Great Lakes Fishery Commission

Updated 2025-03-24 15:21:44

Lake Huron -> 1.0 Salmonine (Salmon and Trout) -> Lake Trout Abundance

1.2.1. Lake Trout relative abundance and stocking

The salmonine FCO for Lake Huron requires that Lake Trout be the dominant salmonine and calls for continued measurable progress towards Lake Trout rehabilitation.  Initiation of Sea Lamprey control in the St. Mary’s River beginning in 2000 and the subsequent collapse of Alewife populations in 2003 facilitated the start of Lake Trout recovery in Michigan waters as evidenced by a significant increase in wild recruits starting in 2009.  Additional evidence of progress toward Lake Trout recovery in Michigan waters includes increased reproductive potential of current stocks, continued wild recruitment that has resulted in the establishment of wild spawning stock, and elimination of reproductive impairments that was attributable to thiaminase-enriched diet (Ebener 1998).

In Michigan waters, adult Lake Trout relative abundance peaked in 2000 and declined to about the 1980s level during current reporting period (Figure 1).   Catch of juvenile Lake Trout (stocked + wild) in Michigan Department of Natural Resources spring gill net surveys has remained under 20% since 2002, except during 2014-15 (Figure 2).  However, the percentage of wild juveniles, has increased over five-fold since the early 2000s and remained near all-time highs in the current reporting period (Figure 2).

As in Michigan waters, Sea lamprey control in the St. Mary’s River since 1997 (Criger et al., 2021) and the subsequent collapse of alewife populations in 2003 (He, 2024) facilitated a significant recovery of wild Lake Trout in Ontario waters of Lake Huron. However, there is a great deal of variably between lake trout populations in Ontario waters and indicators are often not being fully met.

Since only two small remnant lake trout populations survived early sea lamprey invasion in Lake Huron, pure strain Lake Trout began to be planted in Ontario waters in 1977 and stocking increased significantly during the 1990s (Figure 3). Stocking in the main basin stopped in 2015 but continues to occur in the North Channel and Georgian Bay.

Relative abundance target range for Lake Trout on spawning grounds in Ontario waters is 17 to 135 adult fish per 305 m (1000 ft) of gillnet.  It is expected that spawning populations initially will be comprised of hatchery-reared fish but progressively shift towards wild stocks. The highest spawner catch-per-unit-effort (CPUE) in Ontario is in Georgian Bay, where populations are comprised of a majority of hatchery-origin fish (Figure 4). None of the basins have met the minimum spawning fish CPUE threshold for wild fish. However, limited spawning surveys have occurred in the main basin.

Relative abundance (catch-per-unit-effort) of adult Lake Trout determined from annual spring gillnet surveys conducted by the Michigan Department of Natural Resources in Michigan waters of Lake Huron (depth range: 10-60 m), 1970-2024.

Relative frequency (percent) of juvenile Lake Trout in annual spring gillnet surveys conducted by the Michigan Department of Natural Resources in Michigan waters of Lake Huron (depth range: 10-60 m), 1970-2024.

Number (millions) of yearling equivalent Lake Trout stocked into Ontario waters of Lake Huron by basin, 1969-2022.

Catch-per-unit-effort of spawning Lake Trout (number per 305 m of standard index gillnet) by survey area and basin (Georgian Bay: GB, the North Channel: NC, and the northern main basin: NMB). No spawner surveys occur in the southern main basin. Horizontal line corresponds to the minimum indicator threshold (17 spawners per 305 m of gillnet) recommended in Ebener (1998).