A Model to Link Habitat Supply to Population Dynamics for Lake Trout (Salvelinus Namaycush) Populations in Western Lake Superior PDF Download

Author: John Netto (Ph. D.)
Publisher:
ISBN:
Category : Fish populations
Languages : en
Pages : 212

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Author: Cecilia Paola Ferrero
Publisher:
ISBN:
Category : Fish populations
Languages : en
Pages : 208

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Author: Elizabeth Stebbins
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 0

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Book Description
Correctly characterizing growth of fish within a population is a crucial component of fish biology and fishery management because, among other things, it informs population dynamics that affect management decisions. Size-at-age is a common metric of fish growth and is often measured at the population level with the assumption that, on average, all fish of a given age are a given size. Over time, several studies have shown that ignoring individual variability in growth can influence population parameter estimates and these inaccuracies can be propagated in population models that are used to calculate reference points for management. In the first chapter we develop a hierarchical, mixed-effects statistical growth model that measures individual variability in growth model parameters and partitions it into two sources. We fit this model to length-at-age data of lake trout (Salvelinus namaycush) from six populations in Lake Superior and show that individual-level variability exceeds population-level variability for this system, and persistent error contributes more to variability in length-at-age. In our second chapter, we simulate a population of fish and predict biological reference points, yield-per-recruit, and spawning stock biomass-per-recruit curves from the population using a 'standard' method that ignores individual variability and a 'true' method that accounts for size-selective mortality and its interaction with individual fish. We show that ignoring individual variability in these models results in overestimation of yield-per-recruit and the biological reference points F0.1 and FMAX. Further, spawning stock biomass-per-recruit is underestimated at low levels of fishing intensity and overestimated at high levels of fishing intensity when individual variability is ignored.

Author: B. A. Henderson
Publisher: Ontario, Ministry of Natural Resources, Fisheries Branch
ISBN:
Category : Fish populations
Languages : en
Pages : 26

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Author: Robert F. Raleigh
Publisher:
ISBN:
Category : Brook trout
Languages : en
Pages : 56

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Author: Christopher Todd Weeks
Publisher:
ISBN:
Category : Lake trout
Languages : en
Pages : 228

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Author: Matthew Michael Guzzo
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Aquatic ecosystems are expected to undergo major changes in response to climate change. Lake trout (Salvelinus namaycush) is predatory fish found in oligotrophic lakes of Canada and is considered a sentinel species for studying the impacts of warming on lakes due to its requirement for cold water. The objective of this thesis was to determine the impacts of warming on north-temperate lake trout populations. In Chapters 1-3, I used long-term datasets collected from small lakes near the southern extent of lake trout's distribution to determine how warming impacts thermal habitat and how these habitat changes cascade to alter the behaviour and growth of individuals and ultimately population-level characteristics of this species. I found that over a period when annual air temperatures increased by ≈ 2 ̊C there was a 14-day reduction, on average, in the ice-free season and an equal extension of summer - a period when littoral zone temperatures exceed the metabolic optimal for lake trout. Years with shorter springs and longer summers negatively impacts lake trout by limiting access to littoral prey, resulting in slower growth and reduced condition. I also found that the growth and size structure of an unexploited lake trout population shifted during this warming period; the population is now made up of a larger number of small individuals with lower condition and reduced life span. Lake trout also began to mature at younger ages and had reduced maximum size. Results suggest these changes in size-structure were not due to changes in the amount or size of prey fish or density-dependence, as the biomass of adult lake trout remained constant over time. In Chapter 4, I collected data from a northern lake to describe the seasonal ecology of this northern lake trout population and predict how warming might alter growth. I found that lake trout displayed similar seasonal cycles in habitat use and diet as in southern lakes, but that the use of littoral habitat was far reduced, likely due to the presence of pelagic prey fish and northern pike (Esox lucius) in this lake. Lastly, bioenergetic simulations indicated that the under a 2 ̊C warming scenario, the growth and consumption of lake trout would increase in this northern lake assuming prey was readily available.

Author: Jenni L. McDermid
Publisher:
ISBN: 9780494279519
Category :
Languages : en
Pages : 354

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Lake trout (Salvelinus namaycush) exhibit substantial life history variation across their range, but considerable local variation also occurs. Life history traits play a critical role in shaping population dynamics. As such, the observed life history variation makes it difficult to build conservation and management models. Populations should respond to varied environmental conditions by selecting the most favourable combination of life history traits. However, life history traits may alter as a result of phenotypic plasticity and/or genetic response to environmental conditions. This thesis examines the degree and mechanisms behind life history variation in lake trout. Variability is examined over the species range and within small geographic areas. Results indicate a strong association between enviromnental and lake trout life history variability. In particular, climate variables such as net thermal input and winter length and severity are correlated with a number of lake trout life history characteristics across the range. Lake morphology was associated with asymptotic sizes of lake trout, and shows contrasting associations with longevity and size at maturity in northern versus southern ranges. On a local scale, divergence in life history traits represented a combination of plastic responses and genetic adaptations to local conditions. The majority of life history traits examined in this thesis appeared to have a genetic basis; however stunted populations showed a plastic response to lack of forage fish. Yet, not all stunted populations within a region showed similar adaptive responses in early life history characteristics and we propose that the different responses may be predator mediated. Finally, the phenotypic divergence in life history traits among populations introduced from a common source approximately a century ago exhibited rapid plastic and genetic responses to novel environments. This thesis identifies that both plastic and genetic responses are common in lake trout, that these responses can occur quite rapidly, and that a significant number of environmental variables need to be considered before we can predict life history variation. These findings may be even more critical as populations continue to face stresses from climate change, overexploitation, habitat destruction, and introduced species.

Author: Lawrence Dean Jacobson
Publisher:
ISBN:
Category :
Languages : en
Pages : 438

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Author: Tyler R. Funnell
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 0

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Book Description
Rehabilitation of lake trout (Salvelinus namaycush), which historically was the coldwater apex predator of much of the Laurentian Great Lakes, is a priority for fishery management agencies in the region. In Lake Erie, the shallowest and southern-most Great Lake, successful rehabilitation of lake trout has been hindered by limited wild recruitment, possibly related to the lake's warm temperatures and restricted oxythermal habitat. I used acoustic telemetry tracking technology to investigate how lake trout spatial and thermal habitat use varies seasonally in Lake Erie to better understand whether limited recruitment could be caused by thermal conditions in the lake. As expected, lake trout were restricted to the offshore region of the eastern basin of Lake Erie during summer stratification. During fall, lake trout tended to occupy the southern nearshore region of the eastern basin, suggesting the importance of focusing spawning habitat restoration in this part of the lake. Tagged fish dispersed long distances at much higher frequencies than other Great Lakes populations of lake trout. Lake trout in Lake Erie occupied thermal habitat similar to other Great Lakes populations during summer stratification. Following destratification in fall, fish were exposed to warm temperatures, in some years for extended periods. Lake trout hatchery strains of Finger Lakes, NY, origin occupied similar summer temperatures and warm temperatures for more days during fall than Great Lakes origin strains, contrary to findings from Lakes Huron and Ontario. These results reveal behaviors that can inform management of lake trout in Lake Erie and throughout the Great Lakes and could begin to explain recruitment failure observed in Lake Erie.