Consequences of prey fish community dynamics on lake trout (Salvelinus namaycush) foraging efficiency in Lake Superior

We used a size-structured model, indexed by age, that combines bioenergetics and foraging theory to evaluate the effects of prey fish community structure (species dominance, size structure, and density) on the diet and net foraging efficiency of lake trout (Salvelinus namaycush) in Lake Superior. Prey size structure was important for young lake trout but decreased in importance for older lake trout, especially with increasing prey density. The model predicted that rainbow smelt (Osmerus mordax) should dominate the diet of young lake trout due to the size-dependent capture limitations of larger prey. In contrast, lake herring (Coregonus artedi) should dominate the diet of oldest lake trout owing to a higher net energy return than rainbow smelt. Model results are consistent with age-specific diet and size-at-age of lake trout during the last 40 years. Diets of intermediate-sized lake trout do not reflect the recent resurgence of lake herring populations. Absence of a dietary switch is probably due to higher capture probability for rainbow smelt. Lake trout growth and production will likely be highest with a mixed prey species assemblage of young rainbow smelt and older lake herring.

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Changes in the Zoobenthos Community of Acidified Bowland Lake after Whole-Lake Neutralization and Lake Trout (Salvelinus namaycush) Reintroduction

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f90-047 ◽

1990 ◽

Vol 47 (2) ◽

pp. 440-445 ◽

Cited By ~ 14

Author(s):

W. Keller ◽

Lewis A. Molot ◽

Ronald W. Griffiths ◽

N. D. Yan

Keyword(s):

Water Quality ◽

Fish Community ◽

Lake Trout ◽

Size Structure ◽

Salvelinus Namaycush ◽

Total Abundance ◽

Insufficient Time

The zoobenthos of Bowland Lake is described prior to, and for 2 yr after, neutralization of the lake from pH 4.9 to > 6.0 and reintroduction of lake trout (Salvelinus namaycush). Observed changes in the total abundance, biomass, and size structure of shallow and profundal zoobenthos assemblages were attributable to changes in the fish community, not to improvements in water quality. A shift toward increased importance of oligochaetes, more representative of nonacidic conditions, occurred. However, many common, acid-sensitive taxa of zoobenthos which were absent prior to neutralization had not appeared within 2 yr after treatment, indicating insufficient time for recolonization.

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A stable isotope evaluation of the structure and spatial heterogeneity of a Lake Superior food web

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f00-072 ◽

2000 ◽

Vol 57 (7) ◽

pp. 1395-1403 ◽

Cited By ~ 58

Author(s):

Chris J Harvey ◽

James F Kitchell

Keyword(s):

Stable Isotope ◽

Spatial Heterogeneity ◽

Food Web ◽

Lake Trout ◽

Trophic Position ◽

Lake Superior ◽

Salvelinus Namaycush ◽

Trophic Relationships ◽

Rainbow Smelt ◽

Western Lake

We used stable isotope analysis to derive trophic relationships and movement patterns for components of the western Lake Superior food web. Trophic linkages implied by previous gut content studies were only marginally supported by stable isotope data. Siscowet lake trout (Salvelinus namaycush siscowet) were the top predators, and trophic overlap between siscowet and lean lake trout (Salvelinus namaycush) was low. Exotic Pacific salmon (Oncorhynchus spp.) occupied a lower trophic position than native piscivores because the latter relied more on coregonids. To evaluate spatial heterogeneity of the food web, we assumed that the adjacent cities of Duluth and Superior (DS) were a point source of 15N, and we measured isotopes of organisms close to and far from DS. Slimy sculpin (Cottus cognatus) were enriched in the DS area relative to other sites, implying that they are relatively sedentary. Rainbow smelt (Osmerus mordax) showed no differences at any sites, implying high vagility. Other organisms showed differences that could not be attributed to DS, implying that other mechanisms, such as trophic ontogeny, were influencing their isotopic signatures.

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Lake Superior Revisited 1984

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f87-306 ◽

1987 ◽

Vol 44 (S2) ◽

pp. s23-s36 ◽

Cited By ~ 30

Author(s):

Wayne R. MacCallum ◽

James H. Selgeby

Keyword(s):

Fish Community ◽

Lake Trout ◽

Pacific Salmon ◽

Lake Superior ◽

Sea Lamprey ◽

Osmerus Mordax ◽

Coregonus Clupeaformis ◽

Rainbow Smelt ◽

Coregonus Artedii ◽

Historical Levels

The Lake Superior fish community has changed substantially since the early 1960s, when control of the sea lamprey (Petromyzon marinus) became effective. Self-reproducing stocks of lake trout (Salvelinus namaycush) have been reestablished in many inshore areas, although they have not yet reached pre-sea lamprey abundance; offshore lake trout are probably at or near pre-sea lamprey abundance. Stocks of lake whitefish (Coregonus clupeaformis) appear to have fully recovered; commercial catches are at or above historical levels. Lake herring (Coregonus artedii) are recovering rapidly in U.S. waters and are abundant in western Canadian waters. The population of rainbow smelt (Osmerus mordax), which declined in the 1970s, is recovering. Pacific salmon (Oncorhynchus) are becoming more abundant as a result of increased stocking in U.S. waters and are reproducing in most suitable tributaries; they have become significant in anglers' creels.

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Successional Change in the Lake Superior Fish Community: Population Trends in Ciscoes, Rainbow Smelt, and Lake Trout, 1958--2008

Advances in Limnology ◽

10.1127/advlim/63/2012/337 ◽

2012 ◽

Vol 63 ◽

pp. 337-362

Author(s):

O.T. Gorman

Keyword(s):

Fish Community ◽

Lake Trout ◽

Lake Superior ◽

Population Trends ◽

Rainbow Smelt ◽

Community Population ◽

Successional Change

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Size Structure of a Lake Trout (Salvelinus namaycush) Population an Arctic Lake: Influence of Angling and Implications for Fish Community Structure

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f89-266 ◽

1989 ◽

Vol 46 (12) ◽

pp. 2153-2156 ◽

Cited By ~ 22

Author(s):

Michael E. McDonald ◽

Anne E. Hershey

Keyword(s):

Community Structure ◽

Fish Community ◽

Lake Trout ◽

Size Structure ◽

Salvelinus Namaycush ◽

Fish Community Structure ◽

Median Length ◽

Arctic Alaska ◽

Gill Net ◽

Toolik Lake

The lake trout (Salvelinus namaycush) population in Toolik Lake in arctic Alaska was assessed by gill net during 1977, prior to exploitation. In 1986 we replicated the gill net study to determine the effects of recent angling pressure on the fish community. Relative composition of the catch varied between samples. Round whitefish (Prosopium cylindraceum), which are not susceptible to angling, made up 42% of the catch in 1986 and 28% in 1977. Significant reductions in the median length and weight of lake trout between the sampling periods were observed. The median size of lake trout in 1986 was below the minimum 1977 reproductive size. Differences in median length and weight of grayling (Thymallus arcticus) and of round whitefish during this period were not significantly different. The condition factor of lake trout was significantly higher in 1986. We suggest that large lake trout in Toolik Lake control salmonid recruitment and determine community structure. With continued fishing pressure further changes in the fish community and lake trophic dynamics may result.

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Fish community change in Lake Superior, 1970–2000

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f03-136 ◽

2003 ◽

Vol 60 (12) ◽

pp. 1552-1574 ◽

Cited By ~ 136

Author(s):

Charles R Bronte ◽

Mark P Ebener ◽

Donald R Schreiner ◽

David S DeVault ◽

Michael M Petzold ◽

...

Keyword(s):

Great Lakes ◽

Native Species ◽

Fish Community ◽

Lake Trout ◽

Community Change ◽

Osmerus Mordax ◽

Rainbow Smelt ◽

Additional Species ◽

Community Agencies ◽

Natural Reproduction

Changes in Lake Superior's fish community are reviewed from 1970 to 2000. Lake trout (Salvelinus namaycush) and lake whitefish (Coregonus clupeaformis) stocks have increased substantially and may be approaching ancestral states. Lake herring (Coregonus artedi) have also recovered, but under sporadic recruitment. Contaminant levels have declined and are in equilibrium with inputs, but toxaphene levels are higher than in all other Great Lakes. Sea lamprey (Petromyzon marinus) control, harvest limits, and stocking fostered recoveries of lake trout and allowed establishment of small nonnative salmonine populations. Natural reproduction supports most salmonine populations, therefore further stocking is not required. Nonnative salmonines will likely remain minor components of the fish community. Forage biomass has shifted from exotic rainbow smelt (Osmerus mordax) to native species, and high predation may prevent their recovery. Introductions of exotics have increased and threaten the recovering fish community. Agencies have little influence on the abundance of forage fish or the major predator, siscowet lake trout, and must now focus on habitat protection and enhancement in nearshore areas and prevent additional species introductions to further restoration. Persistence of Lake Superior's native deepwater species is in contrast to other Great Lakes where restoration will be difficult in the absence of these ecologically important fishes.

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Survey of the Genetic Variation Among Eastern Lake Superior Lake Trout (Salvelinus namaycush)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f81-222 ◽

1981 ◽

Vol 38 (12) ◽

pp. 1738-1746 ◽

Cited By ~ 24

Author(s):

Terrence R. Dehring ◽

Anne F. Brown ◽

Charles H. Daugherty ◽

Stevan R. Phelps

Keyword(s):

Genetic Variation ◽

Gel Electrophoresis ◽

Lake Trout ◽

Lake Superior ◽

Salvelinus Namaycush ◽

Starch Gel Electrophoresis ◽

Average Heterozygosity ◽

Management Implications ◽

Salmonid Species ◽

Starch Gel

Patterns of genetic variation among lake trout (Salvelinus namaycush) of eastern Lake Superior were examined using starch gel electrophoresis. We used 484 individuals sampled from three areas, representing three morphological types (leans, humpers, and siscowets). Of 50 loci examined, 44 were monomorphic in all groups sampled. Genetic variation occurs at six loci AAT-1,2, MDH-3,4, ME-1, and SOD-1. The average heterozygosity found (H = 0.015) is low relative to other salmonid species. A significant amount of heterogeneity exists among the 10 lake trout samples. These differences are due to variation within as well as between morphological types. The significance and management implications of these data are discussed.Key words: genetic variation, lake trout, Salvelinus namaycush, Lake Superior

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Sea lamprey (Petromyzon marinus) size trends in a salmonid stocking context in Lake Superior

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f05-145 ◽

2005 ◽

Vol 62 (10) ◽

pp. 2354-2361 ◽

Cited By ~ 4

Author(s):

Jeffrey C Jorgensen ◽

James F Kitchell

Keyword(s):

Bayesian Model ◽

Fish Community ◽

Bayesian Model Averaging ◽

Lake Trout ◽

Pacific Salmon ◽

Lake Superior ◽

Petromyzon Marinus ◽

Control Period ◽

Model Averaging ◽

Sea Lamprey

Fish community objectives for Lake Superior call for restoration such that it resembles its historical species composition, to the extent possible, yet allow for supplementation of naturalized Pacific salmonids (Oncorhynchus spp.). To achieve these goals, managers strive to control the sea lamprey (Petromyzon marinus) to levels that cause insignificant (<5%) mortality to host species. While control efforts have been successful, sea lamprey size has increased during the control period. We analyzed long-term sea lamprey size trends and found a significant increase from 1961 to 2003 (F = 36.76, p < 0.001, R2 = 0.473). A local regression revealed two significant size increase periods. We used Bayesian model averaging to find the relationship between sea lamprey size and the stocking of salmonids (lean lake trout (Salvelinus namaycush) and Pacific salmon). Bayesian model averaging identified 91 models, and several regressors were common features in many of the models. Sea lamprey weight was related to stocked lake trout lagged 3, 9, 11, and 13 years, and stocked Pacific salmon lagged 4 years. If sea lampreys can achieve larger sizes attached to Pacific salmonid hosts, and thus inflict more damage, there may be a trade-off for managers in achieving the fish community objectives for Lake Superior.

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