Declining Survival of Lake Trout Stocked during 1963–1986 in U.S. Waters of Lake Superior

Hansen, Michael J.; Ebener, Mark P.; Schorfhaar, Richard G.; Schram, Stephen T.; Schreiner, Donald R.; Selgeby, James H.

doi:10.1577/1548-8675(1994)014<0395:dsolts>2.3.co;2

Cited by 23 publications

(14 citation statements)

References 11 publications

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“…Length and age data were compiled into age-length keys within years and management areas, which were then applied to the length frequency for the entire catch within each area and year to determine age composition (Ricker 1975). All stocked lake trout were marked by removal of one or more fins before stocking in Lake Superior, so scale ages of hatchery fish were validated by matching the fin clip observed on individual fish to the year-class in which that fin clip was used (Hansen et al 1994).…”

Section: Methodsmentioning

confidence: 99%

Recruitment Dynamics of the 1971–1991 Year‐Classes of Lake Trout in Michigan Waters of Lake Superior

Richards

Hansen

Bronte

et al. 2004

N American J Fish Manag

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In the 1950s, populations of lake trout Salvelinus namaycush in Lake Superior collapsed because of excessive exploitation and predation by sea lampreys Petromyzon marinus. Restoration began in the 1950s with the stocking of juvenile, hatchery‐reared lake trout and controls on fisheries and sea lampreys. Partial restoration was declared in 1996 because wild fish made up most of the populations in many areas, especially in Michigan waters, so stocking was dramatically curtailed in most areas. We evaluated the production of age‐7 lake trout (recruits) by age‐8 and older wild and stocked parental lake trout (spawners). Using Ricker stock–recruitment models, we also evaluated the effects of large‐mesh (114‐mm stretch measure) gill‐net effort on wild lake trout recruitment in Michigan waters of Lake Superior during 1970–1998. In general, the density of wild lake trout spawners increased, whereas that of stocked lake trout spawners decreased in all management areas investigated. The density of recruits was best described by the combined density of wild and stocked parents, which suggested similar reproductive contributions for both. Recruitment rates declined significantly with increasing spawner density in four of the five management areas and suggested that carrying capacities were reached and exceeded, which may serve as an indicator of population restoration. We conclude that both wild and stocked lake trout have contributed to the recruitment of lake trout in Michigan waters of Lake Superior. Large‐mesh gill‐net fishing effort varied in all Michigan management areas but did not account for the significant variation in wild lake trout recruitment. We conclude that levels of large‐mesh gill‐net fishing effort during 1970–1998 were not having an appreciable effect on wild lake trout recruitment in Michigan waters of Lake Superior.

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Section: Methodsmentioning

confidence: 99%

Recruitment Dynamics of the 1971–1991 Year‐Classes of Lake Trout in Michigan Waters of Lake Superior

Richards

Hansen

Bronte

et al. 2004

N American J Fish Manag

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“…Growth remained relatively constant during this population flux but decreased slightly in the late 1960s (Rahrer 1967;Pycha and King 1975). As rehabilitation progressed, annual survey data showed that abundance of wild lake trout increased (Hansen 1990;Hansen et al 1994a), although the parentage of wild lake trout was uncertain. Concurrently, abundance of stocked lake trout de-creased, despite relatively consistent stocking (Hansen et al 1994a(Hansen et al , 1994b.…”

Section: Recruitment Dynamics Of Lake Trout In Western Lakementioning

confidence: 99%

“…As rehabilitation progressed, annual survey data showed that abundance of wild lake trout increased (Hansen 1990;Hansen et al 1994a), although the parentage of wild lake trout was uncertain. Concurrently, abundance of stocked lake trout de-creased, despite relatively consistent stocking (Hansen et al 1994a(Hansen et al , 1994b. Early analyses of stock-recruit relationships showed that reproduction by stocked fish fueled wild fish recovery and that wild fish reproduction contributed little to that recovery (Hansen et al 1995a(Hansen et al , 1997.…”

Section: Recruitment Dynamics Of Lake Trout In Western Lakementioning

confidence: 99%

Recruitment Dynamics of Lake Trout in Western Lake Superior during 1988–1995

Corradin

Hansen

Schreiner

et al. 2008

N American J Fish Manag

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Stocks of lake trout Salvelinus namaycush in Lake Superior are recovering from historical collapse. Stocking, control of sea lampreys Petromyzon marinus, and harvest restrictions have aided lake trout recovery, but the contribution of stocked lake trout to contemporary recruitment has not been quantified in western Lake Superior. Using variants of the Ricker stock-recruit model, we evaluated the production of age-7 lake trout (recruits) by examining age-8 and older wild and stocked parental lake trout (spawners). We found that density of wild lake trout spawners and recruits increased during 1980-2003, whereas the density of stocked spawners decreased in all management areas. Two competing models best described recruit density of the 1988-2003 year-classes: (1) wild and stocked parents each contributed to recruitment but stocked parents contributed negatively and (2) only wild parents contributed to recruitment. Recruitment rates declined significantly with increasing spawner density in four of five management areas, which suggests that recruitment is density dependent in much of western Lake Superior. We conclude that stocked lake trout did not contribute significantly to lake trout rehabilitation in western Lake Superior during 1980-1995.

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“…We analyzed how some of these indices influenced the others, or were influenced by the rapid changes in the Lake Huron ecosystem, and how these indices influenced wild recruitment. In addition, we used the transition from a hatchery-dominated to a wild-dominated population in Lake Superior as a reference (Hansen et al 1994(Hansen et al , 1996Sitar and He 2006) to understand the potential time line of population recovery in Lake Huron.…”

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Lake Trout Status in the Main Basin of Lake Huron, 1973–2010

Ebener²,

Riley

et al. 2012

North American Journal of Fisheries Management

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We developed indices of lake trout Salvelinus namaycush status in the main basin of Lake Huron to understand increases in the relative abundance of wild year-classes during 1995-2010. Sea lamprey Petromyzon marinus wounds per 100 lake trout declined from 23.63 in 2000 to 5.86-10.64 in 2002-2010. The average age-7 lake trout catch per effort per recruitment (CPE/R; fish·305 m of gill net −1 ·million stocked yearlings −1 ) increased from 0.56 for the 1973-1990 year-classes to 0.92 for the 1991-2001 year-classes. Total CPE (fish/305 m of gill net) declined from 16.4 fish in 1996 to 4.1 fish in 2010, but the percentage of age-5 and younger lake trout steadily decreased from more than 70% before 1996 to less than 10% by 2009. The modal age in gill-net catches increased from age 5 before 1996 to age 7 by 2005. The average adult CPE increased from 2.8 fish/305 m of gill net during 1978-1995 to 5.34 fish/305 m of gill net during 1996-2010. The 1995-2010 year-classes of wild fish were more abundant than previous year-classes and were associated with the relatively high adult abundance during 1996-2010. Until the 2002 year-class, there was no decline in age-7 CPE/R; until 2008, there was no decline in adult CPE. Low survival of the 2002 and 2003 year-classes of stocked fish was related to the event of alewife Alosa pseudoharengus population collapse in 2003-2004. Lake trout in the main basin of Lake Huron are undergoing a transition from a hatchery stock to a wild stock, accompanied by *Corresponding author: hej@michigan.gov 402 LAKE TROUT STATUS IN LAKE HURON 403 an increased uncertainty in delayed recruitment. Future management should pay more attention to the protection of wild recruitment and the abundance of the spawning stock.

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Declining Survival of Lake Trout Stocked during 1963–1986 in U.S. Waters of Lake Superior

Cited by 23 publications

References 11 publications

Recruitment Dynamics of the 1971–1991 Year‐Classes of Lake Trout in Michigan Waters of Lake Superior

Recruitment Dynamics of the 1971–1991 Year‐Classes of Lake Trout in Michigan Waters of Lake Superior

Recruitment Dynamics of Lake Trout in Western Lake Superior during 1988–1995

Lake Trout Status in the Main Basin of Lake Huron, 1973–2010

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