The Feeding Mechanics of the Gizzard Shad (Dorosoma Cepedianum)

This thesis was submitted to the Department of Systematics and Ecology and the Faculty of the Graduate School of the University of Kansas in partial fulfillment of the requirements for the degree of Doctor of Philosophy.Field studies have shown that young gizzard shad (Dorosoma eepedianum) are carnivores, visually feeding on individual zooplankton. Shad larger than 30 .mm are omnivores, feeding predominantly as filter-feeders on both phytoplankton and zooplankton. This study experimentally identified and quantified the causal mechanisms determining the feeding selectivity and feeding rate of filter-feeding gizzard shad. Laboratory observations found shad to filter-feed by inhaling water and food through expansion of the buccal and opercular cavities. Shad did not visually select and attack individual zooplankter prey items, but swam through the water inhaling water containing prey with a rapid series of undirected suctions. Shad filtering rate, the volume of water inhaled per minute, was equal to the multiple of the volume of the expanded buccal cavity and the pumping rate. I determined buccal volume by making plaster of Paris molds of the expanded buccal cavity. The volume of the expanded buccal cavity increased as a power function of shad length. Pumping rate, measured by high speed movie films and visual observation, decreased with shad length. Filtering rate increased as a power function of shad length with shad 17 cm in standard length filtering over one liter of water per minute. The actual rate that particles were inhaled and ingested was determined.by the shad's capture efficiency and filtering efficiency. Capture efficiency is a function of both the shad's capture and the prey's escape mechanisms. A shad's suction pump mechanism creates a flow into the mouth similar to flow into a pipe. I simulated a fishlike suction intake using a siphon system which afforded control over the three variables of fish suction intakes; mouth opening size, buccal volume, and buccal expansion rate. The simulated suction inhaled 10 ml into a tube 1.0 cm in diameter in 0.4 sec. The capture probability of the. simulated suction for zooplankter prey was highest for the cladocerans Ceriodaphnia reticulata (P = •96), Daphnia galeata mendotae (P = .92), and Daphnia pulex (P = .76); intermediate for cyclopoid copepods (mostly Cyclops sp. and Mesocyclops sp.) (P = .28) and Cyclops scutifer (P = .24); and lowest for the calanoid copepod Diaptomus pallidus (P = .07). To test the results of the capture experiments, the relative feeding rates of gizzard shad on a mixture of different zooplankton were determined in laboratory experiments and compared to predictions based on the capture probabilities. Shad feeding rate constants, k (liters/hr), were lowest on Diaptomus spp. (xk = .67), intermediate on cyclopoid copepods (xk = 1.37) and highest on D. galeata mendotae (xk = 3.60), C. reticulata (xk = 3.00) and copepod nauplii (xk = 4.01). These experiments show that differential capture probabilities of nonvisual-feeding planktivores result in an apparent feeding selectivity for zooplankton which have poor escape ability. Particles inhaled into the mouth are filtered from the water by the gill rakers. The shad's filtering efficiency was determined by measuring the interraker spaces. Cumulative frequencies of interraker distances weighted for raker length show that filtering efficiency for particles 1 to 70 microns was a hyperbolic function of particle size with particles 7 0 microns or larger filtered with 100% efficiency. This filtering efficiency would result in an apparent feeding selectivity for large algae versus small algae. The feeding rate of filter-feeding gizzard shad on a particular prey type was equal to the multiple of 4 factors: (1) prey density, (2) shad filtering rate, (3) shad capture efficiency, and (4) shad filtering efficiency. This feeding rate model was confirmed in an experiment which compared computer simulated to observed shad feeding rates

Estimation of the Groundwater Nutrient Input to Clear Lake

A “Diagnostic and Feasibility Study” of Clear Lake, funded primarily by the IDNR, the City of Clear Lake, Cerro Gordo County, Hancock County, the Hancock and Cerro Gordo County offices of the NRCS, and Iowa State University (cost-share) was completed in 2001. The purpose of this two-year project was to study the Clear Lake watershed and community, to determine water-quality problems and their causes, and to suggest potential remedial measures. The feasibility of remedial alternatives is still under review by the IDNR and the City of Clear Lake

Freshwater Community Responses to Mixtures of Agricultural Pesticides: Synergistic Effects of Atrazine and Bifenthrin

This study was an investigation of the effects of the herbicide atrazine and the insecticide bifenthrin on lake communities. The study was conducted in two phases: in phase one, we examined the effects of environmentally realistic levels of atrazine and bifenthrin, based on published data of concentrations measured in fresh waters; in phase two, the impacts of higher levels of atrazine and bifenthrin were investigated, based on concentrations used in previous studies. The factorial designed experiment included three levels of bifenthrin (0, 1/39, and 1/287 ngL in phase one and 0, 1/125, and 1/3150 ngL in phase two) cross-classified with three levels of atrazine (0, 1/15, and 1/153 ugL in phase one and 0, 1/385, and 1/2167 ugL in phase two), with duplicate replication of each treatment combination. Pesticides were added to 5,500 L fiberglass tanks containing natural plankton assemblages and bluegill. Tanks were sampled 7 and 14 d following the first pesticide treatment and 7 d after the second pesticide addition. In phase one of the study, atrazine significantly reduced chlorophyll concentrations and turbidity on day 7 Wand had no significant impact on primary productivity or algal cell densities. Atrazine also had a significant negative effect on copepod nauplii and rotifers (days 7 and 14) and on Bosmina and particulate phosphorus in the 20-200 um size fraction (day 14). Bifenthrin significantly reduced Bosmina (days 7 and 14), cyclopoid copepodids (days 7 and 14), and copepod nauplii (day 14), however bifenthrin increased rotifers at day 7. Bifenthrin addition also increased colonial green algae and decreased particulate phosphorus in the 20-200 um size fraction on day 7 and decreased turbidity and particulate phosphorus in the >200 um size fraction on days 7 and 14. Only one fish mortality (in the high bifenthrin, no atrazine treatment combination) occurred during phase one of the study. Significant interaction effects were found only for Bosmina (day 14), rotifers (day 7), and turbidity (days 7 and 14), indicating that at the concentrations used in phase one of this study, these agricultural pesticides did not act synergistically. In phase two, higher levels of atrazine resulted in significant reductions in primary productivity, chlorophyll, green colonies, Bosmina, rotifers, and particulate phosphorus (>200 um and 20-200 um) on day 7. Bifenthrin had a negative impact on Bosmina, copepod nauplii, rotifers, primary productivity, chlorophyll, green colonies, and all particulate phosphorus fractions. In addition, 33% bluegill mortality was observed in treatment combinations with an average maximum concentration of 1/3150 ngL bifenthrin. The interaction effects found indicated that when either compound was introduced at ecologically realistic levels, its effects were essentially masked if the other toxicant was present at high concentrations

Planktivores and plankton dynamics : effects of fish biomass and planktivore type

Les auteurs ont quantifié les incidences de la biomasse et du type de planctophage dans le cadre d'une étude expérimentale en mésocosmes. Cette étude était conçue en fonction d'un plan factoriel d'expérience combinant cinq niveaux de biomasse de poisson (de O, à 75 g/m3) avec deux types de planctophage, soit l'alose à gésier (#Dorosoma cepedianum), un filtreur, et le crapet arlequin (#Lepomis macrochirus), un chasseur visuel. Une augmentation de la biomasse de poisson était accompagnée d'une baisse du nombre de cladocères, de cyclopoïdes et de chironomides et de la teneur en phosphore particulaire ...; inversement l'abondance de rotifères, de flagellés unicellulaires, d'algues vertes coloniales et unicellulaires, de diatomées pennées, la productivité primaire, la turbidité et les teneurs en chlorophylle a, en phosphore total ... ont augmenté ... Bien que la chaîne des cascades trophiques de l'alose à gésier et celle du crapet soleil soient différentes, la biomasse de poisson jouait un rôle plus important que le type de planctophage comme régulateur des communautés planctoniques et de la qualité de l'eau. (D'après résumé d'auteur

Piscivores, Trophic Cascades, and Lake Management

The concept of cascading trophic interactions predicts that an increase in piscivore biomass in lakes will result in decreased planktivorous fish biomass, increased herbivorous zooplankton biomass, and decreased phytoplankton biomass. Though often accepted as a paradigm in the ecological literature and adopted by lake managers as a basis for lake management strategies, the trophic cascading interactions hypothesis has not received the unequivocal support (in the form of rigorous experimental testing) that might be expected of a paradigm. Here we review field experiments and surveys, testing the hypothesis that effects of increasing piscivore biomass will cascade down through the food web yielding a decline in phytoplankton biomass. We found 39 studies in the scientific literature examining piscivore effects on phytoplankton biomass. Of the studies, 22 were confounded by supplemental manipulations (e.g., simultaneous reduction of nutrients or removal of planktivores) and could not be used to assess piscivore effects. Of the 17 nonconfounded studies, most did not find piscivore effects on phytoplankton biomass and therefore did not support the trophic cascading interactions hypothesis. However, the trophic cascading interactions hypothesis also predicts that lake systems containing piscivores will have lower phytoplankton biomass for any given phosphorus concentration. Based on regression analyses of chlorophyll�total phosphorus relationships in the 17 nonconfounded piscivore studies, this aspect of the trophic cascading interactions hypothesis was supported. The slope of the chlorophyll vs. total phosphorus regression was lower in lakes with planktivores and piscivores compared with lakes containing only planktivores but no piscivores. We hypothesize that this slope can be used as an indicator of “functional piscivory” and that communities with extremes of functional piscivory (zero and very high) represent classical 3- and 4-trophic level food webs

Feasibility and Acceptability of an Early Childhood Obesity Prevention Intervention: Results from the Healthy Homes, Healthy Families Pilot Study

BACKGROUND: This study examined the feasibility and acceptability of a home-based early childhood obesity prevention intervention designed to empower low-income racially/ethnically diverse parents to modify their children\u27s health behaviors. METHODS: We used a prospective design with pre-/posttest evaluation of 50 parent-child pairs (children aged 2 to 5 years) to examine potential changes in dietary, physical activity, and sedentary behaviors among children at baseline and four-month follow-up. RESULTS: 39 (78%) parent-child pairs completed evaluation data at 4-month follow-up. Vegetable intake among children significantly increased at follow-up (0.54 cups at 4 months compared to 0.28 cups at baseline, P = 0.001) and ounces of fruit juice decreased at follow-up (11.9 ounces at 4 months compared to 16.0 ounces at baseline, P = 0.036). Sedentary behaviors also improved. Children significantly decreased time spent watching TV on weekdays (P \u3c 0.01) and also reduced weekend TV time. In addition, the number of homes with TV sets in the child\u27s bedroom also decreased (P \u3c 0.0013). CONCLUSIONS: The findings indicate that a home-based early childhood obesity prevention intervention is feasible, acceptable and demonstrates short-term effects on dietary and sedentary behaviors of low-income racially/ethnically diverse children

Loper: A quadruped-hybrid stair climbing robot

Abstract-The purpose of this paper is to describe the Loper, a multi-purpose robotic platform under development at the University of Minnesota's Center for Distributed Robotics. Loper's unique Tri-lobe wheel design and highly compliant chassis make the platform especially suited for overcoming many of the challenges associated with search operations in urban settings. The mechanically simple design and use of commercially available components make Loper easily maintainable. The platform also features long operational time, onboard sensor processing, dedicated motion control, and four reconfigurable sensor bays

En Vivo: If We Call Them Will They Come? A Telephone-based Brief Motivational Enhancement Intervention Targeting TV Time

Introduction: The prevalence of overweight among children has doubled in the last twenty years, and Texas children rank near the top as the nation’s heaviest. Time spent television viewing may not only expose children to advertising for unhealthy foods, but may also take the place of physical activity