Leo R. Bodensteiner

Flowing Water: An Effective Treatment for Ichthyophthiriasis

Abstract Ichthyophthiriasis, or ich, is a disease of freshwater fish that is difficult to treat chemotherapeutically because the causative agent, Ichthyophthirius multifiliis, is protected by the hosts epithelium during much of its life cycle. In our experiments, a modified standard formalin treatment (25 mg/L for 4 h, 4 d/week) conferred partial protection but failed to prevent 40–70% mortality among channel catfish Ictalurus punctatus. A water velocity of 20.3 cm/min in 5-m-long raceways and a turnover rate of 2.5/h reduced mortality of ich-infected channel catfish fingerlings to less than 10%. A water velocity of 36.5 cm/min and a turnover rate of 4.5/h held mortalities to 7% and eliminated ich from the raceways. When turnover rate fell below 1.9/h (water velocity 85 cm/min, turnover rate > 2.1/h) resulted in no losses caused by ich during 2 years a...

Impacts of Riprap on Wetland Shorelines, Upper Winnebago Pool Lakes, Wisconsin

Isolation of causative factors has proved challenging in characterizing the physical, chemical, and biological effects of shoreline hardening on the nearshore environment because of logistical challenges in identifying comparable sites. Extensive shoreline hardening and interspersion with unaltered shores in the large, shallow lakes in central Wisconsin provide an opportunity to surmount this. We compared the effects of shoreline protection on wave climate, bottom topography and substrate, water quality, and plant and animal assemblages at five adjacent pairs of natural and armored (riprapped) shorelines. Armored shorelines were characterized by coarser, more compacted substrates with lower organic content; cooler temperatures with higher dissolved oxygen; and greater water clarity. Differences in physical and chemical properties likely influenced plant growth forms and fish feeding guild differences between riprapped and natural sites. For example, floating-leaved plants were more abundant and fish were nearly twice as abundant and were represented by larger individuals at natural versus armored shorelines. Substrate characteristics may account for the differences in water quality and plant and animal associations observed in this study. As shoreline property owners continue to install riprap as protection against erosion, we expect the nearshore environment and associated biological communities to increasingly reflect this practice.

Downstream Drift of Fishes in the Upper Mississippi River during Winter

ABSTRACT Many moribund and dead fish were found drifting in the main channel of the Mississippi River during late winter. A total of 3,574 fish representing 37 species were collected with an effort of 214 net-days in the tailwater habitat below Lock and Dam 13 and Lock and Dam 14 of the Mississippi River during February 1984 and March 1985. Bluegill (Lepomis macrochirus). channel catfish (Ictalurus punctatus), pumpkinseed (Lepomis gibbosus), freshwater drum (Aplodinotus grunniens), and gizzard shad (Dorosoma cepedianum) were the most abundant species, composing 87% of the total catch. Most of these were small fish, probably age 0 or age 1. Catch was not correlated with discharge, but was related to location of the net in the channel with more fish collected near the shores than the center.

Effects of repetitive formalin treatments on channel catfish juveniles

Abstract Channel catfish Icialurus punctatus ranging from 70 to 148 mm in total length were treated with formalin at a concentration of 25 μL/L for 4 h daily on four successive days each week over a 28-week period beginning in mid-September. Coefficients of condition (weight-tolength ratios) and histological examinations of gill tissues were used to evaluate health of fish exposed to formalin. Gill tissues of both formalin-treated and untreated fish showed effects typical of intensive culture, including hypertrophy, hyperplasia, and excess mucous secretion; no differences were found in gill morphometry between the two groups. Channel catfish periodically treated with formalin had a significantly higher coefficient of condition (P < 0.05) after 28 weeks and no indication of adverse effects attributable to formalin.

Historical Changes in Mid-Water Stands of Common Reed in the Winnebago Pool Lakes, Wisconsin

ABSTRACT Despite the tolerance of common reed grass to environmental extremes, mid-water stands in the Winnebago pool lakes of central Wisconsin appear to be diminishing. Formerly occupying shoreline locations, water level manipulations subsequent to dam construction beginning in the 1850s have isolated reed stands off shore. These stands have persisted but casual observations indicate that stand size has been declining. To address this perception we obtained an approximately decadal series of aerial photographs dating back to 1937 for four stands in Lake Poygan. Annual records were available for 1986–94. Using image analysis software, we determined shape and size metrics. Changes in stands varied widely, with areal losses ranging from 2% to 94%. The perimeter showed corresponding losses. Perimeter to area ratio and number of patches indicate that stand loss is characterized by increased fragmentation and shrinking patch size. The pattern of loss appears to proceed through an increase in irregularities along the perimeter, especially along edges facing the summer prevailing winds. This process exposes more of a patch to wind and wave action and eventually results in a division of the patch, culminating in periodic losses of the smallest patches. Despite an overall decrease in stand size, changes in size varied among the years of record with limited recovery occurring during some years.

Inventory and characterization of wetland habitat on the Winnebago Upper Pool Lakes, Wisconsin, USA: An integrated multimedia-GIS approach

An integrated, multimedia-geographic information system (GIS) approach to inventorying and characterizing thirty-nine wetland sites identified on the Winnebago Upper Pool Lakes in Wisconsin, USA was developed. Available black-and-white aerial photogrpahs recorded in 1937, 1957, and 1981 and color digital orthophotos of 2000 were employed as primary data sources to develop a spatio-temporal GIS database using a combination of digital image processing, GIS, Global Positioning System (GPS), and field survey techniques. Ten representative sites were selected to investigate the physical, chemical, and biological characteristics of the wetland habitat in the study area further. Multimedia information as text, graphics, ground photogrpahs, and digital video was then developed to highlight the ecosystem function and structure of those representative wetlands. A computer-based interactive multimedia system, consisting of a graphical user interface and a GIS application module, was constructed to allow easy access to both the spatial data sets and the multimedia information. Given the increased concern over environmental preservation, expansion of urban development, and agricultural land use, it is anticipated that the database will prove valuable for a series of management tasks. The integrated approach provides an innovative way for integrating, analyzing, and presenting wetland information, thus enabling truly interactive collaborations among resource managers, policy makers, reserachers, and stakeholders.

Ecosystem functions of mid-lake stands of common reed in Lake Poygan, Wisconsin

Mid-lake stands of common reed grass (Phragmites australis) have persisted in the shallow Winnebago Pool Lakes of east-central Wisconsin for more than 65 years. Previous research documented that the stands are declining in area with losses up to 94%. Our goal was to characterize the ecological functions of these stands, in part to assess the implications of their loss. To do so, we studied the common reed stands of Lake Poygan during summer, 1999. Common reed stands stabilized the silty/sandy substrate. Wind velocity and wave action were reduced on the downwind sides, and fine, organic sediment accumulated leeward relative to summer prevailing winds. Water clarity was greater on the leeward side. Within stands, dissolved oxygen was less variable, and temperature tended to be cooler. The 18 species of associated aquatic plants covered three or more times the area in the leeward side than windward side. Twenty-nine species of fish were found using the perimeter of the common reed stands. We expect that stand loss will be accompanied by loss of associated wetland vegetation, and the unique combination of habitat attributes afforded by these stands. The current conditions leeward of the stands suggest that stand loss will have a broader spatial effect on ecological characteristics, including fish populations, and thus the implications may be lakewide.

Shelter Occupancy by Mixed-Species Pairs of Native Signal Crayfish and Non-Native Red Swamp Crayfish Held in Enclosures

ABSTRACT Sheltering ability does not appear to confer an advantage to non-native red swamp crayfish (Procambarus clarkil) in a small, western Washington lake where the invader outnumbers the native signal crayfish (Pacifastacus leniusculus.) When paired with similar-sized non-native P. clarkii, P. leniusculus was adept at monopolizing limited artificial shelter inside enclosures placed on the bottom of Pine Lake. In these contests, the dominant crayfish or winner was typically the one with longer chelae, or, in the case of P. clarkii, the one that was sexually mature. Female crayfishes of both species also were adept at monopolizing the artificial shelter. Furthermore, irrespective of species and sex, when paired with smaller heterospecifics, large crayfish readily monopolized the artificial shelter. These results suggest that additional mechanisms besides shelter competition are contributing to the possible displacement of P. leniusculus in Pine Lake.

Design of a relative risk model regional-scale risk assessment with confirmational sampling for the Willamette and McKenzie rivers, Oregon

The estimation of regional risks due to multiple stressors is a frontier in environmental toxicology and risk assessment. We are conducting a regional scale ecological risk assessment of multiple stressors in the Willamette Valley, Oregon. The Willamette River drains an extensive agricultural area and forests of both the Coastal and Cascades mountains. The river also receives effluents from paper mills and urban wastewater treatment facilities. A major tributary of the Willamette is the McKenzie River. The McKenzie watershed, which extends into the Cascade Mountains, is extensively forested. Stressors in this watershed include alterations in the landscape due to the harvest of trees, the infrastructure required for the logging, modification of the river or stream banks, and inputs due to contamination by localized urban and non-point sources. We are using the relative risk model (RRM) for ecological risk assessment developed by Wiegers, Landis, and colleagues to combine multiple stressors and receptors in a regional context. The first step in the RRM process is the establishment of assessment endpoints for the particular area and the placement of the endpoints in the landscape. Next, the method involves the development of risk matrices that combine diverse stressors and habitats within the region with numerical ranks. We have broken the McKenzie and Willamette watershed study areas into 13 risk regions and have mapped the locations of the point sources and are incorporating land use data. Using a variety of documents we have established the assessment space and are developing criteria for ranking stressors and habitats. We have also initiated a 3-year field research activity to confirm the risk predictions within the main channel. The sampling sites correspond to the risk regions of the RRM. The sampling program will characterize the population density and structure of the fish assemblage and measuring the health of the individual fish.

Chromium in Rainbow Trout from an Exposed Dunite Formation, Twin Sisters Mountain, Washington

ABSTRACT Twin Sisters Mountain, Washington, is dominated by a dunite rock formation containing the mineral chromite (iron magnesium chromium oxide: (Fe, Mg)OCr2O3). We sampled rainbow trout and collected water samples from Howard Creek, a Twin Sister watershed. From 0.5 to 3.7 mg Cr/kg fresh weight was found. However, concentration of Cr was not related to fish size. Since Cr was not detected in the water, the route of uptake by fish is likely through ingestion. Since the range of concentrations of Cr in these fish overlaps with those that have been found to adversely affect health, these fish may have adapted to tolerate Cr.