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

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

doi:10.1577/1548-8659(1996)125<0831:codsol>2.3.co;2

Cited by 33 publications

(32 citation statements)

References 26 publications

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“…Our results may have differed from those of Hansen et al (1996) for several reasons. First, we analyzed the effect of fishing mortality on wild recruitment, whereas Hansen et al (1996) analyzed the effect of fishing mortality on stocked recruit- ment.…”

Section: Large-mesh Gill-net Effortcontrasting

confidence: 84%

“…Our results suggest that large-mesh gill-net fishing was not a significant factor limiting recruitment of the 1971-1991 year-classes of wild lake trout in five different areas of Michigan waters of Lake Superior, which contrasted to Hansen et al (1996), who found that large-mesh gill-net fishing effort was negatively related to recruitment of the 1963-1982 year-classes of stocked lake trout in Michigan and Wisconsin waters of Lake Superior. Our results may have differed from those of Hansen et al (1996) for several reasons.…”

Section: Large-mesh Gill-net Effortmentioning

confidence: 48%

“…Previously, Hansen et al (1996) found that declining density of stocked lake trout in Michigan waters was significantly associated with increasing large-mesh gill-net effort. Their analysis was based on the indexed survival of 1963-1982 yearclasses of stocked fish and, thus, did not reflect the effect of gill-net fishing effort on year-classes of wild lake trout that recruited after 1982.…”

Section: Please Scroll Down For Articlementioning

confidence: 99%

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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: Large-mesh Gill-net Effortcontrasting

confidence: 84%

Section: Large-mesh Gill-net Effortmentioning

confidence: 48%

Section: Please Scroll Down For Articlementioning

confidence: 99%

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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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“…Important foraging events may occur between sampling increments and not be evident in gut content samples. We simulated a situation in which native lake trout in Lake Superior were preying upon recently released hatchery lake trout fingerlings, a situation hypothesized by Hansen et al (1996) as a source of mortality for stocked lake trout. We used lake trout bioenergetics parameters of Stewart et al (1983), temperatures, diets, energy densities, starting weights, and ending weights described by Negus (1995), and δ 15 N and standard deviations measured by Harvey and Kitchell (2000).…”

Section: Model Applicationsmentioning

confidence: 99%

Using bioenergetics models to predict stable isotope ratios in fishes

Harvey¹,

Hanson²,

Essington³

et al. 2002

Can. J. Fish. Aquat. Sci.

105

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To describe temporal dynamics of stable isotope ratios in fishes, we developed a bioenergetics-based model that links isotope ratios to growth, as influenced by fish size, temperature, diet, and prey quality. The model includes error terms for isotope ratios, diet proportions, and fractionation. The model accurately predicted temporal δ 15 N dynamics of lake trout (Salvelinus namaycush) in a diet-switch experiment but was less successful for δ 13 C, possibly because of variable fractionation. The model was then used in three heuristic applications. In a diet-validation scenario, a model derived from limited knowledge of rainbow smelt (Osmerus mordax) diet reasonably estimated δ 13 C and δ 15 N compared with a null model but inaccurately estimated prey consumption. In a scenario where adult lake trout briefly cannibalized stocked lake trout fingerlings, the detectability of a cannibalism-induced δ 15 N increase depended on predator size, duration of cannibalism, and sample size. In a scenario where seasonal isotopic variability occurred at the base of a food web, variation propagated to higher trophic levels depended on consumer size and diet. Our approach is most valuable when used to examine multiple diet combinations that produce observed stable isotope ratios; one can then identify the most reasonable diets through field tests or other observations. Résumé : Dans le but de décrire la dynamique temporelle des rapports d'isotopes stables chez les poissons, nous avons mis au point un modèle basé sur la bioénergétique qui relie les rapports isotopiques à la croissance, elle-même influencée par la taille du poisson, la température, le régime alimentaire et la qualité des proies. Le modèle comprend des termes d'erreur pour les rapports isotopiques, les proportions du régime alimentaire et le fractionnement. Le modèle a permis de prédire avec précision la dynamique temporelle du δ 15 N chez le Touladi (Salvelinus namaycush) dans une expérience de changement de régime; il a été moins efficace dans la prédiction de δ 13 C, peut-être à cause du fractionnement variable. Le modèle a aussi servi dans trois applications heuristiques. Dans un scénario de validation du régime alimentaire, un modèle élaboré à partir d'une connaissance limitée du régime alimentaire de l'Éperlan arc-enciel (Osmerus mordax) a permis l'estimation adéquate de δ 13 C et de δ 15 N par rapport à un modèle nul, mais n'a pu déterminer correctement la consommation des proies. Dans un second scénario dans lequel des touladis se sont, pendant une courte période, alimentés par cannibalisme d'estivaux de touladis ensemencés, la possibilité de détection de l'augmentation de δ 15 N reliée au cannibalisme dépendait de la taille du prédateur, de la durée du cannibalisme et de la taille de l'échantillon. Dans un dernier scénario où la variation isotopique saisonnière se produisait à la base du réseau alimentaire, la variation qui se propageait aux niveaux trophiques supérieurs dépendait de la taille du consommateur et de son régime alimentaire. C'est dans l'exame...

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“…However, there are often many sources of fishing mortality that are unknown and not estimated (ICES, 2005). In the Laurentian Great Lakes, managers typically focus fishing mortality estimates on targeted fishing and sea lamprey (Petromyzon marinus) mortality (Hansen et al, 1996;Sitar et al, 1999). With few exceptions (i.e., some commercial fisheries targeting lake whitefish), commercial fishing discard or by-catch mortality remains poorly quantified throughout the Great Lakes.…”

Section: Introductionmentioning

confidence: 99%