning locations and other habitat information (e.g. LIO) with partner agencies to enable the protection of these important areas through land use planning and application of their regulatory mandates (e.g. DFO and Fisheries Act).
  • Expand and share knowledge of lake trout recruitment requirements through scientific research.
Progress reviewed by

BsM Cycle 3

IndicatorBenchmarkTarget
BsM mean # of Young of the Year (YOY) fish < 100 mmCurrent BsM mean # of Young of the Year (YOY) fish < 100 mm> Current BsM mean # of Young of the Year (YOY) fish < 100 mm
BsM mean # of juvenile fish (< 300 mm (small-bodied) and < 450 mm (large-bodied)Current BsM mean # of juvenile fish (< 300 mm (small-bodied) and < 450 mm (large-bodied)> Current BsM Mean # of juvenile fish (< 300 mm (small-bodied) and < 450 mm (large-bodied)
BsM mean # of year classesCurrent BsM Mean # of year classes> Current BsM Mean # of year classes

Objective 4:

Maintain lake trout angling opportunities.

Strategies
  • Maintain existing seasons.
  • Maintain existing PGT lake trout lakes where effective, to provide alternate angling opportunities, as well as winter fishing opportunities.
Progress reviewed by

BsM Cycle 4

IndicatorBenchmarkTarget
# of days of the lake trout seasonN/ACurrent # of days of the lake trout season
# of PGT lake trout lakesN/ACurrent # of PGT lake trout lakes

Lake trout monitoring and assessment

The provincial BsM program is the primary survey method used to collect fisheries data in Ontario, including lake trout. The BsM program provides information about fish abundance, population structure, growth, maturity and fishing effort. The BsM program will be able to report on the trends and status of fisheries at the FMZ scale. The fish community will also be assessed to determine changes in species composition over time.

Strategies:

  • adopt the BsM program as the primary index netting (and effort census) survey to assess lake trout population (and its pelagic forage base) status across FMZ 18
  • monitor lake trout populations using standard netting protocols (e.g. BsM, SPIN) to address specific management concerns that arise on lakes not sampled as part of the BsM program
  • work with partners/stakeholders to explore a program to monitor lake trout spawning activity and spawning rehabilitative needs (“Lake Trout Watch”)
  • develop public/partner opportunities to measure fishing pressure and harvest rates via public reporting (e.g. volunteer angler diary program)

Current lake trout regulations:

Regulations for lake trout in FMZ 18 are consistent with the regulatory guidelines for native and stocked PGT fisheries, in terms of seasons and catch limits. A year round open season for PGT fisheries; an open season from the 4th Saturday in May to September 8th for native fisheries; and no size restrictions are currently in place for either type of fishery. A catch and possession limit of two (2) lake trout (which are included in the aggregate limit of five (5) trout (including splake) applies to sport license holders (one (1) for conservation license holders).