Effects of fish density, identity, and species richness on stream ecosystems.

Stream ecosystem properties and functions are important because they provide services such as water purification, oxygen production, and carbon fixation that help sustain life. Aquatic organisms can affect these properties and functions through different pathways linked to a species trophic and functional characteristics. It is necessary to understand how these ecosystem effects vary among taxa because as aquatic biota change as a result of random, natural, or anthropogenic influences, ecosystems properties and functions are likely to be affected.This research suggests that the population size, the identity of species in the assemblage, as well as the number of species making up the assemblage can be important factors affecting stream ecosystem properties and functions. Chapters 1--3 were conducted in artificial stream mesocosms, and may have limited applicability to natural stream ecosystems where a variety of abiotic factors can influence ecosystems. In Chapter 4, I tested the ecosystem effects of three fish species from different functional groups on PPR, benthic algae biomass (as chlorophyll-a), and benthic invertebrate density in a natural stream ecosystem using field enclosures. Treatments were Blackstripe Topminnow (Fundulus notatus), a surface insectivore; Longear Sunfish (Lepomis megalotis), a watercolumn insectivore; Orangethroat Darter (Etheostoma spectabile), a benthic invertivore; and a fishless control. Primary productivity was greater in all enclosures with fish than in enclosures without fish. Relative to control enclosures, benthic algae biomass was not different in Blackstripe Topminnow treatments, but was greater in Longear Sunfish treatments on both sample days, and was greater in Orangethroat Darter treatments on day 15. Benthic invertebrate abundance was not affected by any of the fish treatments. These data agree with results from previous mesocosm experiments. Thus, despite the limited realism of stream mesocosms, patterns observed in mesocosm experiments are likely to occur in natural stream ecosystems. (Abstract shortened by UMI.)Fishes are important consumers in stream ecosystems, having important regulatory roles for many ecosystem properties and functions. In this dissertation, I addressed the effects of fishes on stream ecosystems from three perspectives. I asked (1) if fish ecosystem effects were dependent on local fish density, (2) if fish effects were caused by different species-specific food web pathways, and (3) if co-occurring fish species had facilitative effects on ecosystems when in more specious assemblages

First Arkansas Records for Bigscale Logperch Percina macrolepida Stevenson (Pisces: Percidae), with Comments on Habitat Preference and Distinctive Characters

Fish samples were collected with seines and rotenone from 21 localities representing five major habitat types along the Red River in Arkansas. The bigscale logperch, Percina macrolepida, was found at 11 of those sites, providing the first records ofthat species from the state. The primary preferred habitat parameters for bigscale logperch are no current, a sand and/or silt substrate, and a water depth of 1.0-2.0 m. Percina macrolepida is morphologically very similar to the widespread and common logperch, P. caprodes, but can be distinguished from all forms of that species in Arkansas by a combination of characters. Snout shape and the presence of scales on the breast, prepectoral area, and along the posterior edge of the preopercle in P. macrolepida are the most useful distinguishing features

Remnant Coal Detection System

This paper describes the development and successful implementation of a system designed to detect coal deposits remaining in coal train wagons after unloading (dumping). These undesirable coal deposits constitute both small residual amounts of “carryback”, but also larger “hang-ups” of significant volume that have failed to discharge. The system was originally developed simply to detect and record volumes of carryback, as part of an effort to characterise the extent of the problem for the coal transport industry, but was then enhanced to provide real-time feedback of large hang-ups so that they could be discharged prior to the wagons exiting the dump station. The paper describes the hardware and processing systems used in the system, including the different strategies employed to ensure a reliable detection system. The system has now been installed and operated in a production environment at three dump stations across two different coal terminals, and a case study of the results from one of these dump stations is presented. Automating remnant coal detection at dump stations provides short interval control to minimise potential hazards and downtime, and historical data that may be integrated into existing data platforms and analysed for productivity, environmental, and safety planning insights

Scanning radar system for machine guidance

This paper documents an application of a scanning microwave radar system that has been developed by the CSIRO Mining Technology group as an aiding sensor for machine guidance in a mining environment. In this application, radar imaging is considered as a vital alternative to other technologies such as optical imaging based on laser technology, because the imaged environment is characterized by high levels of airborne and surface dust. In this case, the microwave radar offers a higher level of immunity against fine particle interference than an optical system. This is an attractive solution provided that a lower resolution image is acceptable. The developed scanning radar system combines a mechanical pan-tilt scanning platform and a 26 GHz monostatic radar unit. The prototype system is employed in the field for the purpose of collision detection on a shiploader boom. Raw data from this unit is processed to allow comparison with corresponding laser scanner point data, initially for the 2D case of measuring the distance-to-deck from the shiploader boom. The 2D results are encouraging. Based on these positive results, a software interface featuring a 3D display of detected targets is developed

A Major Step Forward in Continuous Miner Automation

Progress on a major research and development project undertaken by the CSIRO Mining Technology Group to advance the automation capability of continuous mining equipment in underground coal mining operations is described. The aim is to increase the overall rate of roadway development as well as providing a safer working environment for underground mine personnel. The outcomes achieved at the half-way mark of this ACARP funded three-year research and development project are reported. Details of the technical developments undertaken towards demonstration of a “self-steering” capability to enable a Continuous Miner to automatically maintain a given mining heading and mining horizon under production conditions are provided. Reported outcomes include the means to accurately determine both the location and orientation of a Continuous Miner in real-time using a combination of a navigation-grade inertial navigation unit, Doppler radar and optical flow technologies. Comprehensive performance evaluations have been conducted using a scaled skid-steer mobility platform and results achieved to the present stage of the project indicate that the required automated self-steering functionality is achievable under production conditions. The project outcomes represent an important move towards achieving a step change improvement in underground roadway development practice

Radar target recognition using selective resonance excitation

Resonance-based radar target recognition is premised on the observation of natural resonant frequencies so that target discrimination and classification can occur. This implies the use of ultra-wideband (UWB) radar in order to excite a sufficiently wide range of target frequencies, however developing practical UWB radar systems is a significant challenge. Furthermore, due the relative weakness of the late-time resonant target response, it is often not possible to isolate the resonant frequencies under realistic noise conditions. To mitigate these limitations, this paper examines the feasibility of selective excitation of resonant frequencies using more traditional (narrow-to-medium band) excitation. Simulated target results are presented for which resonant frequencies are extracted, and the efficacy of selective excitation of these resonances is demonstrated

Radar target discrimination for infrastructure-based navigation

The application of radar target identification to an autonomous vehicle navigation problem is described. Using the well-known and unvarying physical characteristics of certain frequently occurring infrastructure features in the environment (an underground coal mine), target discrimination by means of complex natural resonance extraction is undertaken to identify the desired structures and discriminate non-target clutter. Results are presented that demonstrate the feasibility of the method for identifying a particular mine infrastructure feature while rejecting non-target structures of similar dimensions. Once these targets have been identified, they can be used as navigation waypoints to correct drift in the autonomous guidance systems onboard the vehicle

Radar target identification by histogram analysis of resonant frequencies

A novel technique is presented for isolating the late-time resonant frequencies of specific radar targets using statistical analysis of repeated target scattering responses. Through the application of techniques for multimodal histogram analysis, dominant resonant frequency patterns for simulated and measured targets are developed to provide a reliable basis for identification regardless of target orientation, even in the presence of significant noise. Results are demonstrated for a practical target identification application that arises in underground coal mining