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Saint Paul, MN, United States

Sietman B.E.,00 Lafayette Road | Davis J.M.,801 South Oak Street | Hove M.C.,University of Minnesota
American Malacological Bulletin | Year: 2012

Diverse strategies have evolved in freshwater mussels to promote the transfer of their parasitic larvae to host fish. Among these, modification of the mantle as a host attracting lure has been well-documented in the Tribe Lampsilini, but only recently reported in the Tribe Quadrulini. Here we describe mantle modifications and glochidia release behaviors in five quadruline species, including members of the Quadrula quadrula (Rafinesque, 1820), Q. pustulosa (Lea, 1831), and Q. metanevra (Rafinesque, 1820) species groups. Displays were motionless and consisted of inflated mantle tissue surrounding the excurrent aperture. Gross display morphology was largely variable among species: Q. fragosa (Conrad, 1835) and Tritogonia verrucosa (Rafinesque, 1820) had relatively large, uniquely shaped displays; Cyclonaias tuberculata (Rafinesque, 1820) and Q. pustulosa had smaller, stomate-shaped displays; and Q. metanevra had a diminutive, polyp-like display. Cyclonaias tuberculata exhibited a bimodal host infection strategy where individuals had either a mantle display or released a gelatinous conglutinate. Quadrula pustulosa and Q. metanevra expelled glochidia in a forceful burst when their displays were touched. Quadruline mantle displays do not clearly mimic identifiable aquatic organisms suggesting they may represent non-specific food items to their fish hosts. Source


Fieberg J.,Biometrics Unit | Cornicelli L.,00 Lafayette Road | Cornicelli L.,University of Minnesota | Fulton D.C.,University of Minnesota | Grund M.D.,Farmland Research Unit
Journal of Wildlife Management | Year: 2010

We used a simple yet powerful method for judging public support for management actions from randomized surveys. We asked respondents to rank choices (representing management regulations under consideration) according to their preference, and we then used discrete choice models to estimate probability of choosing among options (conditional on the set of options presented to respondents). Because choices may share similar unmodeled characteristics, the multinomial logit model, commonly applied to discrete choice data, may not be appropriate. We introduced the nested logit model, which offers a simple approach for incorporating correlation among choices. This forced choice survey approach provides a useful method of gathering public input; it is relatively easy to apply in practice, and the data are likely to be more informative than asking constituents to rate attractiveness of each option separately. © The Wildlife Society. Source


Ahrenstorff T.D.,University of Minnesota | Hrabik T.R.,University of Minnesota | Pereira D.L.,00 Lafayette Road
Oecologia | Year: 2013

The movement patterns and body size of fishes are influenced by a host of physical and biological conditions, including temperature and oxygen, prey densities and foraging potential, growth optimization, and predation risk. Our objectives were to (1) investigate variability in vertical movement patterns of cisco (Coregonus artedi) in a variety of inland lakes using hydroacoustics, (2) explore the causal mechanisms influencing movements through the use of temperature/oxygen, foraging, growth, and predation risk models, and (3) examine factors that may contribute to variations in cisco body size by considering all available information. Our results show that cisco vertical movements vary substantially, with different populations performing normal diel vertical migrations (DVM), no DVM, and reverse DVM in lakes throughout Minnesota and northern Wisconsin, USA. Cisco populations with the smallest body size were found in lakes with lower zooplankton densities. These smaller fish showed movements to areas of highest foraging or growth potential during the day and night, despite moving out of preferred temperature and oxygen conditions and into areas of highest predation risk. In lakes with higher zooplankton densities, cisco grew larger and had movements more consistent with behavioral thermoregulation and predator avoidance, while remaining in areas with less than maximum foraging and growth potential. Furthermore, the composition of potential prey items present in each lake was also important. Cisco that performed reverse DVM consumed mostly copepods and cladocerans, while cisco that exhibited normal DVM or no migration consumed proportionally more macro-zooplankton species. Overall, our results show previously undocumented variation in migration patterns of a fish species, the mechanisms underlying those movements, and the potential impact on their growth potential. © 2013 Springer-Verlag Berlin Heidelberg. Source


Holdsworth A.R.,00 Lafayette Road | Holdsworth A.R.,University of Minnesota | Frelich L.E.,University of Minnesota | Reich P.B.,University of Minnesota | Reich P.B.,University of Western Sydney
Ecosystems | Year: 2012

Earthworm invasion in North American temperate forest reduces forest floor mass, yet the interactions between litter composition, invasive earthworm community composition, and forest floor structure and composition are not well understood. For 2 years, we compared disappearance of leaf litter in field mesocosms in which we manipulated litter composition (monocultures of Quercus rubra, Acer saccharum, and Tilia americana litter, and an equal mixture of all three) and thereby the initial litter chemistry (C, C fractions, N, Ca) in sites with and without the major litter-feeding invasive earthworm species. The disappearance of litter mass followed the same ranking at both the sites: T. americana > equal mixtures > A. saccharum ≥ Q. rubra. However, differences in disappearance rate between the sites depended on litter composition and time. The differences in mass loss among litters of different compositions were greatest at the site invaded by the large litter-feeding earthworm, Lumbricus terrestris, and especially for T. americana and the mixture. Similarly, observed disappearance of the litter mixture was faster than predicted by an additive model at the site with L. terrestris, especially for the higher quality litter component in early summer. Initial litter calcium content was the best predictor (R 2 ≥ 0. 90) of overall litter mass remaining each year, supporting the idea of the importance of calcium in forest floor dynamics, especially in the presence of calciferous, invasive earthworms. © 2012 Springer Science+Business Media, LLC. Source


Pierce R.B.,1201 East Highway 2 | Tomcko C.M.,1201 East Highway 2 | Pereira D.L.,00 Lafayette Road | Staples D.F.,00 Lafayette Road
Transactions of the American Fisheries Society | Year: 2010

Understanding factors that affect catchability is important for interpreting fish catches from research index netting and comparing fish populations from different habitats. Population density estimates and gill-net catch rates were compared for age-2 and older northern pike Esox lucius in 16 north-central Minnesota lakes that varied in physical characteristics and northern pike populations. When northern pike density was calculated using total surface area of the lakes, numerous factors appeared to influence gill-net catchability. Those factors included several lake basin shape metrics, northern pike size structure, and northern pike density, with density dependence in catchability being especially problematic for interpreting gill-net catches. The critical finding in this study was that calculating density using littoral area rather than total surface area caused evidence of density-dependent catchability and all other relationships with catchability to completely disappear. Catchability became independent of northern pike density and lake basin shape metrics when density was calculated using littoral area. Correlations with density (calculated from total surface area) and other factors were simply artifacts of underlying interrelationships between the morphology of lake basins, northern pike population characteristics, and density-dependent processes. Catchability estimates for littoral habitat averaged 0.20 ha/net and ranged from 0.09 to 0.43 ha/net among the lakes. Although the relationship between gill-net catch and population density indicated that gillnetting could be a useful tool for comparing northern pike populations from different lakes, a predictive model fitted to the observed gill-net catch rates and population densities from 16 lakes had low precision. Results from this study illustrate the importance of a comprehensive understanding of fish ecology, including spatial habitat use, when interpreting survey results. © Copyright by the American Fisheries Society 2010. Source

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