Lake Michigan's Capacity to Support Lake Trout (Salvelinus namaycush) and Other Salmonines: An Estimate Based on the Status of Prey Populations in the 1970s

1985 ◽  
Vol 42 (3) ◽  
pp. 449-454 ◽  
Author(s):  
G. W. Eck ◽  
Edward H. Brown Jr.
Keyword(s):  
Lake Michigan ◽  
Lake Trout ◽  
Physiological Stress ◽  
Total Mortality ◽  
Salvelinus Namaycush ◽  
Predatory Fish ◽  
Natural Mortality ◽  
Alosa Pseudoharengus ◽  
Mass Balance Equation ◽  
The Status

We used a mass balance equation relating total mortality of age II and older alewives (Alosa pseudoharengus) to their removals by predatory fish and other sources of mortality as the basis for estimating that the forage base in Lake Michigan could support an additional 13 000 to 21 000 t of lake trout (Salvelinus namaycush) or a total lake trout biomass between 15 000 and 23 000 t. This biomass estimate is projected with biomasses of other trout and salmon held at 1979 levels. Major premises of this approach are that (1) the sustained availability of age II and older alewives to salmonines will ultimately limit the expansion of salmonine stocks, (2) the alewife population was oscillating without trend during 1973–80, and (3) additional limited predation on alewives would be compensated by a reduction in natural mortality caused by physiological stress and disease.

An Energetics Model for Lake Trout, Salvelinus namaycush: Application to the Lake Michigan Population

1983 ◽  
Vol 40 (6) ◽  
pp. 681-698 ◽  
Author(s):  
Donald J. Stewart ◽  
David Weininger ◽  
Donald V. Rottiers ◽  
Thomas A. Edsall
Keyword(s):  
Lake Michigan ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
High Energy ◽  
Alosa Pseudoharengus ◽  
Fishing Mortality ◽  
Age Classes ◽  
Short Term ◽  
Conversion Efficiencies

An energetics model is implemented for lake trout, Salvelinus namaycush, and applied to the Lake Michigan population. It includes an egestion function allowing any proportional mix of fish and invertebrates in the diet, a growth model accounting for both ontogenetic and seasonal changes in energy-density of predator and prey, a model for typical in situ swimming speed, and reproductive energy losses due to gametes shed. Gross conversion efficiency of energy by lake trout over their life (21.8%) is about twice the efficiency of converting biomass to growth because they store large amounts of high-energy fats. Highest conversion efficiencies are obtained by relatively fast-growing individuals, and over half the annual energy assimilated by older age-classes may be shed as gametes. Sensitivity analysis indicates a general robustness of the model, especially for estimating consumption by fitting a known growth curve. Largest sensitivities were for the intercept and weight dependence coefficients of metabolism. Population biomass and associated predatory impact of a given cohort increase steadily for about 3.5 yr then decline steadily after fishing mortality becomes important in the fourth year in the lake. This slow response time precludes manipulation of lake trout stocking densities as a means to control short-term prey fluctuations. Predation by lake trout on alewife, Alosa pseudoharengus, has been increasing steadily since 1965 to about 8 400 t∙yr−1, and is projected to rise to almost 12 000 t∙yr−1 by 1990.

Population Biology of Lake Trout (Salvelinus namaycush) of Lake Superior before 1950

1971 ◽  
Vol 28 (1) ◽  
pp. 65-71 ◽  
Author(s):  
Gary T. Sakagawa ◽  
Richard L. Pycha
Keyword(s):  
Mortality Rate ◽  
Population Biology ◽  
Lake Trout ◽  
Lake Superior ◽  
Indirect Evidence ◽  
Total Mortality ◽  
Growth Yield ◽  
Salvelinus Namaycush ◽  
Natural Mortality ◽  
Trout Population

Scale samples collected in 1948 were used to estimate the instantaneous total mortality rate (0.70) and growth for lake trout (Salvelinus namaycush) in Lake Superior before the population had been significantly reduced by the sea lamprey (Petromyzon marinus). Indirect evidence indicates that the instantaneous natural mortality rate was probably 0.10–0.25. The Ricker model was used to calculate yield per recruitment, which varied with natural mortality and growth. Natural mortality was more critical than growth; yield per recruitment increased 183.3% with a 60% decrease in instantaneous natural mortality (from 0.25 to 0.10). For the prelamprey lake trout population the yield per recruitment was about 12–34 lb; the recruitment of about 3.6–10.1 million lake trout of age 1.5 resulted in an annual commercial production of 4 million lb.

An examination of the PCB: lipid relationship among individual fish

1997 ◽  
Vol 54 (5) ◽  
pp. 1031-1038
Author(s):  
C A Stow ◽  
L J Jackson ◽  
J F Amrhein
Keyword(s):  
Salmo Trutta ◽  
Lake Michigan ◽  
Oncorhynchus Tshawytscha ◽  
Lake Trout ◽  
Coho Salmon ◽  
Salvelinus Namaycush ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Strong Linear Correlation ◽  
Brown Trout Salmo Trutta ◽  
The Relationship

We examined data from 1984 to 1994 for five species of Lake Michigan salmonids to explore the relationship between total PCB concentration and percent lipid. When we compared mean species lipid and PCB values, we found a strong linear correlation. When we compared values among individuals, we found modest positive PCB:lipid associations in brown trout (Salmo trutta), chinook salmon (Oncorhynchus tshawytscha), coho salmon (Oncorhynchus kisutch), and rainbow trout (Oncorhynchus mykiss) collected during spawning, but positive associations were not apparent among nonspawning individuals. Lake trout (Salvelinus namaycush) exhibited no discernible PCB:lipid relationship. Our results are not incompatible with previous observations that contaminants are differentially partitioned into lipids within a fish, but these results do suggest that lipids are not a major factor influencing contaminant uptake.

Optimal Use of Creel Survey Data in Assessing Population Behaviour: Lake Opeongo Lake Trout (Salvelinus namaycush) and Smallmouth Bass (Micropterus dolomieui), 1936–83

1987 ◽  
Vol 44 (S2) ◽  
pp. s229-s238 ◽  
Author(s):  
B. J. Shuter ◽  
J. E. Matuszek ◽  
H. A. Regier
Keyword(s):  
Lake Trout ◽  
Total Mortality ◽  
Salvelinus Namaycush ◽  
Fish Population ◽  
Smallmouth Bass ◽  
Fishing Mortality ◽  
Assessment Data ◽  
Creel Survey ◽  
Micropterus Dolomieui ◽  
Independent Assessment

Creel survey and independent assessment data on the lake trout (Salvelinus namaycush) and smallmouth bass (Micropterus dolomieui) populations of Lake Opeongo were evaluated. Annual estimates of total mortality, fishing mortality, and abundance were generated for each population over the period 1936–83. Large variations in survey efficiency, angler efficiency, fishing mortality, and abundance were identified over this period. We argue that a creel survey, which is expected to provide reliable information on fish population dynamics, requires an overall study design which includes collection of data on the number and relative efficiency of different kinds of anglers and periodic assessment studies aimed at providing independent checks on both survey effectiveness and population behaviour.

New abbreviated calculation for measuring intrinsic rebound potential in exploited fish populations — example for sharks

2015 ◽  
Vol 72 (5) ◽  
pp. 767-773 ◽  
Author(s):  
David W. Au ◽  
Susan E. Smith ◽  
Christina Show
Keyword(s):  
Life Histories ◽  
Full Range ◽  
Total Mortality ◽  
Fish Populations ◽  
Natural Mortality ◽  
Age At Maturity ◽  
Contour Pattern ◽  
The Status

Intrinsic rebound potential, the demographic measure of a fish population’s productivity that sustains a given mortality, relates to a species’ resiliency and can be useful for understanding and evaluating the status of exploited populations, especially those poorly monitored and of low productivity, like many shark populations. The rebound potential is derived from the Euler–Lotka equation and, with the dynamics kept simple, is easily calculated for a given total mortality, needing only a species’ age at maturity and its natural mortality (M). Its value can be quickly read from an isopleth diagram, whose contour pattern shows the interdependence of these two key parameters among different life histories. How the rebound potentials change as a function of age at maturity and the full range of possible M values also shows a way to estimate a species’ natural mortality bounds. Importance of the age at maturity parameter is stressed.

scholarly journals Mercury source changes and food web shifts alter contamination signatures of predatory fish from Lake Michigan

2019 ◽  
Vol 116 (47) ◽  
pp. 23600-23608 ◽  
Author(s):  
Ryan F. Lepak ◽  
Joel C. Hoffman ◽  
Sarah E. Janssen ◽  
David P. Krabbenhoft ◽  
Jacob M. Ogorek ◽  
...  
Keyword(s):  
Invasive Species ◽  
Great Lakes ◽  
Food Web ◽  
Lake Michigan ◽  
Lake Trout ◽  
Mitigation Strategies ◽  
Predatory Fish ◽  
Isotopic Analyses ◽  
C And N ◽  
The Impact

To understand the impact reduced mercury (Hg) loading and invasive species have had on methylmercury bioaccumulation in predator fish of Lake Michigan, we reconstructed bioaccumulation trends from a fish archive (1978 to 2012). By measuring fish Hg stable isotope ratios, we related temporal changes in Hg concentrations to varying Hg sources. Additionally, dietary tracers were necessary to identify food web influences. Through combined Hg, C, and N stable isotopic analyses, we were able to differentiate between a shift in Hg sources to fish and periods when energetic transitions (from dreissenid mussels) led to the assimilation of contrasting Hg pools (2000 to present). In the late 1980s, lake trout δ202Hg increased (0.4‰) from regulatory reductions in regional Hg emissions. After 2000, C and N isotopes ratios revealed altered food web pathways, resulting in a benthic energetic shift and changes to Hg bioaccumulation. Continued increases in δ202Hg indicate fish are responding to several United States mercury emission mitigation strategies that were initiated circa 1990 and continued through the 2011 promulgation of the Mercury and Air Toxics Standards rule. Unlike archives of sediments, this fish archive tracks Hg sources susceptible to bioaccumulation in Great Lakes fisheries. Analysis reveals that trends in fish Hg concentrations can be substantially affected by shifts in trophic structure and dietary preferences initiated by invasive species in the Great Lakes. This does not diminish the benefits of declining emissions over this period, as fish Hg concentrations would have been higher without these actions.

Bioenergetics and PCB, DDE, and Mercury Dynamics in Lake Ontario Lake Trout (Salvelinus namaycush): A Model based on Surveillance Data

1992 ◽  
Vol 49 (6) ◽  
pp. 1086-1096 ◽  
Author(s):  
U. Borgmann ◽  
D. M. Whittle
Keyword(s):  
Gastrointestinal Tract ◽  
Lake Trout ◽  
Prey Selection ◽  
Lake Ontario ◽  
Salvelinus Namaycush ◽  
Whole Body ◽  
Alosa Pseudoharengus ◽  
Assimilation Rate ◽  
Feeding Rates ◽  
Dynamics Model

Lake trout (Salvelinus namaycush) ingestion rates in a bioenergetics and contaminant dynamics model were estimated directly from contaminant concentrations in lake trout and their prey, rather than from the sum of growth and predicted metabolism. Elimination rates for PCB and DDE, but not for mercury, were dependent on either body mass or lipid content. Concentrations in lake trout responded rapidly to changes in concentration of their prey. This was due primarily to growth dilution and not contaminant elimination, especially for DDE and PCB. Changes in lipid concentrations, therefore, have only minor effects on final concentrations in lake trout, and it is not appropriate to lipid normalize PCB or DDE concentrations when examining trends in whole-body concentrations for this species. Concentrations of PCBs and lipids have declined in lake trout from 1977 to 1988. The drop in PCB concentrations is probably not caused primarily by the lowered lipid concentrations but is the result of either a reduction in feeding rates and improved growth efficiencies, a reduction in PCB concentrations in alewife (Alosa pseudoharengus), or an undocumented change in prey selection. Models based on chemical kinetics across the gastrointestinal tract are more consistent with observed data than models based on a constant contaminant assimilation rate and direct excretion.

Recent Changes in Lake Michigan's Fish Community and Their Probable Causes, With Emphasis on the Role of the Alewife (Alosa pseudoharengus)

1987 ◽  
Vol 44 (S2) ◽  
pp. s53-s60 ◽  
Author(s):  
Gary W. Eck ◽  
Larue Wells
Keyword(s):  
Native Species ◽  
Yellow Perch ◽  
Gasterosteus Aculeatus ◽  
Lake Michigan ◽  
Lake Trout ◽  
Pink Salmon ◽  
Oncorhynchus Gorbuscha ◽  
Alosa Pseudoharengus ◽  
Poor Recruitment ◽  
Emerald Shiner

Major changes in fish populations occurred in Lake Michigan between the early 1970s and 1984. The abundance of lake trout (Salvelinus namaycush) and several nonnative species of salmonines increased greatly as a result of intensive stocking. The exotic alewife (Alosa pseudoharengus), which had proliferated to extremely high levels of abundance in the mid-1960s, declined, particularly in the early 1980s. We believe that the sharp decline in alewives in the 1980s was caused primarily by poor recruitment during the colder than normal years of 1976–82. Several of Lake Michigan's endemic species of fish appeared to be adversely affected by alewives: bloater (Coregonus hoyi), lake herring (C. artedii), emerald shiner (Notropis atherinoides), yellow perch (Perca flavescens), and deepwater sculpin (Myoxocephalus thompsoni), and possibly spoonhead sculpin (Cottus ricei). All declined when alewives were abundant, and those that did not become rare, i.e. the bloater, perch, and deepwater sculpin recovered when alewives declined. We present evidence suggesting that the mechanism by which alewives affect native species is not by competition for food, as has often been hypothesized, and discuss the possibility that it is predation on early life stages. Despite the decreased availability of alewives in the early 1980s, salmonines continued to eat mainly alewives. The highly abundant alternate prey species were eaten only sparingly, but alewives still may have been abundant enough to meet the forage requirements of salmonines. Two new exotics, the pink salmon (Oncorhynchus gorbuscha) and threespine stickleback (Gasterosteus aculeatus), increased in abundance in the 1980s, and could become detrimental (particularly the salmon) to other species.

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