Browsing by Subject "Fish"

Now showing 1 - 9 of 9
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    Defining stream integrity using biological indicators
    (2012-09) Dolph, Christine Laurie
    Biological indicators may offer the most comprehensive and accurate means to assess the integrity of streams and rivers, as changes in a biological community represent an integrated response to all environmental stressors present in an ecosystem. Biological indicators are typically designed to quantify and=or summarize important aspects of either ecosystem structure – the types and abundance of organisms found in a given habitat – or ecosystem function – rates and patterns of ecological processes such as primary and secondary production, nutrient cycling, and decomposition of organic matter. Increasingly, resource managers use such indicators to assess whether surface waters fulfill the requirements of their designated uses under the Clean Water Act. Despite the recognition that biological indicators can aid management decisions, critical questions remain regarding the best way to design, apply, and interpret them. In this dissertation, I used a suite of statistical and empirical approaches to evaluate the design and application of several different biological indicators of stream condition in various contexts and scales across Minnesota. Specifically, I used a bootstrap approach, together with a database of fish, macroinvertebrate, and environmental data collected by the Minnesota Pollution Control Agency (MPCA) between 1996 and 2006 from approximately 1500 stream sites across Minnesota, to quantify variability associated with an Index of Biological Integrity (IBI) developed by MPCA for fish communities in streams of two Minnesota river basins. I placed this variability into a management context by comparing it to impairment thresholds used in water quality determinations for Minnesota streams. I used the same MPCA dataset to develop predictive taxa richness models for fish and macroinvertebrates as additional indicators of the biological integrity of Minnesota streams, and evaluated these models for sensitivity and precision. I further determined whether fish and macroinvertebrate assemblages exhibited significant community concordance, and whether significantly concordant communities yielded equivalent indications of stream integrity at three nested spatial scales (statewide, ecoregion and catchment) in Minnesota. Finally, I used data from the MPCA database to evaluate relationships between selected environmental variables and the composition of fish and macroinvertebrate assemblages at all three spatial scales. I collected a second dataset of macroinvertebrate samples over the course of one year (2010) from three agricultural streams in southern Minnesota to evaluate relationships between structural and functional indicators of stream condition in response to a common stream conservation practice (i.e., reach-scale restoration). Specifically, I examined whether reach-scale restoration in disturbed agricultural streams in southern Minnesota was associated with changes in (1) macroinvertebrate taxa richness, (2) seasonal variability in macroinvertebrate community composition, and (3) secondary production (i.e., macroinvertebrate biomass over time). SUMMARY OF FINDINGS: 1. I found that 95% confidence intervals for IBIs scored on a 0-100 point scale ranged as high as 40 points. However, on average, 90% of IBI scores calculated from bootstrap replicate samples for a given stream site yielded the same impairment status as the original IBI score. I suggest that sampling variability in IBI scores is related to both the number of fish and the number of rare taxa in a field collection. A comparison of the effects of different scoring methods on IBI variability indicates that a continuous scoring method may reduce the amount of bias in IBI scores. 2. Predictive taxa-loss models for fish and macroinvertebrates both distinguished reference from non-reference sites. Predictive models for fish assemblages were less sensitive and precise than models for invertebrate assemblages, likely because of a relatively low number of common fish taxa. Significant concordance between fish and invertebrate communities occurred at the statewide scale as well as in six of seven ecoregions and 17 of 21 major catchments examined. However, concordance was not consistently indicative of significant relationships between rates of fish and invertebrate taxa loss at those same scales. Fish and invertebrate communities were largely associated with different environmental variables, although the composition of both communities was strongly correlated with stream size across all three scales. 3. I found no difference in macroinvertebrate taxa richness between restored and unrestored reaches of agricultural streams in southern Minnesota. However, both compositional similarity and secondary production were higher in restored reaches relative to unrestored reaches, suggesting that reach-scale restoration may have ecological effects beyond influences on diversity. These findings highlight the added complexity conveyed by a consideration of functional, as well as structural, indicators of stream condition. Higher productivity in the restored reaches was due largely to the disproportionate success of a small number of dominant taxa. Secondary production estimates were considerably lower than those reported for other similar-sized prairie streams; these low values may be indicative of stressful conditions for biotic life in the study streams.
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    Effects of Winter Hypoxia on Fish Communities in Northern Wisconsin
    (2023-07) Ellman, Mark
    Hypoxia is a significant source of winter mortality for freshwater fish in north-temperate lakes and has the potential to alter fish communities. A multi-year dataset on Buckskin Lake, a shallow, productive drainage lake in northern Wisconsin with a history of winterkill, allowed the investigation of the effects of periodic winter hypoxia on fish communities. An aeration system was installed in 1984, which raised winter oxygen levels to levels sufficient for higher fish survival. In the winter of 2007-2008, the aerator system failed, causing an extensive winterkill. The lake was sampled from 2002-2005, before the aerator failure, and in 2008-2009, after the winterkill event. In addition, 16 similar lakes in the area with no winterkill history were sampled using similar methods. Using the combined datasets, two hypotheses were tested with non-metric multidimensional scaling (NMDS) and PERMANOVA analyses. We hypothesized that (1): after 18 years of aeration, the Buckskin Lake fish community from 2002-2005 would be similar to the non-winterkill lakes due to the recolonization of species from connected lakes, and (2): the fish community changed significantly in the lake due to the 2007-2008 winterkill event. The first hypothesis was not supported, as NMDS and PERMANOVA analyses showed that Buckskin Lake retained a fish community distinct from the non-winterkill lakes. Our findings were consistent with the second hypothesis: an incomplete winterkill occurred in 2007-2008 due to lack of aeration, causing changes in fish abundances, including the reduction of game fish species and centrarchids, with no notable extinctions. Together, our findings indicate that winter aeration may improve gamefish survival and allow lakes with winterkill tendency to support sport fish communities with healthy piscivore populations such as walleye and largemouth bass, which would be otherwise greatly reduced.
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    Examining genetic diversity, outbreeding depression, and local adaptation in a native fish local adaptation in a native fish reintroduction program.
    (2010-05) Huff, David Derland
    Reintroductions are a common approach for preserving intraspecific biodiversity in fragmented landscapes; however, reintroduced populations are often smaller and more geographically isolated than native populations. Reintroductions may therefore exacerbate the reduction in genetic variability initially caused by population fragmentation due to the small effective population size of the reintroduced populations. Mixing genetically divergent sources is assumed to alleviate this issue by increasing genetic diversity, but the effects on genetic diversity are often not monitored and there are potential negative tradeoffs for mixing genetically distinct sources. I examined the consequences of mixed-source reintroductions on the ancestral composition, genetic variation and fitness of a small stream fish, the slimy sculpin (Cottus cognatus), from three source populations at nine reintroduction sites in southeast Minnesota. I used microsatellite markers to evaluate allelic richness and heterozygosity in the reintroduced populations relative to computer simulated expectations. I then inferred the fitness of each crosstype in the reintroduced populations by comparing their overall persistence, growth rates, and relative body conditions. Finally, I modeled the response of fitness related variables in the reintroduced populations to variation in habitat using a combination of regression and ordination methods. Ancestry analysis revealed that one of the three sources had more ancestors than the other two sources at most reintroduction sites. Sculpins in reintroduced populations exhibited higher levels of heterozygosity and allelic richness than the sources, but only slightly higher than the most genetically diverse source population. Simulations of maximum genetic variation indicated only a modest expected increase over the most diverse source. Growth rate, body size, and relative body condition suggest significantly reduced fitness in second generation hybrids. I detected evidence of local adaptation in the source populations based on greater predicted fitness for each source in its respective habitat. This local adaptation is strongly associated with a gradient in winter water temperatures. My study indicates that using more than one source for reintroductions may not substantially enhance genetic diversity. Furthermore, using multiple sources risks disruption of important adaptations and may cause outbreeding depression. Future reintroductions may be improved by evaluating the potential for local adaptation in ongoing reintroduction programs.
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    Improved diagnosis and management of viral hemorrhagic septicemia virus in fish
    (2013-02) Phelps, Nicholas B. D.
    Viral hemorrhagic septicemia virus (VHSV) is a highly contagious and pathogenic virus, affecting more than 70 farm raised and wild fish species worldwide. A new viral strain (VHSV-IVb) has proven both virulent and persistent, spreading throughout the Great Lakes of North America and to inland water bodies in the region. As this new biological hazard continues to grow, so too must our understanding of the disease. The focus of this dissertation is to improve diagnostic capacity and management of VHSV-IVb to rapidly respond to outbreaks, prevent further dissemination, and scientifically justify current prevention strategies. To better understand the geographic distribution of the virus, we used a modified real time reverse transcription-polymerase chain reaction (rRT-PCR) assay for high-throughput testing of fish for VHSV. The assay was shown to be twice as sensitive as the gold standard, virus isolation, and did not cross react with other viruses found in fish. In addition, the diagnostic turnaround time was reduced from 28-30 days for virus isolation to 2-4 days for rRT-PCR. To demonstrate the usefulness of the rRT-PCR assay, 115 high priority water bodies in Minnesota were tested by both methods from April 2010 - June 2011. All survey sites tested negative for VHSV by both methods. The survey results have informed fisheries managers on the absence of VHSV in Minnesota and have better prepared them for the eventual arrival of the disease. In addition, the results demonstrate the value of this rRT-PCR as a surveillance tool to rapidly identify an outbreak so that it can be controlled in a timely manner. The aforementioned rRT-PCR assay (Phelps et al. 2012) along with another (Jonstrup et al. 2012), were evaluated for the potential for sample-induced inhibition from common diagnostic samples, including kidney/spleen, entire viscera, and ovarian fluid. The detection of high, medium, and low VHSV-IVb dilutions in each tissue type was not affected using the assay by Jonstrup et al (2012). However, using the assay by Phelps et al. (2012), the detection of VHSV-IVb was decreased for the kidney/spleen samples spiked with low virus levels and increased for the ovarian fluid spiked with medium virus levels. Entire viscera, the tissue type most likely to inhibit the rRT-PCR reaction, did not affect the sensitivity of virus detection for either assay. The emergence of VHSV-IVb in the Great Lakes region has resulted in unprecedented regulatory response to better manage the disease. In Minnesota, all VHSV-susceptible fish must be inspected annually prior to intra or interstate movement - a significant bottleneck for the aquaculture industry. In 2009, Minnesota enacted legislation requiring fish for regulatory health inspections to be collected by a Minnesota Department of Natural Resources (MNDNR) approved individual. The so-called Fish Health Collector could be 1) an American Fisheries Society - Fish Health Section Fish Health Inspector or Pathologist, 2) an accredited veterinarian with approved training, or 3) an individual (i.e. MNDNR field biologist) with approved training. In response, a fish health collector training workshop was developed for veterinarians and field biologists to fulfill the MNDNR requirements. A manual was developed to supplement a full-day workshop and provide the basic information and references to perform a fish health collection. This training resulted in a sufficient number of fish health collectors, well distributed across Minnesota, now available to rapidly respond to a disease outbreak and better serve the regulatory needs of the aquaculture industry. In the USA, current state and federal fish health regulations target the spread of VHSV-IVb through movement restrictions of live fish but largely ignore the potential for the virus to be spread through the commercial distribution and use of frozen baitfish from VHSV-IVb positive regions. Some state laws do require treatment of frozen baitfish to inactivate VHSV and additional methods have been proposed, but there have been few scientific studies examining the efficacy of these treatments. In an effort to evaluate these treatments, bluegills were challenged with VHSV-IVb, frozen to represent standard industry methods, disinfected by various treatments, and tested for infectious VHSV-IVb using virus isolation. The virus was isolated from 70% of fish subjected to three freeze thaw cycles. All other treatment methods were effective in inactivating the virus, including treatment with isopropyl alcohol, mineral oil, salt with borax, and dehydration. Dehydration followed by rehydration is rapid and effective, and therefore, seems to be the best option for inactivating VHSV-IVb present in frozen baitfish while maintaining their usefulness as bait. Monitoring or regulating all risk factors for the transmission of VHSV is an infeasible task. A semi-quantitative risk assessment model was utilized to focus VHSV management efforts in Minnesota. The risk of VHSV introduction to major watersheds in Minnesota was directly correlated with proximity to Lake Superior, the only VHSV-positive waterbody in the state. Although the current regulations are uniform across Minnesota, the risk varied for specific locations within the watersheds. For example, the introduction of game fish for stock enhancement (a common fisheries management practice) was found to be a significant risk factor for VHSV introduction into public waterbodies and waterbodies frequently used for wild baitfish harvest. Aquaculture facilities with strict biosecurity programs and frequent health inspections received the lowest risk scores and were largely considered protected and of low risk for VHSV introduction. These results suggest the current management strategy, based on political boundaries, should be reevaluated. A risk-based management strategy would better allocate efforts to watersheds or specific waterbodies at higher risk and relax efforts in areas of lower risk of VHSV introduction in Minnesota.
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    An Integrated Approach to Assessing Multiple Stressors for Coastal Lake Superior
    (2011) Niemi, Gerald J; Reavie, Euan; Peterson, Gregory S; Kelly, John R; Johnston, Carol A; Johnson, Lucinda B; Howe, Robert W; Host, George; Hollenhorst, Thomas; Danz, Nick; Ciborowski, Jan H; Brown, Terry; Brady, Valerie; Axler, Richard P
    This peer-reviewed article summarizes research conducted under the Great Lakes Environmental Indicators (GLEI) project initiated by the authors in 2001. The authors assessed the status of Lake Superior’s coastal ecosystem relative to over 200 environmental variables collected from GIS data sets for the enture US Great Lakes basin. These were assessed using gradients including atmosphereic deposition, agriculture, human population and development, land cover, point source pollution, soils and a cumulative stress index. Relationships of biological assemblages of birds, diatoms, fish and invertebrates, wetland plants, soils and stable isotopes to these gradients were then assessed. Key findings are extracted and reproduced below. Biological indicators can be used both to estimate ecological condition and to suggest plausible causes of ecosystem degradation across the U.S. Great Lakes coastal region. Here we use data on breeding bird, diatom, fish, invertebrate, and wetland plant communities to develop robust indicators of ecological condition of the U.S. Lake Superior coastal zone. Sites were selected as part of a larger, stratified random design for the entire U.S. Great Lakes coastal region, covering gradients of anthropogenic stress defined by over 200 stressor variables (e.g. agriculture, altered land cover, human populations, and point source pollution). A total of 89 locations in Lake Superior were sampled between 2001 and 2004 including 31 sites for stable isotope analysis of benthic macroinvertebrates, 62 sites for birds, 35 for diatoms, 32 for fish and macroinvertebrates, and 26 for wetland vegetation. A relationship between watershed disturbance metrics and 15N levels in coastal macroinvertebrates confirmed that watershed-based stressor gradients are expressed across Lake Superior’s coastal ecosystems, increasing confidence in ascribing causes of biological responses to some landscape activities. Several landscape metrics in particular—agriculture, urbanization, human population density, and road density—strongly influenced the responses of indicator species assemblages. Conditions were generally good in Lake Superior, but in some areas watershed stressors produced degraded conditions that were similar to those in the southern and eastern U.S. Great Lakes. The following indicators were developed based on biotic responses to stress in Lake Superior in the context of all the Great Lakes: (1) an index of ecological condition for breeding bird communities, (2) diatom-based nutrient and solids indicators, (3) fish and macroinvertebrate indicators for coastal wetlands, and (4) a non-metric multidimensional scaling for wetland plants corresponding to a cumulative stress index. These biotic measures serve as useful indicators of the ecological condition of the Lake Superior coast; collectively, they provide a baseline assessment of selected biological conditions for the U.S. Lake Superior coastal region and prescribe a means to detect change over time.” Key points: “In general, the U.S. Great Lakes coastal region of Lake Superior shows greater overall stress in the southern regions compared with relatively low overall stress in the northern regions. These patterns are primarily due to agricultural land use, higher human population densities, and point sources in the eastern and western portions on the south shore, while the north shore at the western end of Lake Superior is primarily forested with relatively sparse human population densities. Coastal regions of Lake Superior can be found at each of the extremes of the disturbance gradients. This includes relatively pristine watersheds in the northern regions with low human population densities and little agriculture that contrast with regions of relatively high populations with industrial activity such as Duluth-Superior in Minnesota-Wisconsin and Sault Ste. Marie Michigan at the other end of the gradient. The U.S. Lake Superior coastal region varies widely in the degree of human-related stress; generally, levels of stress decrease from south to north but with considerable variation, especially along the southern shore due to local agricultural activity and the presence of several population and industrial centers. In spite of a lack of latitudinal variation, there is human-induced, watershed scale variability across the Lake Superior coast. Compared to the other Great Lakes, Lake Superior coastal fish communities had more generally intolerant fish and more turbidity intolerant fish. Coastal fish community composition reflected the higher levels of suspended solids associated with human alteration to watersheds. The most disturbed sites on Lake Superior had greater proportions of non-native species and fewer bottom-feeding taxa.
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    Pathway-based approaches in ecotoxicological research: Evaluation of complex mixtures on fathead minnow reproduction and development
    (2015-07) Cavallin, Jenna
    Mixtures of natural and synthetic compounds are ubiquitously detected in wastewater treatment plant (WWTP) effluents and surrounding surface waters. Of particular concern are endocrine-disrupting compounds that can affect hypothalamic-pituitary-gonadal axis function in exposed organisms. Reproductive effects of exposure to a historically estrogenic WWTP effluent were examined in a 21-d real-time exposure using fathead minnows. Molecular and biochemical endpoints representing key events along adverse outcome pathways linking estrogen receptor activation and other molecular initiating events to reproductive impairment were examined. Analytical chemistry results were used to construct a chemical-gene interaction network to aid in targeted gene expression analyses. Estrone was consistently detected in the effluent and was subsequently used in an exposure aimed to implement whole-mount in situ hybridization with fathead minnow embryos to examine developmental effects at early-life stages. The results provide insights into the significance of pathway-based effects with regard to predicting adverse reproductive and developmental outcomes.
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    Riparian Forest Buffers for Trout Habitat Improvement
    (2010-06-30) Bongard, Phyllis; Wyatt, Gary; Nerbonne, Brian
    Creating an educational program that promotes the benefits of riparian forest buffers. The approach includes developing educational materials based on a literature review and establishing a demonstration on an existing DNR-designated trout stream, the Vermillion River in Dakota County.
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    Spatial and temporal variability in zooplankton-fish interactions in freshwater communities.
    (2011-06) Holbrook, Beth Victoria
    Abiotic and biotic factors interact at multiple scales to create heterogeneity in the distribution of zooplankton and zooplanktivorous fish in the pelagic area of freshwater lakes. In this dissertation, I explored the predator-prey relationship between these trophic levels in four studies conducted at a variety of spatial and temporal scales. The objective was to identify the processes that may structure spatial heterogeneity in these populations. At the smallest scales in the laboratory, I simulated light and temperature conditions similar to those found in an oligotrophic lake and observed interactions between age-0 lake trout (Salvelinus namaycush) and mysids (Mysis diluviana), and determined that the intake rate of age-0 lake trout (mg min-1) could be modeled as a function of mysid biomass (mg m-2). I then applied this model to field data collected at intermediate scales at a spawning shoal in Lake Superior and determined that age-0 lake trout distributed in a spatially predictable pattern based on maximizing their growth rate potential. I also explored the more general relationship between pelagic zooplankton biomass and fish density at intermediate spatial scales in three north temperate lakes. In all six depth strata that I analyzed, there was consistent and significant autocorrelation in the distribution of zooplankton biomass, but spatial structure in the distribution of fish density was weaker and more variable. I also detected a significant bottom-up influence of zooplankton biomass on the spatial structure of fish density in three of the six depth strata that I analyzed, but I did not detect any top-down influences of fish density on the spatial structure of zooplankton biomass. Finally, I explored the influence of surface temperature and mesoscale eddies on the distribution of epilimnetic zooplankton biomass and fish density at large scales in Lake Superior. Circulation patterns associated with prevailing wind conditions could explain some of the spatial patterns in zooplankton biomass, but epilimnetic fish distributions showed no pattern during both years of the study.
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    Volumetric velocity measurement of aquatic predator-prey interactions
    (2013-12) Adhikari, Deepak
    The aim of this study is to develop a novel multi-scale volumetric measurement system and flow facility, and apply it to improve understanding of aquatic predator-prey interactions. A combined infrared tomographic PIV + 3D PTV system was developed and demonstrated. Tomographic PIV was used to obtain the volumetric velocity field of the flow, while the 3D PTV was used to track the prey, and the eye of the predator, in the same volume. A visual hull technique was implemented to mask out the objects (such as fish) appearing within the reconstructed tomographic PIV volumes, ensuring that velocity vectors near the object/fish were not contaminated during PIV cross-correlation. Copepods, which make up the majority of the oceanic zooplanktons, are known to sense flow disturbed by approaching predators and can execute sudden high-speed swim (or jump) to escape predation. Although their response to local flow disturbances has been studied, their sensing and swimming response to live predators (fish) is not well understood. Three series of experiments were implemented - (1): Copepod interactions with a wall-mounted cylinder in cross-flow; (2): Predator-prey interactions in still water; (3): Predator-prey interactions in unsteady/turbulent flow. From the experiments, copepods appeared to respond (jump) to a large and sudden increase in local maximum principal strain rate (MPSR) of the fluid, instead of a fixed threshold quantity. For fish predation in still water, zebrafish were first observed to approach slowly, followed by sudden acceleration (ram feeding) to feed on copepods. Using a potential flow model, it was found that this strategy might not be sufficient to capture copepods successfully. Thus, zebrafish were found to execute suction feeding simultaneously to increase chances of predation success. In uniform cross flow, a coral reef fish (blenny) used a similar slow approach - ram feeding strategy to feed on copepods, but it rarely captured them. However, turbulent cross flow increased the chances of predation by allowing the fish to approach closer to a copepod, and preventing the copepod from detecting hydrodynamic signals from the approaching predator.