Swartz Creek, MI, United States
Swartz Creek, MI, United States

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Goetz F.,University of Wisconsin - Milwaukee | Sitar S.,Marquette Fisheries Research Station | Jasonowicz A.,University of Washington | Seider M.,U.S. Fish and Wildlife Service
Transactions of the American Fisheries Society | Year: 2017

The reproductive biology of male and female lean, siscowet, redfin, and humper Lake Trout Salvelinus namaycush was assessed by measuring the gonadosomatic index (GSI) and by histological analysis of the gonads over 2 years from spring to fall at sites surrounding Isle Royale National Park, Lake Superior. Whole livers, otoliths, and ovaries were also collected to measure hepatosomatic index (HSI), age, and fecundity. In general, GSIs increased from spring to summer in male and female siscowets, leans, redfins, and humpers, and this was accompanied by a large increase in the number of vitellogenic (>2.0 mm) follicles in females. Postspawned ovaries and regressing testes were predominant in all morphotypes by October but were also observed in September, indicating that some spawning occurred at least by September. Further, preovulatory siscowet females (GSIs > 10) and siscowet males with fully mature and even regressing testes were observed in the spring and summer, indicating that spawning occurs at least in the spring and fall in siscowets at Isle Royale. For all morphotypes, average male HSIs were significantly lower than female HSIs. Absolute fecundity was positively related to size and age for all morphotypes. Humpers had the lowest absolute fecundity. Leans, redfins, and siscowets had similar fecundity relationships. The results conclusively demonstrate that deepwater siscowet Lake Trout reproduce at least during the spring and fall at Isle Royale and that leans, humpers, and redfins reproduce during the fall. In lakes that exhibit sympatric populations of deepwater and shallow-water ecotypes of Arctic Char Salvelinus alpinus, the deepwater form also spawns in both spring and fall. Our data and those on Arctic Char suggest that there is an adaptive strategy for maintaining alternative spawning times in the deepwater ecotypes in these populations. Received June 20, 2016; accepted November 2, 2016 Published online January 31, 2017 © American Fisheries Society 2017.


Goetz F.,University of Wisconsin - Milwaukee | Rosauer D.,University of Wisconsin - Milwaukee | Sitar S.,Marquette Fisheries Research Station | Goetz G.,University of Wisconsin - Milwaukee | And 6 more authors.
Molecular Ecology | Year: 2010

In Lake Superior there are three principal forms of lake trout (Salvelinus namaycush): lean, siscowet and humper. Wild lean and siscowet differ in the shape and relative size of the head, size of the fins, location and size of the eyes, caudal peduncle shape and lipid content of the musculature. To investigate the basis for these phenotypic differences, lean and siscowet lake trout, derived from gametes of wild populations in Lake Superior, were reared communally under identical environmental conditions for 2.5 years. Fish were analysed for growth, morphometry and lipid content, and differences in liver transcriptomics were investigated using Roche 454 GS-FLX pyrosequencing. The results demonstrate that key phenotypic differences between wild lean and siscowet lake trout such as condition factor, morphometry and lipid levels, persist in these two forms when reared in the laboratory under identical environmental conditions. This strongly suggests that these differences are genetic and not a result of environmental plasticity. Transcriptomic analysis involving the comparison of hepatic gene frequencies (RNAseq) and expression (quantitative reverse transcription-polymerase chain reaction (qPCR)) between the two lake trout forms, indicated two primary gene groups that were differentially expressed; those involving lipid synthesis, metabolism and transport (acyl- CoA desaturase, acyl-CoA binding protein, peroxisome proliferator-activated receptor gamma, and apolipoproteins), and those involved with immunity (complement component C3, proteasome, FK506 binding protein 5 and C1q proteins). The results demonstrate that RNA-seq can be used to identify differentially expressed genes; however, some discrepancies between RNA-seq analysis and qPCR indicate that methods for deep sequencing may need to be refined and/or different RNA-seq platforms utilized. © 2010 Blackwell Publishing Ltd.


Zorn T.G.,Marquette Fisheries Research Station | Wills T.C.,Lake St Clair Fisheries Research Station
North American Journal of Fisheries Management | Year: 2012

Excess sand bedload can significantly degrade salmonid habitat and populations. Successful use of sediment traps to restore habitat and salmonid populations on two Michigan streams in the early 1980s led to application of traps at well over 100 coldwater streams in Michigan and rivers throughout the USA within a decade. Unfortunately, little quantitative evaluation has occurred other than anecdotal observations for some traps. We conducted a broad-scale survey of 65 Michigan stream reaches with sediment traps by collecting data along transects upstream and downstream of the traps to assess downstream changes in substrate composition, channel depth, and channel stability in response to sediment traps. We found that recent applications of sediment traps (usually as stand-alone instream habitat treatments) had no significant effect on substrate, thalweg depth, or bank stability conditions in the reaches studied. Using reach-based estimates of specific stream power at the 10% annual exceedence flow, we identified areas where sediment traps could potentially destabilize channels. Specific stream power estimates were positively correlated with the preponderance of gravel and coarser substrate in stream reaches. Our study and previous assessments of sediment traps suggest that managers carefully consider their river and all potential management options when deciding if sediment traps will provide the best return on their investment. © American Fisheries Society 2012.


Madenjian C.P.,U.S. Geological Survey | Pothoven S.A.,National Oceanic and Atmospheric Administration | Schneeberger P.J.,Marquette Fisheries Research Station | Ebener M.P.,Chippewa Ottawa Resource Authority | And 3 more authors.
Journal of Great Lakes Research | Year: 2010

Dreissenid mussels have been regarded as a "dead end" in Great Lakes food webs because the degree of predation on dreissenid mussels, on a lakewide basis, is believed to be low. Waterfowl predation on dreissenid mussels in the Great Lakes has primarily been confined to bays, and therefore its effects on the dreissenid mussel population have been localized rather than operating on a lakewide level. Based on results from a previous study, annual consumption of dreissenid mussels by the round goby (Neogobius melanostomus) population in central Lake Erie averaged only 6 kilotonnes (kt; 1 kt = one thousand metric tons) during 1995-2002. In contrast, our coupling of lake whitefish (Coregonus clupeaformis) population models with a lake whitefish bioenergetics model revealed that lake whitefish populations in Lakes Michigan and Huron consumed 109 and 820 kt, respectively, of dreissenid mussels each year. Our results indicated that lake whitefish can be an important predator on dreissenid mussels in the Great Lakes, and that dreissenid mussels do not represent a "dead end" in Great Lakes food webs. The Lake Michigan dreissenid mussel population has been estimated to be growing more than three times faster than the Lake Huron dreissenid mussel population during the 2000s. One plausible explanation for the higher population growth rate in Lake Michigan would be the substantially higher predation rate by lake whitefish on dreissenid mussels in Lake Huron. © 2010.


Sitar S.P.,Marquette Fisheries Research Station | Jasonowicz A.J.,University of Wisconsin - Milwaukee | Jasonowicz A.J.,University of Washington | Murphy C.A.,Michigan State University | And 2 more authors.
Transactions of the American Fisheries Society | Year: 2014

We found that some lean (12.2%) and siscowet (58.0%) Lake Trout Salvelinus namaycush in populations in southern Lake Superior do not reproduce each year (i.e., display "skipped spawning") even though they have reached puberty. We measured skipped spawning in Lake Trout in southern Lake Superior and assessed its impact on reproduction by developing length-based and age-based ogives (i.e., probabilities of being mature). In populations in which skipped spawning is negligible, a maturity ogive can be considered equivalent to a reproduction ogive (probability of being reproductive). However, in populations in which skipped spawning is present, such as in lean and siscowet Lake Trout in southern Lake Superior, maturity and reproduction ogives are very different. We evaluated the influence of skipped spawning on a key stock assessment quantity-spawning stock biomass-by applying maturity and reproduction ogives to simulated populations. Furthermore, we evaluated whether skipped spawning was associated with lower energy reserves by testing for differences in the hepatosomatic index (HSI) according to maturity status. Our population simulations indicate that spawning stock biomass can be overestimated (8.3% for leans and 475% for siscowets) when skipped spawners are assumed to be a part of the spawning stock. An inflated reproductive potential of the population could allow for excessive fishing if quotas are based on these biased spawning stock biomass estimates. Siscowet Lake Trout that were skipping spawning had significantly lower energy reserves (assessed by HSI) than mature fish. The high incidence of skipped spawning in siscowets may be related to the reported slowed somatic growth, high population abundance, and low prey resources in southern Lake Superior, which supports the hypothesis that skipped spawning is a density-dependent response to limited energy resources. © American Fisheries Society 2014.


Zorn T.G.,Marquette Fisheries Research Station | Seelbach P.W.,Institute for Fisheries Research | Seelbach P.W.,U.S. Geological Survey | Rutherford E.S.,Institute for Fisheries Research | And 2 more authors.
Journal of the American Water Resources Association | Year: 2012

In response to concerns over increased use and potential diversion of Michigan's freshwater resources, and the resulting state legislative mandate, an advisory council created an integrated assessment model to determine the potential for water withdrawals to cause an adverse resource impact to fish assemblages in Michigan's streams. As part of this effort, we developed a model to predict how fish assemblages characteristic of different stream types would change in response to decreased stream base flows. We describe model development and use in this case study. The model uses habitat suitability information (i.e., catchment size, base-flow yield, and July mean water temperature) for over 40 fish species to predict assemblage structure in an individual river segment under a range of base-flow reductions. By synthesizing model runs for individual fish species at representative segments for each of Michigan's 11 ecological stream types, we developed curves describing how typical fish assemblages in each type respond to flow reduction. Each stream type-specific, fish response curve was used to identify streamflow reduction levels resulting in adverse resource impacts to characteristic fish populations, the regulatory standard. Used together with a statewide map of stream types, our model provided a spatially comprehensive framework for evaluating impacts of flow withdrawals on biotic communities across a diverse regional landscape. © 2012 American Water Resources Association.


Gorman O.T.,U.S. Geological Survey | Sitar S.P.,Marquette Fisheries Research Station
Transactions of the American Fisheries Society | Year: 2013

The fish community of Lake Superior has undergone a spectacular cycle of decline and recovery over the past 60 years. A combination of Sea Lamprey Petromyzon marinus depredation and commercial overfishing resulted in severe declines in Lake Trout Salvelinus namaycush, which served as the primary top predator of the community. Burbot Lota lota populations also declined as a result of Sea Lamprey depredation, largely owing to the loss of adult fish. After Sea Lamprey control measures were instituted in the early 1960s, Burbot populations rebounded rapidly but Lake Trout populations recovered more slowly and recovery was not fully evident until the mid-1980s. As Lake Trout populations recovered, Burbot populations began to decline, and predation on small Burbot was identified as the most likely cause. By 2000, Burbot densities had dropped below their nadir in the early 1960s and have continued to decline, with the densities of juveniles and small adults falling below that of large adults. Although Burbot populations are at record lows in Lake Superior, the density of large reproductive adults remains stable and a large reserve of adult Burbot is present in deep offshore waters. The combination of the Burbot's early maturation, long life span, and high fecundity provides the species with the resiliency to remain a viable member of the Lake Superior fish community into the foreseeable future. Received October 1, 2012; accepted July 9, 2013. © 2013 Copyright Taylor and Francis Group, LLC.


Zorn T.G.,Marquette Fisheries Research Station | Seelbach P.,U.S. Geological Survey | Wiley M.J.,University of Michigan
North American Journal of Fisheries Management | Year: 2011

We developed user-friendly fish habitat suitability tools (plots) for fishery managers in Michigan; these tools are based on driving habitat variables and fish population estimates for several hundred stream sites throughout the state. We generated contour plots to show patterns in fish biomass for over 60 common species (and for 120 species grouped at the family level) in relation to axes of catchment area and low-flow yield (90% exceedance flow divided by catchment area) and also in relation to axes ofmean and weekly range of July temperatures. The plots showed distinct patterns in fish habitat suitability at each level of biological organization studied and were useful for quantitatively comparing river sites. We demonstrate how these plots can be used to support stream management, and we provide examples pertaining to resource assessment, trout stocking, angling regulations, chemical reclamation of marginal trout streams, indicator species, instream flowprotection, and habitat restoration. These straightforward and effective tools are electronically available so that managers can easily access and incorporate them into decision protocols and presentations. © American Fisheries Society 2011.


Grossman G.D.,University of Georgia | Nuhfer A.,Hunt Creek Fisheries Research Station | Zorn T.,Marquette Fisheries Research Station | Sundin G.,University of Georgia | Alexander G.,Hunt Creek Fisheries Research Station
Freshwater Biology | Year: 2012

Fisheries models generally are based on the concept that strong density dependence exists in fish populations. Nonetheless, there are few examples of long-term density dependence in fish populations. Using an information theoretical approach (AIC) with regression analyses, we examined the explanatory power of density dependence, flow and water temperature on the per capita rate of change and growth (annual mean total length) for the whole population, adults, 1+ and young-of-the-year (YOY) brook trout (Salvelinus fontinalis) in Hunt Creek, Michigan, USA, between 1951 and 2001. This time series represents one of the longest quantitative population data sets for fishes. Our analysis included four data sets: (i) Pooled (1951-2001), (ii) Fished (1951-65), (iii) Unfished (1966-2001) and (iv) Temperature (1982-2001). Principle component analyses of winter flow data identified a gradient between years with high mean daily winter flows, high daily maximum and minimum flows and frequent high flow events, and years with an opposite set of flow characteristics. Flows were lower during the Fished Period than during the Unfished Period. Winter temperature analyses elucidated a gradient between warm mean, warm minimum and maximum daily stream temperatures and a high number of minimum daily temperatures >6.1°C, and years with the opposite characteristics. Summer temperature analyses contrasted years with warm summer stream temperatures vs years with cool summer stream temperatures. Both YOY and adult densities varied several-fold during the study. Regression analysis did not detect a significant linear or nonlinear stock-recruitment relationship. AIC analysis indicated that density dependence was present in 15 of 16 cases (four population segments×four data sets) for both per capita rate of increase (w i values 0.46-1.00) and growth data (w i values 0.28-0.99). The almost ubiquitous presence of density dependence in both population and growth data is concordant with results from other trout populations and other studies in Michigan. © 2012 Blackwell Publishing Ltd.


Zorn T.G.,Marquette Fisheries Research Station
North American Journal of Aquaculture | Year: 2015

Abstract: The effectiveness of stocking hatchery-reared Walleyes Sander vitreus to supplement native populations in large, open systems like the Great Lakes has not been thoroughly evaluated. I quantified recent contributions of stocked Walleye fingerlings to populations in Little Bay de Noc (LBDN) and Big Bay de Noc (BBDN) in northern Green Bay, Lake Michigan. Oxytetracycline-marked Walleye fingerlings were stocked in June, and late summer gill-net and night-time boat electrofishing surveys were used to index Walleye year-class abundance and collect juvenile Walleyes for hatchery mark evaluation. For the 2004–2009 year-classes, 76% of the age-0 to age-3 Walleyes examined from LBDN were of wild origin and 62% in BBDN were naturally reproduced fish. Survey catch rates of juvenile Walleyes were similar for stocked and nonstocked year-classes. Assessment catch rates of age-1 and age-2 Walleyes differed significantly by location, with average catch rates in LBDN often being ten times higher than those in BBDN. Age-0 Walleyes persisted to older ages and were well-represented at numerous sampling locations in LBDN, but few age-1 and older Walleyes were caught in BBDN. The differences in growth between hatchery-reared and wild Walleyes were minor compared with the differences between bays. Based on stocking records and creel estimates available since 1985, the harvest rate of Walleyes was not significantly correlated to the numbers of Walleyes stocked 4–6 years earlier in LBDN or BBDN. Despite low stocking rates, stocked fish likely provided some contribution (though not a statistically significant one) to Walleye year-classes and the sport fishery in LBDN, but their contribution in BBDN was less apparent. Managers should weigh the trade-offs of supplemental stocking in Great Lakes waters when considering requests for hatchery Walleyes in smaller lakes and rivers, especially when stocking resources are limited. Received February 20, 2014; accepted April 17, 2015 © 2015, © American Fisheries Society 2015.

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