Responses of Lake Trout (Salvelinus namaycush) to Harvesting, Stocking, and Lamprey Reduction

1980 ◽  
Vol 37 (11) ◽  
pp. 2133-2145 ◽  
Author(s):  
Carl J. Walters ◽  
Greg Steer ◽  
George Spangler
Keyword(s):  
Simple Model ◽  
Policy Analysis ◽  
Great Lakes ◽  
Population Regulation ◽  
Lake Trout ◽  
Normal Population ◽  
Lake Superior ◽  
Sea Lamprey ◽  
Salvelinus Namaycush ◽  
Density Dependent

Sustained yields, declines, and recovery of lake trout (Salvelinus namaycush) can be explained by a simple model that hypothesizes normal population regulation through density dependent body growth, coupled with depensatory lamprey mortality. The model indicates that either lamprey or fishing alone could have caused the Lake Superior decline, though they apparently operated in concert. The presence of depensatory lamprey mortality leads to a "cliff edge" in the system's dynamics, such that catastrophic changes may be repeated in the future. It is not unlikely that Lake Superior is on the verge of a second collapse. Options for dealing with potential disasters include conservative harvesting policies, development of more sensitive monitoring indicators, and modified stocking policies that may speed the coevolution of a viable lamprey/trout association.Key words: lake trout, sea lamprey, simulation, Great Lakes, policy analysis

Classification of Sea Lamprey (Petromyzon marinus) Attack Marks on Great Lakes Lake Trout (Salvelinus namaycush)

1980 ◽  
Vol 37 (11) ◽  
pp. 1989-2006 ◽  
Author(s):  
Everett Louis King Jr.
Keyword(s):  
Great Lakes ◽  
Lake Trout ◽  
Petromyzon Marinus ◽  
Attachment Site ◽  
Sea Lamprey ◽  
Salvelinus Namaycush ◽  
Oral Disc ◽  
Field Assessment ◽  
Sea Lampreys

Criteria for the classification of marks inflicted by sea lamprey (Petromyzon marinus) into nine categories were developed from laboratory studies in an attempt to refine the classification system used in field assessment work. These criteria were based on characteristics of the attachment site that could be identified under field conditions by unaided visual means and by touching the attachment site. Healing of these marks was somewhat variable and was influenced by the size of lamprey, duration of attachment, severity of the wound at lamprey detachment, season and water temperature, and by other less obvious factors. Even under laboratory conditions staging of some wounds was difficult, especially at low water temperatures. If these criteria are to be used effectively and with precision in the field, close examination of individual fish may be required. If the feeding and density of specific year-classes of sea lampreys are to be accurately assessed on an annual basis, close attention to the wound size (as it reflects the size of the lamprey's oral disc) and character of wounds on fish will be required as well as consideration of the season of the year in which they are observed.Key words: sea lamprey, attack marks, lake trout, Great Lakes

On Evaluating Measures to Rehabilitate Lake Trout (Salvelinus namaycush) of Lake Superior

1980 ◽  
Vol 37 (11) ◽  
pp. 2057-2062 ◽  
Author(s):  
A. H. Lawrie ◽  
W. MacCallum
Keyword(s):  
Lake Trout ◽  
Lake Superior ◽  
Petromyzon Marinus ◽  
Control Program ◽  
Mortality Rates ◽  
Sea Lamprey ◽  
Salvelinus Namaycush ◽  
Planting Density ◽  
Hatchery Fish ◽  
Natural Recruitment

The Lake Superior lake trout (Salvelinus namaycush) population is being rebuilt following its collapse in the early 1950s. Estimates are presented of the contributions to this recovery provided directly by the artificial recruitment of hatchery fish, a demonstrable amelioration in mortality rates and a resurgence, lately, of natural recruitment. Of the increased lake trout abundance, 55% on the average was owing to trebling the planting density, 40% to improved survival, and 5% to increasing recruitment of native lake trout. The precise contribution of the sea lamprey (Petromyzon marinus) control program could not be defined for lack of sufficient early data.Key words: lake trout, sea lamprey, rehabilitation, natural recruitment, hatchery stocking

Changes in Mortality of Lake Trout (Salvelinus namaycush) in Michigan Waters of Lake Superior in Relation to Sea Lamprey (Petromyzon marinus) Predation, 1968–78

1980 ◽  
Vol 37 (11) ◽  
pp. 2063-2073 ◽  
Author(s):  
Richard L. Pycha
Keyword(s):  
Fishery Management ◽  
Lake Trout ◽  
Lake Superior ◽  
Petromyzon Marinus ◽  
Total Mortality ◽  
Sea Lamprey ◽  
Salvelinus Namaycush ◽  
Catch Per Unit Effort ◽  
Instantaneous Rate ◽  
Unit Effort

Total mortality rates of lake trout (Salvelinus namaycush) of age VII and older from eastern Lake Superior were estimated from catch curves of age distributions each year in 1968–78. The instantaneous rate of total mortality Z varied from 0.62 to 2.31 in close synchrony with sea lamprey (Petromyzon marinus) wounding rates on lake trout. The regression of transformed Z on the index of lamprey wounding, accounted for over 89% of the variation in lake trout mortality (r2 = 0.893). An iterative method of estimating rates of exploitation u, instantaneous rates of fishing mortality F, K (a constant relating sample catch per unit effort to population size), instantaneous normal natural mortality rate M, and instantaneous rate of mortality due to sea lamprey predation L from the sample catch per unit effort and total catch by the fishery is presented. A second method using the results of a 1970–71 tagging study to estimate the mean F in 1970–77 yielded closely similar results to the above and is presented as corroboration. The estimates of u, F, and M appear to be reasonable. F ranged from 0.17 in 1974 to 0.42 in 1969 and M was estimated at 0.26. L varied from 0.21 in 1974 to 1.70 in 1968. Management implications of various policies concerning sea lamprey control, exploitation, and stocking are discussed.Key words: lake trout, sea lamprey, lamprey control, mortality, predation, Lake Superior, fishery, management

Decline and Recovery of the Lake Superior Gull Island Reef Lake Trout (Salvelinus namaycush) Population and the Role of Sea Lamprey (Petromyzon marinus) Predation

1980 ◽  
Vol 37 (11) ◽  
pp. 2074-2080 ◽  
Author(s):  
Bruce L. Swanson ◽  
Donald V. Swedberg
Keyword(s):  
Lake Trout ◽  
Lake Superior ◽  
Petromyzon Marinus ◽  
Total Mortality ◽  
Mortality Rates ◽  
Sea Lamprey ◽  
Salvelinus Namaycush ◽  
Steady Increase ◽  
Egg Deposition

The Gull Island Reef lake trout (Salvelinus namaycush) population was one of the few in Lake Superior that was not annihilated by the combined effects of excessive fishing and sea lamprey (Petromyzon marinus) predation. Following control of the lamprey in the early 1960s, this population of lake trout began a slow but steady increase in the average age and numbers of lake trout. Total annual mortality rates for spawning lake trout were 32% for age VI fish, 48% for ages VII–VIII, and 75% for ages IX and older. These total mortality rates included a 7.3% exploitation rate u, a 20% natural mortality n, and annual lamprey-induced mortalities of 6% for ages V–VI, 24%, for ages VII–VIII, and 56% for ages IX and older fish. The estimated number of lake trout eggs deposited annually on Gull Island Reef from 1964 to 1979 ranged from 3.3 million eggs in 1965 to 28 million eggs in 1979, with a mean of 9 million eggs per year. At present levels of lamprey predation, the estimated egg to spawning fish return rate on Gull Island Reef is 0.18%.Key words: lake trout, sea lamprey, survival, population structure, egg deposition

Larkin's Predation Model of Lake Trout (Salvelinus namaycush) Extinction with Harvesting and Sea Lamprey (Petromyzon marinus) Predation: A Qualitative Analysis

1994 ◽  
Vol 51 (4) ◽  
pp. 942-945 ◽  
Author(s):  
A. L. Jensen
Keyword(s):  
Qualitative Analysis ◽  
Great Lakes ◽  
Lake Trout ◽  
Petromyzon Marinus ◽  
Sea Lamprey ◽  
Salvelinus Namaycush ◽  
Volterra Model ◽  
Model Parameters ◽  
Relative Importance ◽  
Simple Models

After invasion of the Great Lakes by the parasitic marine sea lamprey (Petromyzon marinus), lake trout (Salvelinus namaycush) populations crashed, but there remains some uncertainty concerning the relative importance of sea lamprey predation and harvesting in destruction of the fisheries. Some investigators believe overharvest was important; others think that the sea lamprey alone was enough. Simple models of predation assume monophagous predators and do not predict extinction of prey, but Larkin's modification of the Lotka–Volterra model results in extinction under some circumstances. The dynamics of sea lamprey predation on lake trout were investigated using Larkin's model, and crude estimates of the model parameters indicate that extinction is a likely outcome with or without a fishery.

Differential physiological response to sea lamprey parasitism between lake trout (Salvelinus namaycush) morphotypes from Lake Superior

2016 ◽  
Vol 73 (12) ◽  
pp. 1815-1829 ◽  
Author(s):  
Sara E. Smith ◽  
Shawn P. Sitar ◽  
Frederick W. Goetz ◽  
Mar Huertas ◽  
Brandon M. Armstrong ◽  
...  
Keyword(s):  
Life History ◽  
Protein Function ◽  
Lake Trout ◽  
Acute Stress ◽  
Lake Superior ◽  
Sea Lamprey ◽  
Salvelinus Namaycush ◽  
Weak Evidence ◽  
Reproductive Endocrine ◽  
Physiological Stressor

Assessment of stress from varied sources is usually evaluated using individuals derived from a single population and is assumed to represent all populations of that species. However, recent research has identified intraspecies variations in the stress response, which may be mediated by life history. We examined how life history can influence the physiological responses to an acute stress event by evaluating sea lamprey (Petromyzon marinus) parasitism response in two lake trout (Salvelinus namaycush) morphotypes: the lean and the siscowet. The morphotypes differ in that the lean grows faster, is more fecund, and has a shorter life span. In contrast, the siscowet grows slower, is older at maturity, and lives longer. Our study compared long-term parasitism responses between wild leans and siscowets in Lake Superior and immediate responses in laboratory parasitism trials using lake trout reared under common environmental conditions. Leans, but not siscowets, showed changes in steroid-binding protein function and weak evidence of gigantism in response to parasitism. Both morphotypes showed indications of reproductive endocrine alterations in response to parasitism. Our results demonstrate intraspecies variation in physiological stressor response, which is mediated by life history differences that could potentially have differential population implications.

Differences in Early Development Among Lake Trout (Salvelinus namaycush) Populations

1985 ◽  
Vol 42 (4) ◽  
pp. 737-743 ◽  
Author(s):  
William H. Horns
Keyword(s):  
Great Lakes ◽  
Lake Michigan ◽  
Lake Trout ◽  
Lake Superior ◽  
Relevant Information ◽  
Salvelinus Namaycush ◽  
The Other ◽  
Morphological Development ◽  
Green Lake ◽  
The Times

Genetic differences among surviving lake trout (Salvelinus namaycush) populations might be important for the reestablishment of self-sustaining populations in the Great Lakes, but little relevant information is available to guide stocking practices. I studied eggs and fry of four populations, two from Lake Superior, one from Trout Lake, and one (the Green Lake strain) derived in part from Lake Michigan. I found significant interpopulation differences in hatching and emergence times as well as in indices of morphological development rates. Interpopulation differences in morphological development at the times of emergence suggest that the Green Lake strain emerges at an earlier stage of morphological development than do the other populations. Between-lake differences are the most important sources of variability in my data; the Lake Superior populations were similar to one another, and variation among crosses within populations was small.

Changes in Biological Characteristics of the Sea Lamprey (Petromyzon marinus) as Related to Lamprey Abundance, Prey Abundance, and Sea Lamprey Control

1980 ◽  
Vol 37 (11) ◽  
pp. 1861-1871 ◽  
Author(s):  
John W. Heinrich ◽  
Jerry G. Weise ◽  
Bernard R. Smith
Keyword(s):  
Great Lakes ◽  
Chemical Control ◽  
Lake Trout ◽  
Lake Superior ◽  
Petromyzon Marinus ◽  
Control Program ◽  
Sea Lamprey ◽  
Biological Characteristics ◽  
Prey Abundance ◽  
Sea Lampreys

Biological characteristics of adult sea lampreys, Petromyzon marinus, in the Great Lakes changed in response to lamprey and prey abundance and the chemical control program. Sea lampreys collected as early as 1947, through 1978, from southern Lake Superior, northwestern Lake Michigan, the Ocqueoc River and Canadian shore of Lake Huron, and the Humber River of Lake Ontario were analyzed. Generally, abundance of sea lampreys peaked in each lake before the chemical control program began. The annual mean lengths and weights were relatively low when lampreys were abundant and increased as the numbers were reduced by the control efforts. As an indication of the change in sea lamprey weight per unit change in length, annual log10 weight on log10 length equations were solved at the arbitrary length of 410 mm. The values were plotted against years for each lake and interpreted with respect to chemical treatment periods. All slopes were negative before the control period and positive thereafter. Sea lamprey lengths and weights were low when fish stocks in the Great Lakes were near depletion. As salmonids again became abundant through stocking, lampreys grew larger. In Lake Superior, where detailed records on lake trout abundance have been available since 1959, a significant relation exists between the changes in the sea lamprey estimated weight values at 410 mm and in lake trout abundance (P < 0.01). Male sea lampreys were the dominant sex when populations of the parasite were high. A shift to a preponderance of females occurred as lamprey abundance declined.Key words: Petromyzon marinus, Salvelinus namaycush, abundance, sex ratio, weight–length relationship, chemical control

Movements of Hatchery-Reared Lake Trout in Lake Superior

1965 ◽  
Vol 22 (4) ◽  
pp. 999-1024 ◽  
Author(s):  
Richard L. Pycha ◽  
William R. Dryer ◽  
George R. King
Keyword(s):  
Great Lakes ◽  
Lake Trout ◽  
Lake Superior ◽  
Salvelinus Namaycush ◽  
Surface Currents ◽  
Gill Nets ◽  
East Lake ◽  
History Of ◽  
Keweenaw Peninsula

The history of stocking of lake trout (Salvelinus namaycush) in the Great Lakes is reviewed.The study of movements is based on capture of 24,275 fin-clipped lake trout taken in experimental gill nets and trawls and commercial gill nets.Yearling lake trout planted from shore dispersed to 15-fath (27-m) depths in [Formula: see text]. Most fish remained within 2 miles (3.2 km) of the planting site 2 months, but within 4 months some fish had moved as much as 17 miles (27 km). The highest abundance of planted lake trout was in areas 2–4 miles (3.2–6.4 km) from the planting site even 3 years after release. Distance moved and size of fish were not correlated.Dispersal of lake trout begins at planting and probably continues until the fish are mature. Most movement was eastward in southern Lake Superior and followed the counterclockwise surface currents. Movement is most rapid in areas of strong currents and slowest in areas of weak currents or eddies. Movement to areas west of the Keweenaw Peninsula was insignificant from plantings in Keweenaw Bay and nil from other plantings farther east. Lake trout planted in the eastern third of the lake dispersed more randomly than those planted farther west. Few fish moved farther offshore than the 50-fath (91-m) contour. Lake trout planted in Canadian waters made insignificant contributions to populations in US waters.

Lake Trout (Salvelinus namaycush) and Sea Lamprey (Petromyzon marinus) Populations in Lake Michigan, 1971–78

1980 ◽  
Vol 37 (11) ◽  
pp. 2047-2051 ◽  
Author(s):  
LaRue Wells
Keyword(s):  
Regression Model ◽  
Lake Michigan ◽  
Lake Trout ◽  
Lake Superior ◽  
Petromyzon Marinus ◽  
Sea Lamprey ◽  
Salvelinus Namaycush ◽  
Combined Effects ◽  
Widespread Application ◽  
Mortality Estimates

Lake trout (Salvelinus namaycush) was exterminated in Lake Michigan by the mid-1950s as a result of the combined effects of an intensive fishery and predation by the sea lamprey (Petromyzon marinus). The widespread application of lampricide in tributary streams had greatly reduced the abundance of lampreys by the early 1960s, and a program to restore self-sustaining populations of lake trout through stocking of yearlings and fingerlings was initiated in 1965. Although the hatchery-reared fish spawned widely in Lake Michigan each year after 1970, no progeny were observed except in an isolated area in Grand Traverse Bay. During 1971–78, sea lamprey abundance was generally greater in Wisconsin than in other parts of the lake. However, the rate of occurrence of sea lamprey wounds on lake trout dropped dramatically there in 1978 after the Peshtigo River, a tributary to Green Bay, was treated with lampricide. Application of Lake Michigan wounding rates to a regression model relating mortality to lamprey wounding developed from Lake Superior data, yielded lamprey-induced mortality estimates in 1977 of 5% in Michigan plus Indiana (combined) and 31% in Wisconsin; corresponding estimates for 1978 were 5 and 15%.Key words: lake trout, sea lamprey predation, abundance, Lake Michigan

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